Master’s thesisPhysical Geography and Quaternary Geology, 60 Credits

Department of Physical Geography

Diatom distribution in the lower Save River, Mozambique

Taxonomy, salinity gradient and taphonomy

Marie Christiansson

NKA 1562016

Preface

This Master’s thesis is Marie Christiansson’s degree project in Physical Geography and

Quaternary Geology at the Department of Physical Geography, Stockholm University. The

Master’s thesis comprises 60 credits (two terms of full-time studies).

Supervisor has been Jan Risberg at the Department of Physical Geography, Stockholm

University. Examiner has been Stefan Wastegård at the Department of Physical Geography,

Stockholm University.

The author is responsible for the contents of this thesis.

Stockholm, 11 September 2016

Steffen Holzkämper

Director of studies

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Abstract

In this study diatom distribution within the lower Save River, Mozambique, has been

identified from surface sediments, surface water, mangrove cortex and buried sediments.

Sandy units, bracketing a geographically extensive clay layer, have been dated with optical

stimulated luminescence (OSL). Diatom analysis has been used to interpret the spatial

salinity gradient and to discuss taphonomic processes within the delta. Previously, one study

has been performed in the investigated area and it is of great importance to continue to

identify diatom distributions since siliceous microfossils are widely used for

paleoenvironmental research. Two diatom taxa, which were not possible to classify to

species level have been identified; Cyclotella sp. and Diploneis sp. It is suggested that these

represent species not earlier described; however they are assigned a brackish water affinity.

Diatom analysis from surface water, surface sediments and mangrove cortex indicate a

transition from ocean water to a dominance of freshwater taxa c. 10 km upstream the delta

front. Further, ratios between marine/brackish taxa for samples from surface water and

surface sediments do not correspond. It is therefore suggested that diatoms in surface

sediments underestimate prevailing salinity conditions in water. In the investigated area

extensive taphonomic processes seem to have large impact on diatom frustules in sediments

and may bias interpretations. Therefore it is recommended to carefully investigate geology,

geomorphology and vegetation before diatom analysis is applied in studies of delta

paleoenvironments.

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Table of contents Abstract ................................................................................................................................................... 1

Table of contents ..................................................................................................................................... 2

1. Introduction ........................................................................................................................................ 3

1.1 Objectives ...................................................................................................................................... 6

1.2 Background ................................................................................................................................... 6

1.2.1 Salinity stratification .............................................................................................................. 6

1.2.2 Diatoms .................................................................................................................................. 7

1.2.3 SEM/ESEM ............................................................................................................................. 9

1.2.4 OSL ......................................................................................................................................... 9

2. Description of the investigated area ................................................................................................ 10

3. Methodology..................................................................................................................................... 13

3.1 Siliceous microfossils................................................................................................................... 15

3.2 ESEM ........................................................................................................................................... 19

3.3 OSL .............................................................................................................................................. 19

4. Result and interpretation ................................................................................................................. 19

4.1 Surface water samples ................................................................................................................ 20

4.2 Surface sediment samples .......................................................................................................... 21

4.3 Mangrove cortex samples ........................................................................................................... 21

4.4 Buried sediments ........................................................................................................................ 28

4.5 Taxonomic remarks ..................................................................................................................... 38

5. Discussion.......................................................................................................................................... 41

5.1 Taxonomy .................................................................................................................................... 41

5.2 Salinity gradient .......................................................................................................................... 42

5.3 Taphonomy ................................................................................................................................. 44

5.4 OSL and radiocarbon dating ........................................................................................................ 49

5.5 Future studies ............................................................................................................................. 50

6. Conclusions ....................................................................................................................................... 51

7. Acknowledgement ............................................................................................................................ 52

8. References ........................................................................................................................................ 53

9. Appendix 1 ........................................................................................................................................ 69

10. Appendix 2 ...................................................................................................................................... 71

11. Appendix 3…………………………………………………………………………………………………………………………………76

12. Appendix 4…………………………………………………………………………………………………………………………………80

13. Appendix 5…………………………………………………………………………………………………………………………………81

14. Appendix 6………………………………………………………………………………………………………………….................82

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1. Introduction

Research on past climate is required to forecast future global climate changes (e.g. Palmer &

Abbott, 1986; Shennan et al., 1993; Denys and de Wolf 1999; Zong & Horton, 1999; Church

et al., 2013). One aspect implies changes of the global mean sea level, which can involve

either a rise or a lowering affecting coastal environments, e.g. deltas (Tamura et al., 2012;

Church et al., 2013). A rising sea-level involves effects on wave-induced erosion,

tides and currents influencing shorelines and mangrove forests holding complex ecosystems

(Nicholls & Cazenave, 2010). A lowering could imply an increased erosion by fluvial

and terrestrial processes combined with effects on floras and faunas. As the global sea-level

has fluctuated over time, especially during the Quaternary (Lowe & Walker, 1997), changes

can be traced in coastal environments (Woodroffe, 1990). To increase knowledge of the

effects from approaching eustatic sea-level rise, past fluctuations should be

elaborated. Paleoenvironmental research is often hampered by chronological drawbacks (cf.

Andrews et al., 1999; Wang et al., 2013; Bala et al., 2016). Deltaic sediments have an

advantage since they may be dated by optically stimulated luminescence (OSL) as a

complement to radiocarbon dating (cf. Bishop et al., 2004; Zhao et al., 2008; Erginal et al.,

2009).

One potential approach to study paleo-climate and paleo-environment is analysis of siliceous

microfossils, mainly diatoms (e.g. Simonsen, 1969; Palmer & Abbott, 1986; Vos & de Wolf,

1993:1; Espinosa, 1994; Denys, 1999; Denys and de Wolf, 1999). As living diatoms are

sensitive to changes of salinity, pH and nutrition (Cooper, 1999; Jiang, et al., 2001; Hassan, et

al., 2006) and fossil frustules (shells) in sediments normally are well preserved (Ferguson

Wood, 1967), they may indicate environmental changes such as tidal currents, flooding

events and sea level fluctuations (Swan, 1983; Vos & de Wolf, 1988). Previous studies have

shown benefits of using diatom analyses to reconstruct these changes in delta environments

(cf. e.g. John, 1987; Zalat, 1995; Zong et al., 2009; Ellison, 2008; França et al., 2015). To

improve the interpretation of fossil diatoms, further investigations on recent assemblages

are beneficial as they are a key to understand fossil communities (John, 1987; Castro et al.,

2013; Zong & Horton, 1998; Zong et al., 2006). This study is thus focusing on diatom analysis

from surface material from the lower Save River, Mozambique, and factors that may affect

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the interpretation of past diatom compositions. Here, the lower Save River include the delta

area and c. 70 km upstream.

Most of the global stratigraphic diatom investigations are from the northern hemisphere

(Holmgren et al., 2012). Along the east African coast, diatom studies are most frequently

conducted in South Africa (e.g. Schuette & Schrader, 1981; Talbot & Bate, 1987; Abrantes,

2000). Norström et al. (2012) conducted a paleoenvironmental study on the Macassa Bay,

Mozambique, which is located c. 150 km south of the investigated area. At present,

Massuanganhe et al. (2016a) is the only study from the Save River delta.

Parts of the Save River delta are occupied by mangrove forest, which is habitat for complex

ecosystems (e.g. Lugo & Snedaker, 1974; Burchett et al., 1984; Smith et al., 1991; Ball &

Pidsley, 1995; Lee, 1999). This vegetation is currently experiencing an increasing degradation

(Woodroffe & Grime, 1999; Santos et al., 2014; Chaudhuri et al., 2015), argued to be caused

by human activities (Bandeira et al., 2009; Erftemeijer & Hamerlynck, 2015) and/or by

changing coastal dynamics as a result of eustatic sea level fluctuations (e.g. Ellison &

Stoddart, 1991; Fujimoto et al., 1996; Behling et al., 2004; Reinhardt et al., 2010; Srivastava

& Farooqui, 2013). Therefore, researchers of previous studies on mangrove wetland

dynamics (e.g. Woodroffe et al., 1985; Ellison & Stoddart, 1991; Fujimoto et al., 1996)

encourage further studies on coastal areas to increase the understanding of processes

within these environments (Nicholls et al., 1999, Nicholls, 2004, Gedan et al., 2011).

Diatom frustules can be affected during sedimentation and after accumulation due to their

sensitivity to physical, biological and chemical changes, i.e. taphonomy (Round et al., 1990;

Bennion, 1995; Hillebrand & Sommer, 2000; Riviera & Diaz, 2004; Hassan et al., 2006;

Korhola, 2000). This phenomenon refers to processes affecting diatom frustules after their

death. Dynamic environments, such as deltas, imply several of these mechanisms, which can

bias the interpretation (Brzezinski et al., 1999; Kato et al., 2003; Ryves et al., 2013).

Sediment traps are often used to determine processes on taphonomy in an area (e.g. Kato et

al., 2003; Cameron, 1995). Comparisons between surface and fossil diatom taxa can,

however, also indicate taphonomic mechanisms (cf. Barker et al., 1999; Sawai, 2001). Ryves

et al. (2009) emphasize the importance of using living diatom assemblages (biocoenosis) and

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fossil communities (thanatocoenosis) to analyze taphonomy, i.e. the connection between

present environment and the fossil signal. In tidal environments processes as erosion,

resuspension and redepositing of sediments occur on diurnal basis (de Blij et al., 2004).

Taphonomy involves e.g. breakage and/or repositioning of frustules. Breakage can occur

during both reworking and compaction of sediments. Biological and chemical processes

mainly include presence of roots and their uptake of dissolved silica. Dissolution of silica in

soil increases during high temperatures and bacterial activity (Struyf et al., 2005). Diatom

frustules can then be affected by chemical corrosion in varying extent (cf. Massuanganhe et

al., 2016a) as they have different thicknesses, thus thinly silicified diatoms are less resistant

(Castro et al., 2013; Ryves et al., 2013; Brzezinski et al., 1999; Jørgensen, 1955; Lewin, 1961).

Fossil diatom frustules can be of autochthonous or allochthonous origin. Identification of

origin of certain species may be useful in environmental studies, as it facilitates

interpretation and understanding of geomorphological processes. Marine planktonic species

are known to be allochthonous and represent the tidal water influence. Benthic freshwater

taxa are proposed to be autochthonous and characterize the input from the river (Vos & de

Wolf, 1993:1). Simonsen (1969) suggests benthic species to be autochthonous thus providing

the most reliable information. Taphonomic processes do, however, aggravate analysis of

allochthonous and autochthonous species (Andrews, 1972; Beyens & Denys, 1982; Vos & de

Wolf, 1993:1). Therefore, further studies of surface and fossil diatom assemblages are

required to increase knowledge about taphonomy and effects on diatom frustules.

Furthermore, there is a widespread problem with diatom taxonomy (species identification)

and corresponding ecology (Mann, 1999). To ensure accurate interpretations it is

recommended to carefully study the morphology under both light microscope and with SEM

Scanning Electron Microscope). In general, the study of environmental conditions in an

investigated area can be used to enhance literature information (John, 1987; Castro et al.,

2013; Zong & Horton, 1998; Zong et al., 2006; Mann, 1999).

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1.1 Objectives

The main aims of present study are to increase knowledge about:

(i) diatom distribution in the lower Save River,

(ii) diatom taxonomy and ecology,

(iii) intrusion of marine water into the lower Save River,

(iv) taphonomic processes affecting the diatom flora.

1.2 Background

This study is an off-spring of the doctoral thesis by Elidio Massuanganhe (2016). In his thesis,

Massuanganhe used siliceous microfossils to evaluate geomorphological and environmental

dynamics within the Save River delta. His results, however, showed only scattered

occurrences of diatoms in the investigated sequences and therefore taphonomic processes

were discussed. In June 2015, an opportunity was opened to join during the field trip to the

area. In connection with this, a number a samples were collected in order to receive more

information on diatom distribution and taphonomic processes.

Four subjects are presented here as they are essential for the forthcoming results and

discussions.

1.2.1 Salinity stratification

Salinity in seawater is varying with depth as density increases with greater amounts of

dissolved salt. Between the surface water of low salinity and the saline deep water there is a

layer of rapid change in salinity, i.e. the halocline (Trujillo & Thurman, 2014). Accordingly,

different local stratification patterns arise in coastal areas. In dynamic environments such as

deltas, a vertical and horizontal salinity gradient is present from the river to the ocean

(Cameron & Pritchard, 1963; Pritchard, 1967). The stratification is fluctuating depending on

effects from mainly tides, waves, currents, rainfall in the catchment area and amount of

evaporation in the delta area. Amounts of suspended sediment do, however, also influence

the stratification since it increases the density (Semeniuk, 2016).

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In delta environments with perennially flowing rivers, the landward part of the water can

consist of almost entirely freshwater. If the river flow is seasonally, a mixture from fresh- to

marine water is present. During intense river flows, plumes of freshwater can reach out into

the ocean. The stratification in the delta is thus depending on both seaward processes and

the features of the river (Haas, 1977; Geyer & Farmer, 1989; MacCready, 1999; Semeniuk,

2016).

During low tide the water in deltas is highly stratified with an almost vertical halocline and a

thinning of the freshwater layer towards the delta front. When high tide is present, marine

water is pressed further into the river channel and the halocline slightly decline landwards

(Largier, 1986; Largier, 1992). Flooding events imply a halocline with a steep gradient

landwards as freshwater pressure is high. During both high tide and floods, the freshwater

and brackish/marine water is mixed in a greater extent than during low tide (Largier &

Taljaard, 1991; Semeniuk, 2016). Estuaries with several river channels leading to the ocean

increase the complexity of mixing and stratification even more (Semeniuk, 2016).

1.2.2 Diatoms

These organisms have been studied since the late 18th century. The initial taxonomy work

was done during the early 19th century by Müller, Nitsch and Gray. Further fundamental

research was performed by e.g. Ehrenberg, Kützing, W.W. Smith, Gregory, Greville, Ralfs,

Donkin, Grunow, P.T. Cleve, A. Cleve-Van Heurck and Hustedt (Ferguson Wood, 1967).

Diatoms are siliceous microfossils and have cell-walls composed of amorphous hydrated

silica. They have two shells (also named frustules), which are attached to each other (Lowe &

Walker, 1997). The outer shape of the diatom frustule is divided into two groups; pennate or

centric. Pennate diatoms have bilateral symmetric valves and centric are radial symmetric.

Centric diatoms cannot move by themselves; however, some pennate diatoms are capable

of moving by the raphe structure (Round et al. 1990; Krammer & Lange-Bertalot, 2000).

These unicellular algae belong to Bacillariophyta (Brasier, 1980; Round et al., 1990), which is

the most species-rich group (Mann, 1999). The length of the frustules is generally between c.

5 and 2000 µm, but size can diverge, especially during the early and late stages of the life

cycle (Brasier, 1980; Round et al., 1990; Lowe & Walker, 1997).

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Siliceous microfossils live in aquatic and semi-aquatic environments, both as planktonic and

benthic. Planktonic species are suspended in the pelagic zone and benthic are attached to

sediment surfaces and vegetation in the benthic zone. There are, however, benthic diatoms

which can be brought up into the plankton habitat through e.g. currents and winds. These

are referred to as tychoplanktonic species (Ferguson Wood, 1967; Round et al., 1990).

Diatoms can also be redeposited from their habitat through for example birds (Atkinson,

1980; Figuerola & Green, 2002) and boats (Hallegraeff & Bolch, 1992).

Access to light is an essential factor for diatoms. They are photosynthetic and grow in the

photic zone (Round et al., 1990). Diatom blooms, i.e. flourish of species, occur during

favorable conditions such as during the spring. Conditions, which imply access to light,

optimal temperature and pH, and access to silica, nitrogen and phosphorous are beneficial

for diatom reproduction (Furnas, 1990; Round et al., 1990; Martin-Jézéquel et al., 2000;

Litchman et al., 2008).

Diatoms have a significant role in the global carbon, silica and oxygen cycles and therefore

contributes to the global ecosystem primary production (e.g. Hsaio, 1988; Cota et al., 1991;

Glud et al., 2002). Furthermore, diatoms are alone accountable for a quarter of the inorganic

carbon (e.g. CO2) fixed in the oceans every year, nevertheless researchers have not clarified

all aspects of the complex processes which fix the inorganic carbon (Granum et al., 2005).

During phases of cell division in the diatom life cycle, silica is naturally dissolved and partly

used by other organisms and vegetation (Mann, 1999; Smetacek, 1999). When the diatom

cell divide, cell walls usually become significantly thinner as energy and silica are used to

form new frustules (Ehrlich & Newman, 2008). Diatoms reproduce through vegetative

division, which implies a cell division inside the parent cell. Therefore, daughter cells are

significantly smaller than parent cells. The new cells have one new frustule, which is formed

during the division, and one from the parent. Reduction of size of the parent cell thus occurs

during every reproduction. The life cycle of a diatom thus implies several stages of frustule

size, which is termed “size reduction series” and means young and old diatoms have

frustules reduced in size. This is an important factor to consider during diatom analysis

(Round et al., 1990; Falkowski & Knoll, 2007; Hense & Beckmann, 2015).

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1.2.3 SEM/ESEM

Scanning Electron Microscopes (SEM) are microscopes which allow magnification to atomic

level. In SEM the chamber, where the sample for analysis is placed, is a gaseous vacuum

environment. Instead of light, which is used in a light-microscope, electrons are used in an

SEM to reflect the surface of the specimen. The microscope has a primary concentrated

electron ray which is used towards the sample. The secondary rays are collected and create

a detailed visualization of the surface of e.g. diatoms (Danilatos, 1993).

Environmental Scanning Electron Microscope (ESEM) has usually the same basics

specifications as SEM, but ESEM tolerates even higher pressure in the chamber. It also allows

the device to operate at conditions other than only high vacuum by using different sets of

detectors (Danilatos, 1988). SEM and ESEM are frequently used for investigate frustule

structures and identification to species level (cf. e.g. Siver et al. 2003; Ponander & Potapova,

2007).

1.2.4 OSL

Optically Stimulated Luminescence (OSL) dating relies on measurements of light

(luminescence) emitted from light sensitive electron traps in crystals, where quartz and

feldspar comprises the most commonly used mineral types (Lowe & Walker, 1997). OSL ages

ideally represents the timing of burial or last exposure to sunlight of sedimentary deposits

After burial the luminescence signal gradually accumulates due to background radiation

occurring in the surroundings of the deposit. When the minerals are exposed to sunlight the

luminescence signal is zeroed (Yukihara & McKeever, 2011; Preusser et al., 2008). For dating

applications, the luminescence signal is released in laboratory conditions through artificial

stimulation, during which the signal is measured and further related to a radioactive dose.

Stimulation with green light is typically used for quartz, whereas infrared light are used for

feldspar (Lowe & Walker, 1997; Yukihara & McKeever, 2011; Preusser et al., 2008). The

luminescence measurements are used to determine the amount of radiation the sample has

been exposed to during time of burial. For age calculations, the amount of dose is divided

with the rate of radioactive energy acting on the sample per year, also termed dose rate. The

dose rate can be measured in field or in laboratory (Preusser et al., 2008).

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The luminescence signal can, however, be incompletely zeroed prior to deposition of the

sediment, also referred to as incomplete bleaching. This occurs when the minerals have not

been sufficiently exposed to sunlight, which results in an overestimation of the age of burial

since a signal is preserved. Transport by and/or deposition in water may also increase the

risk for incomplete bleaching. During age calculation, it should be considered whether these

factors are likely to have affected sediments and certain statistical approaches can detect if

samples are incomplete bleached. If so, several measurements of the absorbed dose are

made to investigate the dose distribution (Bailey & Arnold, 2006). Furthermore, sedimentary

water content in the samples collected for OSL dating can influence the dose rate and could

imply uncertainties for the final age.

2. Description of the investigated area

The investigated area includes mainly the Save River delta but also a sampling site c. 70 km

up-streams, located in the south-central part of Mozambique (Figure 1). The catchment area

for Save River basin is located mainly in the eastern parts of Zimbabwe and covers c. 102,000

km2 (Massuanganhe, 2016). With its classical triangular shape (de Blij et al. 2004) the delta

shows similarities, however minor, with the Nile Delta.

The distance of the Save River deltaic plane is c. 20 km from its front to the pre-Holocene

bedrock. Caused by south north coastal current it has an elongated shape with a distance of

c. 65 km (cf. Massuanganhe et al. 2016b, Figure 1). The investigated area westward from the

deltaic plane represents the feeding river channel. The bedrock in the upper part of the

drainage system consist mainly of intrusive igneous rocks (Le Maitre, 2002; Schlüter, 2006),

which cause acid water conditions. The formation of this sedimentary basin was initiated

during the Carboniferous and the Triassic periods (c. 350- 200 Ma ago) (McElhinny & Briden,

1971; Salman & Abdula, 1995). The lower part of the drainage system and the delta area is

underlain by calcareous bedrock, which implies alkaline environments. The Save River Delta

most likely formed during early Holocene epoch (c. 7-8 cal. yrs BP) when the mean sea level

reached approximately the present situation (Fleming et al., 1998; Milne et al., 2005).

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The East African rift system is located north of the Save River Delta. It is c. 6000 km long

reaching Ethiopia in the north. Several earthquakes have occurred during the last decade

along the distal parts of the Save River, indicating tectonic activity in the surrounding area

(Chorowicz, 2005). Macassa Bay c. 120 km south of the investigated area has, however, been

tectonically stable during the late Quaternary period and no activity has been recognized

during the Holocene epoch along the southeastern African coast (Miller et al., 1993; Ramsay,

1995; Ramsay & Cooper, 2002).

Figure 1. An overview map of the investigated area. A – Shows the location of the investigated area in southeastern Africa. B – The subareas within the investigated area and M32, which is located further upstream the Save River. Subarea 1 shows the lower part of the Save River delta, Subarea 2 shows the upper part of the delta and Subarea 3 shows the riverine part. C – SPOT image taken in 2011 with red-green-blue band combination showing landscape structures. The darker red color in the coastal area indicates mangrove forest distribution. Sampling sites are labelled M1-32. M16 and M27 are not shown as these sites are not used in the study. Color and shape of site symbols indicate collected sample type. “M” represents sites sampled for the present study and “P” sites used by Massuanganhe (2016). White rectangles display the three subareas.

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The coastline of Mozambique is a tidal environment and influenced by southeastern winds

and northward ocean currents (Sete et al., 2002) transporting large amounts of sand. When

deposited, sand dunes and spits pointing northward are formed.

Mozambique has a humid equatorial climate with dry winters (de Blij et al., 2004) and the

rainy season is from October to March (De Boer et al., 2000; Yang et al., 2015). Local

evaporation increases during February to April when the sea surface temperature reaches its

maximum (Rouault, 2003; de Blij et al., 2004).

Extreme rainfall within the drainage area cause flooding events in the investigated area and

further up-stream the river channel. These, together with the tides, form local differences in

salinity stratification in the water (Semeniuk, 2016). The most severe flooding events

commonly co-occur with tropical cyclones. Several major cyclones have affected the area

during the last 15 years. During floods, the transport and reworking of sediment in the Save

River and its delta increase (Massuanganhe et al., 2015). These events and tides amplitudes

of c. 4.5 m (Sete et al., 2002) cause the investigated area to be highly dynamic concerning

geomorphological processes.

Parts of the Save River deltaic plane are occupied by mangrove forest (Figure 2), an

ecosystem with rich biodiversity. This type of vegetation is well adapted to rapid changes of

e.g. temperature and salinity, which are natural stressors present in coastal environments

(Kathiresan & Bingham, 2001). Mangrove thrives in anoxic mud and has characteristic roots,

which are partly growing above the water surface to breathe. The roots are efficient

sediment traps and form layers of fines with high organic content (Scoffin, 1970; Kristensen

et al., 2008). Intense erosion and reworking of sediment in coastal environments do,

however, occasionally cause mangrove dieback (Alongi, 2002; Massuanganhe et al., 2016a).

During field work for the present study mangrove forest occurred from the delta front to

approximately M13 (Figure 1). Mangrove forests are commonly halophytes, resulting in high

tolerance to a wide range of salinity and high levels of salt in the water (Thom, 1967;

Fujimoto et al., 1996), however, they are mostly found in estuaries and rarely in freshwater

environments (Gilmore & Snedaker, 1993). The pH in mangrove sediments and soils is

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usually around 7, but can range between 4 and 8 (Middelburg et al., 1996; Boto &

Wellington, 1984; Joshi & Ghose, 2003).

Figure 2. Mangrove forest in the Save River delta with characteristic roots. Parts of the root systems grow above the water surface to increase uptake of oxygen as mangrove thrive in anoxic mud.

3. Methodology

The material analyzed and interpreted in the present study was collected by the author in

the lower Save River (Figure 3). All together 32 sites were visited, however, samples M16

and M27 are not included. M16 was destroyed during transportation to Sweden and M27

was collected as it was most likely aeolian sediment, later considered to be irrelevant for the

aim of this study (Table 1). To give a comprehensive distribution of diatoms in the lower

Save River, diatom records from sites P1, P2, P3, P6 and P8 (Massuanganhe et al., 2016a) is

incorporated and compared with records from the present study. P1, P2, and P3 have the

same coordinates as M20, M14 and M24 (Table 1). At site P2/M14 buried sediments have

been collected by Elidio Massuanganhe and the author of this study. To compile a further

comprehensive study, diatom records from these two sites have been combined. Samples

from the present study and Massuanganhe et al. (2016a) are equally labeled according to

the site names. Samples/sites beginning with “M” are consequently collected/visited by the

author, and samples beginning with “P” are collected/visited by Elidio Massuanganhe.

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Table 1. Details of visited sampling sites. Samples at M sites are collected by the author of this study and Elidio Massuanganhe has collected the sediments from P sites. Coordinate differences for P1/M14, P2/M20 and P3/M24 could be related to erosion between sampling events.

Site Latitude (South)

Longitude (East)

Character of sample*

Physiography Classification of sediments**

M1 20° 57' 36.72" 35° 07' 30.47" SW, SS, MC Shoreline Sand

M2 20° 57' 40.96" 35° 07' 24.31" SW, SS, MC Back-swamp Fines

M3 20° 57' 46.69" 35° 06' 57.02" SW, SS, MC Sandbank middle of river channel Sand

M4 20° 57' 43.23" 35°06' 27.54" SW, SS, MC Riverbank. SW; M4a: Riverside, M4b: Middle of river channel

Fines

M5 20° 57' 43.48" 35° 05' 52.30" SW, MC Sandbank middle of river channel Fines

M6 20° 57' 6.731" 35° 04' 44.44" SW, MC Riverbank Fines

M7 20° 53' 51.82" 35° 05' 41.96" SS Shoreline Fines

M8 20° 54' 37.00" 35° 04' 13.37" SS Riverbank Fines

M9 20° 55' 40.94" 35° 03' 56.05" SW, SS, BS, OSL Riverbank Fines and sand

M10 20° 57' 35.74" 35° 03' 34.52" SW, SS River bay Fines

M11 20° 58' 05.66" 35° 03' 8.89" SW, SS Riverbank Sand

M12 20° 58' 08.01" 35° 03' 11.09" SS SS; M12a: Overflow area, M12b: River channel

M13 20° 58' 37.59" 35°02' 38.54" SW Riverbank Sand

M14 20° 59' 14.81" 35° 00' 39.16" SW,SS, BS, OSL Riverbank Fines and sand

M16 21° 02' 36.45" 34° 52' 26.00" SS Riverbank. Not included in the study, destroyed during transportation.

Fines

M17 21° 03' 22.07" 34° 51' 51.87" SS Building area for irrigation pipes Fines

M18 21° 04' 01.70" 34° 51' 36.03" SS Sand/gravel pit Sand

M19 21° 02' 52.44" 34° 53' 15.43" SS Pond Fines

M20 21° 00' 22.90" 34° 56' 21.58" SW River

M21 20° 59' 07.66" 35° 00' 46.51" SS Riverbank Fines

M22 21° 01' 04.26" 35° 01' 39.83" SS Overflow levee Fines

M23 21° 01' 30.04" 35° 01' 56.28" SW River

M24 20° 59' 05.86" 35° 02' 06.07" SW River

M25 20° 58' 19.92" 35° 02' 29.47" BS Riverbank Fines and sand

M26 20° 56' 43.18" 35° 02' 52.58" SW M26a: Overflow area, M26b: River channel

M27 20° 56' 24.97" 35° 02' 9.92" SS. Most likely aeolian sediments

Riverbank. Not included in the study, irrelevant.

Sandy silt

M28 20° 56' 11.47" 35° 02' 46.28" SW, SS Riverbank Fines

M29 20° 56' 47.00" 35° 02' 50.89" SW, SS Riverbank Fines

M30 20° 59' 36.27" 35° 59' 55.42" SS Riverbank Fines

M31 21° 01' 37.88" 34° 54' 23.25" SS Riverbank Sand

M32 21° 07' 58.37" 34° 33' 55.15" SW, SS, Riverbank Sand

P1*** 21° 00' 22.96" 34° 56' 21.44" BS, OSL, 14C Riverbank Fines and sand

P2*** 20° 59' 14.82" 35° 00' 39.17" BS, OSL, 14C Riverbank Fines and sand

P3*** 20° 59' 06.71" 35° 02' 05.55" BS, OSL, 14C Riverbank Fines and sand

P6*** 21° 01' 24.04" 35° 04' 05.87" BS Transition upper-lower deltaic plane Fines and sand

P8*** 21° 01' 12.77" 34° 59' 35.22" BS Transition upper-lower deltaic plane Fines and sand

*SW: Surface water. SS: Surface sediments. BS: Buried sediments. MC: Mangrove cortex **Classified during field work. ***Massuanganhe et al. (2016a)

15

Figure 3. The tributary river channel in the Save River delta. Mangrove forest grows in parts of the delta and especially along the river channel. The picture is taken close to M5.

The described fieldwork was performed June 9-20, 2015, by the author and concerns M1-

M32. Four types of samples were collected; surface sediments, buried sediments, surface

water and mangrove cortex. Samples were titled with the same name as the site where they

were collected.

3.1 Siliceous microfossils

Samples for siliceous microfossil analysis were collected from surface sediments, buried

sediments, surface water and mangrove cortex.

Surface sediment samples were collected with a small spade from ground surfaces. Buried

sediments were sampled using the same technique, but collected from riverbanks (Figures 4

and 5). When surface water samples were collected, 1.5 liter plastic bottles were filled at

maximum 50 cm water depth. Samples were taken from boat or from the river bank. Bottles

were decanted after c. 12 h of sedimentation (Figure 6). Decanting was repeated every

second hour until c. 30 ml remained. Samples containing large amounts of sand were stirred

and decanted after 5 s of sedimentation. Remaining 30 ml of water were kept in tubes of 45

ml during transportation to Sweden. Two pH measurements were made with litmus in the

middle of the river channel at M1 and M10, both indicating neutral pH levels.

16

The outer most cortexes were scraped with a knife from living mangrove trees growing in

water. All scraping were made below the water surface (at the time of sampling).

Figure 4. A section from the river bank of the Save River with vertical layers of alluvial sediment with different grain sizes. The picture is taken close to M11. Surface and buried sediment samples were taken from similar sections along the river bank.

Figure 5. Parts of a section showing a fine grained layer at M9, which was sampled for diatom analysis. Sand with iron precipitation is present below and above.

17

Subsamples of 0.5-1.0 cm3 were extracted from surface and buried sediments and put into

100 ml beakers. Regarding samples from mangrove cortex, the outermost from the cortex

were scraped off and also put into 100 ml beakers. Surface water samples were decanted

after 2 hours of sedimentation and then poured into 100 ml beakers. 10 % HCl were added

to remove carbonates and organics were removed by boiling samples in 17-35 % H2O2 until

reaction terminated (Battarbee, 1986). Samples were then repeatedly decanted to remove

sand and clay particles using settling time times in water based on Stoke’s law. To dissolve

clay flocculates NH3 was added and the decanting procedure repeated until the liquid was

clear. Remaining water and fractions of silt-size were mounted in Naphrax® on microscope

slides to increase the refraction index.

Figure 6. Plastic bags containing surface and buried sediment samples. The 1.5 liter plastic bottles are samples collected from surface water. They were repeatedly decanted until c. 30 ml of water and sediments remained. Residuals were poured into plastic tubes of 45 ml and transported to Sweden.

Siliceous microfossils were analyzed under a Zeiss Axiophot light microscope using

immersion oil and X1008 magnification. Frustules were identified following Foged (1975),

Gasse (1986), Snoeijs (1993), Snoeijs & Vilbaste (1994), Snoeijs & Potapova (1995), Snoeijs &

Kasperovičienė (1996), Krammer & Lange-Bertalot (1986, 1988, 1991a, b, 2000), Metzeltin

(1998) and Witkowski et al. (2000). For practical reasons and available literature, new names

of certain species have not been applied. For example Synedra ulna and Biddulphia aurita

18

are at present named Ulnaria ulna and Odontella aurita, respectively (Lange-Bertalot &

Compére, 2001; Hoppenrath, 2004).

Eight groups based on salinity tolerance of diatom species were established; marine,

brackish, halophilic, indifferent, freshwater, aerophilic, unknown and extinct. Halophilic taxa

prefer increased salinities, which freshwater species do not. Indifferent taxa tolerate low

salinity levels, they can thus live in both fresh and brackish water. The group unknown

includes diatom frustules, which were not possible to identify because of breakage, chemical

dissolution or large amounts of mineral fractions covering the frustule. Characteristic/

commonly occurring species for a sample were based on frustule occurrences in relation to

other taxa.

Diatom assemblages within samples from surface sediments, surface water and mangrove

cortex are presented in pie charts on SPOT images of the investigated area. The groups

brackish and halophilic, indifferent and aerophilic were combined to explicate results. Based

on the same argument, the investigated area was divided into subareas 1, 2 and 3. Data for

the pie charts is presented in a geographical order perpendicular to the river, from east to

west (Appendix 1). M22 and M23 are not incorporated into the pie charts as they are not

located close to the present river channel. Samples where no frustules were found are not

visualized. Samples with low basic sums (<50 diatom frustules) were interpreted accordingly.

Diatom assemblages from buried sediment samples are presented as diagrams made in Tilia

1.7.16. P2/M14 is presented as percentage and P1, P3, P6, P8, M9 and M25 are presented as

counts since basic sums were too low. Diatom assemblage zones within P1, P3, P6 and P8

are modified from Massuanganhe et al. (2016a) to emphasize data important for the aim of

this study. In Massuanganhe et al. (2016a) zones are based on the lithological units while in

the present study they are defined according to diatom occurrences and ecologies (cf.

Appendices 2 and 3). The lithology is based on Troels-Smith (1955) classification of

sediments. Cluster analysis based on CONISS and eye matching was added into P2/M14 to

display zonation. Cluster analysis was not applied to diagrams with counts.

19

3.2 ESEM

Residuals from surface sediment samples M1-M4, M6, M10, from mangrove cortex samples

M1, M2, M5 and from surface water sample M1. Subsamples were paved with gold and

studied using ESEM (FEI, Quanta FEG 650) high vacuum. Diatom taxa particularly examined

to identify to species level were e.g. Diploneis interrupta, Opephora minuta, Luticola mutica,

Diploneis sp. and Cyclotella sp.

3.3 OSL

Two OSL-samples were collected at site M9. Opaque plastic tubes were driven into the sandy

layers. During the sampling procedure, black tarpaulin was used for light protection and

tubes were then covered with several layers of black tape (Figure 7). OSL-sample M9V was

collected vertically because of rising tidal water, which implied limited time for digging.

Approximately 1 kg of sediments was collected for dose rate measurement. Preparation

technique of luminescence samples is presented in Massuanganhe et al. (2016a). Sediment

for dose rate measurements for M9 and M9V was sent to VKTA, Laboratory for

Environmental and Radionuclide Analyses, Dresden, Germany.

Figure 7. The vertical OSL samples from M9. Black tarpaulin was used for light protection during collection. The plastic sample tube was covered with black tape to ensure tight coverage.

4. Result and interpretation

Four categories of material have been collected; surface water (20), surface sediments (21),

mangrove cortex (5) and buried sediments (16). The latter category has partly been collected

by Elidio Massuanganhe and analyzed by Annika Berntsson and the author of this study

20

(Massuanganhe et al., 2016a). During analysis 63 diatom genera and 258 species were

identified (Appendix 3). Phyotoliths, sponge spiculae and chrysophyte cysts were identified

but not counted as they were not relevant for the objectives of this investigation. Most

common species are Nitzschia granulata, N. littoralis, Hantzschia distinctepunctata,

Cyclotella sp., Thalassiosira eccentrica, Diploneis sp. and D. interrupta. (Appendices 3 and 6).

Numbers of brackish and marine diatom species are overall higher in samples from surface

water, surface sediment and cortex than in buried sediments, exemplified by Amphora

ventricosa, Opephora pacifica and Navicula alpha.

Diatom assemblages in surface sediments, surface water and mangrove cortex are

presented as pie charts overlying geographical maps to show the salinity gradient in the

lower Save River (Figures 8, 9, 10 and Appendix 1). Identified diatoms are grouped according

to associated ecology and presented as percentages. The basic sums of identified frustules in

each sample vary between 0 and 353.5 (Figures 8C, 9D and 10B). Differences in diatom

assemblages indicate a spatial variation in salinity. Marine and brackish species are generally

decreasing up-streams while indifferent and freshwater taxa are increasing. Diatoms can

thus indicate a latitudinal salinity gradient in the lower Save River. Brackish taxa are present

in nearly all samples, which indicate influences of tidal water up-stream.

4.1 Surface water samples

20 surface water samples were collected (Figure 8 A and B). No surface water samples were

collected in Subarea 3. In Subarea 1, brackish and halophilic taxa are dominant (Figure 8 A).

The number of indifferent and aerophilic taxa in the diagram at site M1 is relatively low as

the basic sum is only eight and should be interpreted accordingly (Figure 8 B). The sample at

site M11 shows a high occurrence of marine species in relation to samples closer to the

ocean.

Samples from Subarea 2 show a significantly higher occurrence of brackish and halophilic

taxa than in Subarea 1 (Figure 8 B). Low numbers of marine diatoms are identified in the

sample at site M13. The occurrence of indifferent and aerophilic taxa starts to increase at

site M24 and continuous in samples at site M20 and M32. The occurrence of freshwater

diatoms is, however, limited in water samples throughout the delta and the river channel.

21

4.2 Surface sediment samples

21 surface sediment samples were collected (Figure 9 A, B and C). Brackish taxa are

dominating most of the samples from Subarea 1 (Figure 9 A). M11 contain a relatively high

number of freshwater species. In sample M25 marine taxa occur in the same proportions as

in Subarea 1 (Figure 9 B). In the other two samples visualized in Subarea 2 (M21 and M30)

the indifferent and aerophilic taxa increase and marine species decrease. The brackish taxa

are still dominating. Amount of freshwater species are significantly higher in M31 and M32,

Subarea 3, (Figure 9 C), however, they do not occur in M15, M17 and M18. Brackish taxa are

highly represented in M15 and M17. Note the low basic sums in samples M15, M17 and M18

(Figure 9C).

4.3 Mangrove cortex samples

During fieldwork five mangrove cortex samples were collected. Samples from mangrove

cortex were collected within Subarea 1 at sites M1-M5 (Figure 10), i.e. in the delta front. The

diatom communities indicate mostly brackish water conditions. In M1 and M3 there is a

marine signal, however, the basic sum in M1 is too low to be valid (Figure 10). The diatom

assemblage in M5 indicates some influence of freshwater since frustules of Cymbella spp are

present.

22

Figure 8 A. Identified diatom frustules from surface water samples. Counts are grouped according to optimal salinity and

presented as percentages in pie charts. Colors in the pie charts represent different salinity levels and are explained in the

legend. The overview map in the lower right corner display the geographical position of subarea 1.

23

Figure 8 B. Counted diatoms from surface water samples within Subarea 2. The table below the map display basic sums for each sample. See Figure 8 A for additional details.

M3

2

26

7

M2

9

12

0

M2

8

19

4.5

M2

6b

35

3.5

M2

6a

17

7

M2

4

94

M2

0

39

.5

M1

4

53

M1

3

91

M12

229

M11

136

M10

49

M 9

33

M6

97.5

M5

72.5

M4

b

37

M4a

32.5

M3

44

M2

43.5

M1

8

Sam

ple

Bas

ic

sum

24

Figure 9 A. Diatom counts from surface sediment samples displayed as percentages. Counts are grouped according to

optimal salinity. The colors within the pie charts represent different salinities and are explained in the legend in Figure 8A.

Overview map in the lower right corner show the geographical position of Subarea

1

25

.

Figure 9 B. Diatom counts from surface sediment samples within Subarea 2. See Figure 9 A for further details.

26

Figure 9 C. Diatom frustules from surface sediment samples within Subarea 3. See Figure 9 A for further details. The table below the figure show basic sums for the samples.

M3

2

7.5

M1

8

11

M1

7

1

M1

5

14

.5

M3

1

36

M3

0

20

5

M2

1

13

8

M2

5

13

4

M1

2b

20

2

M12

a

208.

5

M11

33

M29

110

M28

63.5

M10

162.

5

M6

369

M8

14

M4

42

M3

70

M7

91

M2

204.

5

M1

32

Sam

ple

Bas

ic

sum

27

Figure 10. Identified diatoms from mangrove cortex. Pie charts contain identified frustules counted as percentages and represented with different colors depending on their optimal salinity. Legend of the colors are available in Figure 8 A. The table below the map show basic sums for the samples. Geographical position of Subarea 1 is showed in the overview map in the lower right corner.

M5

359

M4

75

M3

54

M2

45

M1

4.5

Sam

ple

Bas

ic

Sum

28

4.4 Buried sediments

Buried sediment samples were collected at P1, P2/M14, P3, P6, P8, M9, and M25 and

presented in seven Tilia diagrams (Figures 11-17). Detailed lithologic information of P1, P3,

P6 and P8 is modified from Massuanganhe et al. (2016a). 16 samples were collected at M-

sites and 126 samples at P-sites. Samples P2 and M14 are merged as their geographical

location coincide. The lithology at all sites shows a clay layer bracketed by units consisting of

sand and/or silt.

The diagram from P1 is divided into two zones, however diatom frustules only occur in zone

1) (Figure 11). Basic sums of diatoms are high in the lowest part of the core, c. 620-560 cm

depth. In zone 1 variations between the ecological groups are minor. The frustules counted

represent mainly brackish (e.g. Diploneis interrupta and D. pseudovalis) and indifferent

conditions (e.g. Amphora copulata), however, marine (Nitzschia granulata) and freshwater

(e.g. Fragilaria ulna) diatoms co-occur. Two samples were collected for radiocarbon dating

suggesting ages of 3216-2980 cal. yrs BP (Poz-67397) at c. 570 cm depth and 1072-956 cal.

yrs BP (Poz-60019) at c. 320 cm depth (Figure 11 and Table 2). At c. 350 cm depth a sample

for OSL dating was collected, indicating an age of 1300±160 years (Figure 11 and Table 3).

In P3, zone 1 identified diatom frustules are few, but those occurring represent marine and

brackish conditions (Figure 12). Zone 2 contain a higher number of diatoms and the marine

and brackish signal is more clear and represented by e.g. Paralia sulcata and Diploneis

interrupta. In zone 3 the brackish and marine signal remains strong, additionally

characterized by Nitzschia granulata and Hyalodiscus sp. Aerophilic species (e.g. Hantzschia

amphioxys) are highly occurring in zone 4, however, brackish, indifferent and freshwater

taxa co-occur, mostly represented by Diploneis interrupta, Fragilaria brevistrata and Eunotia

spp. The OSL date at c. 370 cm depth indicates an age of 210±20 years (Figure 12 and Table

3).

29

Figure 11. Diatom diagram from P1. Sums of identified diatom frustules are displayed as counts. DAZ (diatom assemblage zones) are constructed based on frustule occurrences. The chronology comprises both OSL and radiocarbon dates. OSL is marked with ± and radiocarbon as a time interval.

240

290

340

390

440

490

540

590

640D

epth

(cm

)

13

00

±1

60

10

72

-95

6

32

16

-29

80C

hron

olog

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Nitz

schi

a gr

anul

ata

20

40

Dip

lone

is in

terr

upta

20

40

60

80

Dip

lone

is p

sued

oval

is

20

Han

tzsc

hia

dist

inct

epun

ctat

a

20

Hya

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0

Nitz

schi

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20

40

Am

phor

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taE

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emia

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ata

Rho

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a

Rho

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ica

20

Fragi

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uln

a

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Han

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s

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00

00

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00

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10

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40

33

60

28

55

32

97

15

23

04

Bas

ic s

um

20

Mar

ine

taxa

50

100

150

Bra

ckis

h ta

xa

Hal

ophi

lic ta

xa 20

40

60

80

100

Indi

ffere

nt ta

xa

20

40

Fresh

wat

er ta

xa

Aer

ophi

lic ta

xa

20

Unk

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n ta

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AZ

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Ma

rine

ta

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h ta

xaIn

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ate

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5-2

01

6

Lith

olog

y

Silt

Sa

nd

Cla

yS

ilty

sa

nd

Silt

y cla

y

30

Figure 12. Diatom diagram from P3. Sums of identified diatom frustules are displayed as counts. DAZ (diatom assemblage zones) is constructed based on frustule occurrences. One OSL date is visible in the chronology.

The occurrence of diatoms is relatively low in samples from P6 and merely 11 of 29 samples

contain frustules (Figure 13). In zone 1 there is a brackish-marine signal dominated by mainly

Diploneis interrupta and Terpsinoë americana. Zone 2 indicates the same signal as zone 1,

however, the occurrence of frustules is higher. Aerophilic species is most common in zone 3.

Significant taxa are Navicula mutica and Pinnularia borealis.

70

120

170

220

270

320

370D

epth

(cm

)

21

0±

20C

hron

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y

Dip

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is c

affra

20

Nitz

schi

a gr

anul

ata

20

Par

alia

sul

cata

20

Dip

lone

is in

terr

upta

Dip

lone

is p

seud

oval

is

Han

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inct

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20

Hya

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scus

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ria b

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ta

Eun

otia

spp 2

04

0

Han

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Nav

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Nav

icul

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18

33 2

17

37

65 4 6 3

52

48

86

60

11

Bas

ic s

um

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Mar

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taxa

20

40

Bra

ckis

h ta

xa

Hal

ophi

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Indi

ffere

nt ta

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Fresh

wat

er ta

xa 20

40

Aer

ophi

lic ta

xaU

nkno

wn

taxa

DAZ

4 3 2 1

Ma

rine

ta

xaB

rackis

h ta

xaIn

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rent ta

xaF

reshw

ate

r ta

xa Ae

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Modifi

ed fro

m B

ern

tsson 2

015-2

016

Lith

olog

y

Sa

nd

Silt

y cla

yS

ilt

31

Figure 13. Diatom diagram from P6. Sums of identified diatom frustules are displayed as counts. DAZ (diatom assemblage zones) is constructed based on frustule occurrences.

In P8 the occurrence of diatoms is relatively low (Figure 14). Only five out of 23 analyzed

samples contain frustules. Zone 1 is characterized by a brackish signal represented by

Hyalodiscus sp. In zone 2 minor occurrences of brackish and marine taxa are present, e.g.

Diploneis caffra and Diploneis interrupta. Zone 3 predominately contains aerophilic species

(Hantzschia amphioxys, Navicula mutica and Pinnularia borealis).

0

50

100

150

200

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300

350

400D

epth

(cm

)

20

Paral

ia s

ulca

ta

Dip

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is in

terr

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Hya

lodi

scus

sp.

Nitz

schi

a co

ccon

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Terps

inoë

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eric

ana

Han

tzsc

hia

amph

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Nav

icul

a go

eppe

rtian

a

Nav

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a m

utic

a

Pinnu

laria

bor

ealis

19 0 0 1 0 0 1 0 0 0 0 0

28 2

23

21

3 0 6

11

14 0 0 0 0 0 0 0 0Bas

ic s

um

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Mar

ine

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Brack

ish

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Indi

ffere

nt ta

xa

20

Aerop

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taxa

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xa

DA

Z

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Marine t

axa

Bra

ckis

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axa

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Mo

difie

d f

rom

Bern

tsso

n 2

015

-201

6

Lith

olog

y

Silt

Cla

yS

and

32

Figure 14. Diatom diagram from P8. Sums of identified diatom frustules are displayed as counts. DAZ (diatom assemblage zones) is constructed based on frustule occurrences.

Diatom analyses from M9 were undertaken on samples from silty sand and two clay layers

(Figure 15). The basic sums of diatoms are relatively low. In zone 1 there is a marine-brackish

signal. Dominating taxa are Coscinodiscus asteromphalus, Nitzschia granulata, Opephora

minuta, Paralia sulcata, Cyclotella sp. and Diploneis sp. In zone 2 the occurrences of diatom

frustules are low. Identified taxa indicate marine and brackish water conditions. Zone 3 is

also dominated by marine and brackish species. Most common taxa are Nitzschia granulata,

Paralia sulcata, Diploneis interrupta and Nitzschia littoralis. Below 320 cm depth a sand layer

of unknown thickness is present, followed by a clay layer 220-320 cm depths. Above the clay,

silty sand is present at 220-195 cm depth. Between 195 and 145 cm depth sand follows. A

relatively thin layer of clay is present above, at 155-145 cm depth. From 145 cm depth to the

ground surface a massive layer of sand occurs. Two samples for OSL-dating were collected at

330 and 180 cm depth (Figure 15 and Table 3). These indicate ages of 890 ± 100 yrs and 920

± 90 yrs, respectively. Accordingly, the ages are approximately equal, despite difference in

depth.

0

20

40

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80

100

120

140

160

180

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220

240D

epth

(cm

)

Dip

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is c

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ata

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ia s

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Dip

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is in

terr

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20

Hya

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Terps

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eric

ana

20

Han

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Nav

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Nav

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a m

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Nitz

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Basic

sum M

arin

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rnts

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01

5-2

01

6

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olog

y

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Cla

yS

and

33

Figure 15. Diatom diagram from M9. Sums of identified diatom frustules are displayed as counts. DAZ (diatom assemblage zones) is constructed based on frustule occurrences. Two OSL dates are presented.

0

50

100

150

200

250

300

350D

epth

(cm

)

89

0±1

00

92

0±9

0Chr

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20

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Cosc

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97 1

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Basic

sum

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40

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20

40

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Brack

ish

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xa

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xa

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own

taxa

Extin

ct ta

xa DA

Z

3 2 1

Ma

rine

taxa

Bra

ckis

h ta

xa

Ma

rie

Chri

stia

nsso

n 2

01

6

Lith

olog

y

Sand

Cla

yS

ilty s

and

34

The diatom diagram from P2/M14 is constructed based on samples collected by the author

combined with published data (Figure 16). Brackish diatoms dominate in zone 1 and are

represented by e.g. Actinoptychus sp., Diploneis interrupta and D. pseudovalis. Occurrences

of the freshwater taxon Gyrosigma obtusatum are also present. In zone 2, marine taxa e.g.

Paralia sulcata and Nitzschia granulata are present. There is a clear brackish signal indicated

by Diploneis interrupta, D. pseudovalis and Hantzschia distinctepunctata. In zone 3 brackish

taxa dominate, characterized by mainly Diploneis interrupta. In zone 4 the brackish signal

decreases in comparison to zone 3 and indifferent species increase. Diploneis interrupta is

still the dominant brackish taxon and Amphora copulata characterizes the indifferent

species. In zone 5 brackish taxa increase from zone 4 with high occurrences of Diploneis

interrupta. At this site four radiocarbon dates and two OSL dates were performed. The result

suggests ages which are not in chronological order in relation to the depth. The youngest

radiocarbon date occur at 410 cm depth and indicate an age of 800-682 cal. yrs BP (Poz-

53659). The two other radiocarbon dates stratigraphically above show ages 1570-1405 cal.

yrs BP (Poz-53658) (310 cm depth) and 920-766 cal. yrs BP (Poz-53657) (270 cm depth)

respectively (Figure 16 and Table 2). The OSL dates are measured at 500 and 200 cm depths,

both suggesting similar ages of 250±30 yrs and 230±20 yrs (Figure 16 and Table 3). The

lithology at P2/M14 comprises sand in the lower most unit, followed by clay up to 220 cm

depth. A massive sand layer is then present up to the surface, with two interlayers of sandy

silt at 220-195 and 155-145 cm depth. A detailed lithology is available in Massuanganhe et

al. (2016a).

35

Figure 16. Diatom diagram from P2/M14. Data from the two sites are combined as the samples were collected at the same geographical location. Diatom sums of identified diatom frustules are displayed as percentages. DAZ (diatom assemblage zones) is constructed based on cluster analysis constructed from CONISS combined with eye matching. The chronology comprises both OSL and radiocarbon dates. OSL is marked with ± and radiocarbon with a time interval.

200

250

300

350

400

450

500

550D

epth

(cm

)

920-7

66

230±20

250±30

1570-1

405

800-6

82

2105-1

995C

hron

olgy

20

Nitz

schi

a gr

anul

ata

Paral

ia s

ulca

ta

20

Actin

opty

chus

sp.

20

40

60

80

Dip

lone

is in

terru

pta

20

40

Dip

lone

is p

seud

oval

is 20

Han

tzsc

hia

dist

inct

epun

ctat

a

20

Nitz

schi

a lit

tora

lis

20

Cyc

lote

lla m

eneg

hini

ana

20

Amph

ora

copu

lata

20

Nav

icul

a cu

spid

ata

20

Aulac

osei

ra g

ranu

lata

20

Gyr

osig

ma

obtu

satu

m

61

86

99

10

6

85

10

0

74

66

79

54

11

2

85

80

81

89

68

59

19

7

83

70

30

3

20

0

20

79

71

75

75

31

71

0Bas

ic s

um

20

Mar

ine

taxa

20

40

60

80

100

Brack

ish

taxa

20

Hal

ophi

lic ta

xa 20

40

Indi

ffere

nt ta

xa

20

Fres

hwat

er ta

xa

20

Aerop

hilic

taxa

20

Unk

now

n ta

xa DA

Z

5 4 3 2 1

Marine taxa

Bra

cki

sh taxa

Halo

phili

c taxa Indiff

ere

nt ta

xaF

reshw

ate

r ta

xa

Be

rnts

so

n &

Ch

ris

tia

ns

so

n 2

01

5-2

01

6

24

68

10

To

tal s

um

of s

qu

are

s

CO

NIS

S

Lith

olog

y

Sand

Cla

yS

ilty

sand

36

In the diagram from M25 the diatom analysis indicates merely taxa which are associated

with marine and brackish conditions (Figure 17). The signal is distinctive throughout the

section. In zone 1 marine species dominate, e.g. Actinoptychus splendens, Paralia sulcata and

Nitzschia granulata. Zone 2 is characterized by brackish taxa represented by mainly

Cyclotella sp. In zone 3, the most commonly occurring diatom taxa are marine represented

by e.g. Actinoptychus splendens and Nitzschia granulata. M25 consists of a massive layer of

clay.

Figure 17. Diatom diagram from M25. Sums of identified diatom frustules are displayed as counts. DAZ (diatom assemblage zones) is constructed based on frustule occurrences.

0

50

100

150

200

250

300D

epth

(cm

)

20

Actin

opty

chus

spl

ende

ns

20

Cos

cino

disc

us a

ster

omph

alus

Cyc

lote

lla s

tylo

rum

Dip

lone

is s

mith

ii

Nav

icul

a al

pha

Nav

icul

a ya

rrens

is

20

Nitz

schi

a gr

anul

ata 2

0

Paral

ia s

ulca

ta 20

Thala

ssio

sira

ecc

entri

ca

Cyc

lote

lla c

rass

a

50

10

01

50

20

0

Cyl

otel

la s

p.

Dip

lone

is in

terr

upta

Dip

lone

is s

p.

14

4

24

2

10

5 5

Basic

sum

50

10

01

50

Mar

ine

taxa

50

10

01

50

20

0

Brack

ish

taxa

Indi

ffere

nt ta

xa

Fresh

wat

er ta

xa

20

Unk

now

n ta

xa DA

Z3 2 1

Ma

rine

ta

xa

Bra

ckis

h t

axa

Marie

Christiansso

n 2

01

6

Lith

olog

y

37

Table 2. Details from radiocarbon dates (Massuanganhe et al.2016a).

Sample/Site Depth (cm) Type of material Lab nr. Age BP 14C Cal. yrs BP 95.4% confidence

P1 320 Bulk sediments Poz-60019 1165±30 1072-956 (95.4%)

P1 570 Plant remains Poz-67397 2995±30 3216-2980 (95.4%)

P2/M14 270 Bulk sediments Poz-53657 965±30 920-766 (95.4%)

P2/M14 310 Bulk sediments Poz-53658 1640±35 1570-1405 (95.4%)

P2/M14 410 Roots Poz-53659 890±30 800-682 (95.4%)

P2/M14 470-480 Roots Poz-53660 2110±25 2145-2129 (2.6%)

2105-1995 (88.5%)

1960-1934 (4.2%)

Table 3. OSL dates and measurements details. Data from P2/M14 and P3 are earlier published in Massuanganhe et al. (2016a). M9 was sampled horizontally into the sediment and M9V were

collected vertically.

1 Estimated water content relative to the dry sample weight 2 Number of aliquots (2 mm) passing measurement recycling criteria (≤10%). 3 Overdispersion (Galbraith et al., 1999). 4 Central Age Model (CAM) (Galbraith et al., 1999). 5 Minimal Age Model (MAM) (Galbraith et al., 1999) at 10% overdispersion (sample P3 at 7.2%) *Massuanganhe et al. (2016a)

Site Surface

altitude

Sample

depth

Water

content1

n2,4 OD3,4 238U 226Ra 232Th 40K CAM4 De CAM4 age MAM5 De MAM5 dose

rate

MAM5 age

(m

a.s.l.)

(cm) (%) (%) (Bq kg-1) (Bq kg-1) (Bq kg-1) (Bq kg-1) (Gy) (a) (Gy) (Gy ka-1) (a)

P1* 11 36 10 ± 5 58 37.9 32.0 ± 2.0 31.4 ± 2.0 62.0 ± 4.0 865.0 ± 71.0 6.42 ± 0.32 1590 ± 180 5.26 ± 0.4 4.05 ± 0.49 1300 ± 160

P2*/M14 6 200 10 ± 5 40 44.6 25.4 ± 1.6 25.4 ± 1.6 51.0 ± 4.0 943.0 ± 77.0 1.17 ± 0.08 290 ± 40 0.94 ± 0.03 4.09±0.35 230±20

P2*/M14 6 500 15 ± 5 48 22.3 28.0 ± 5.0 18.6 ± 1.3 54.0±3.0 841.0±69.0 0.84±0.03 250±30 0.79±0.01 3.43±0.30 230±20

P3* 5 370 15 ± 5 45 7.2 9.0 ± 3.0 7.2 ± 0.6 14.3 ± 1.0 842.0 ± 69.0 0.55 ± 0.01 210 ± 20 0.55 ± 0.02 2.62 ± 0.25 210 ± 20

M9 4 180 15 ± 5 41 15.4 6.5 ± 2.3 4.8 ± 0.5 8.8 ± 0.9 933.0 ± 76.0 2.61 ± 0.07 930 ± 100 2.56 ± 0.05 2.78 ± 0.27 920 ± 90

M9V 4 330 15 ± 5 39 26.7 17.0 ± 2.8 17.0 ± 1.1 61.0 ± 4.0 470.0 ± 40.0 2.66 ± 0.12 1050 ± 110 2.26 ± 0.12 2.54 ± 0.28 890 ± 100

38

4.5 Taxonomic remarks

Diatom frustules, which were not possible to identify to species level because of

fragmentation, chemical corrosion and/or overlying of mineral particles have been labeled

“spp”. Frustules appearing as similar, but not possible to identify to species level are

categorized as “sp.”. Two diatom genera, which were not possible to identify to species

level, were selected for comprehensive identifications as they occurred in large numbers

both in sediments and water samples. These were identified to genus level as Cyclotella and

Diploneis (Tables 4 and 5). Cyclotella sp. has been compared with five taxa showing similar

morphologies in an attempt to identify to species level (Table 4). None of them corresponds

in detail, which makes it difficult to identify Cyclotella sp. Species C. stylorum and C. litoralis

show most similarities, however, there are significant differences in size and character of the

central and marginal fultoportulae. Cyclotella sp. has a higher quantity of central

fultoportulae and a different pattern of the marginal fultoportulae. Cyclotella sp. was

frequently occurring in samples geographically located east of M30 (Figure 1). Other species

identified in samples east of M30 are generally brackish and marine. Based on the

geographical distribution of Cyclotella sp. and the ecology of related taxa the unidentified

species was interpreted as being associated with brackish conditions.

The morphology of the unidentified species Diploneis sp. is most similar to Diploneis

pseudovalis (Table 5). Size and areolae structure are, however, somewhat different. The

valve size of Diploneis sp. is significant smaller than all compared species, which may be

related to differences during the life cycle or may be an indication of limiting environmental

conditions. Frustules of Diploneis sp. co-occur with Cyclotella sp., thus, the ecology for

Diploneis sp. was also associated with brackish environment based on the same arguments

as with Cyclotella sp. These two species may be identified as species not earlier described.

39

Table 4. Comparison between Cyclotella sp. and five described species of the Cyclotella genera with similar morphological structures. References to each species are presented below. C. stylorum and C. litoralis most related, but size and character of the central and marginal fultoportulae are not corresponding. Cyclotella sp. is interpreted to be associated with brackish conditions as frustules were frequently identified east of M30, which contain mostly brackish and marine taxa. Cyclotella sp. may not have been described earlier. ESEM micrographs of Cyclotella sp. are presented in Appendix 4.

Species Valve diameter

(µm)

Marginal striae/10

µm

Character of the central

nodule

Character of the central

fultoportulae

Character of the marginal

fultoportulae

Rimoportula Ecology

Cyclotella sp. (present study) n=10

10-27 8-11 Circular, undulate and

colliculate

14-36. 3 satellite pores (concave side). Scattered

in the central nodule

On every 2nd and 3rd

interstriae

Single, sessile, radially

oriented and taper

Brackish

C. striata1,2,3, 4

10-67 8-10 Undulate, colliculate

None On every 3rd or 4th interstriae

Single, lateral Brackish

C. idahica3,5

6.5-48 7-10, areolae

Transversal undulating,

oval to elongate, irregular arranged areolae

Present, 2 or 4 satellite pores on the convex valve, 3 satellite pores on the concave

valve

Located in chambers on the concave valve, 3 satellite pores

Single, radial Freshwater

C. stylorum2,3,6,7

25-80 8-10 Undulate, colliculate

6-12, located in a semicircle on the

elevated undulation

In marginal chambers, in

pairs or triplets on interstriae

Single, radial, in a chamber

Marine

C. litoralis3,7,8,10, 11

10-63 8-12 Undulate, colliculate

2-20, occasionally in

pairs, located in a semicircle on

the elevated undulation

On every 2nd

interstiae Single, radial,

sessile Brackish

C. baltica2,8,9

11-45 9-13 Slightly undulate, colliculate

2-9, 3 satellite pores located in a semicircle on

the elevated undulation

On every 2nd to 3rd interstriae

Single, sessile, slit-like opening

Brackish

1 Håkansson (1996), 2 Håkansson (2002), 3 Krammer & Lange Bertalot et al. (1991a), 4 Round et al. (1990), 5Kociolek &

Khursevich (2013), 6Foged (1975), 7Lange & Syvertsen (1989), 8Park et al. (2013), 9Prasad & Nienow (2006), 10Marshall

(1978), 11Lehmkuhl et al. (2010).

40

Table 5. Comparison between Diploneis sp. and five other species of the genera Diploneis with similar morphological structures. References to each species are presented below. Diploneis sp. is most similar to D. pseudovalis, however, size and areolae structures are different. Note that the valve size of Diploneis sp. is significantly smaller than compared species. This may be related to natural valve size variations during the life cycle, or be an indication of limiting environmental conditions. Diploneis sp. is interpreted to be brackish as identified frustules mainly co-occur with brackish species. Diploneis sp. may be considered as a species not earlier described. ESEM micrographs of Diploneis sp. are presented in Appendix 5.

1 Krammer & Lange-Bertalot (1986), 2Witkowski (2000), 3Hemphill-Haley & Lewis (1993), 4Foged (1975), 5Jovanovska et al. (2013)

Species Valve length (µm)

Valve width

µm

Transapical striae/10

µm

Transapical striae structure

Areolae structure

Character of the raphe

Character of the sternum

Valve outline

Ecology

Diploneis sp. (present study)

n=10

8.5-20 5-11 9-14 Slightly radiate near raphe

ends, one row of areolae

between raphe and apical

striae

Systematic, biseriate between costae,

arranged in quincunx

Slightly recurved at

proximal raphe slits and at the raphe ends

Transapical, elliptic at central nodule

Elongate-elliptic and

ends rounded

Brackish

D. pseudovalis1,2,3

16-31 9-14 8-12 Slightly radiate near raphe

ends, one row of areolae

between raphe and apical

striae

Biseriate between costae, rarely

arranged in quincunx

Slightly recurved at

proximal raphe slits

Transapical, rounded shape at central nodule

Elongate-elliptic and

ends rounded

Brackish

D. ovalis1,3

20-100 10-35 10-19 Slightly radiate near raphe

ends, one row of areolae

between raphe and apical

striae

Uniseriate between

transapical costae

Slightly recurved at

proximal raphe slits

Large oval central nodule

Wide-elliptic and

ends rounded

Indifferent

D. vetusa5

15-23 9-12.5

10-12 Slightly radiate near raphe

ends, areolae, and two rows of areolae at

the longitudinal canal

Biseriate, cribra

Slightly recurved at

proximal raphe slits

and significant

recurved at raphe ends

Transapical, elliptic

around the central nodule

Elliptic and ends

rounded

Indifferent

D. subovalis1,3

10-50 8-20 10-12 Radiate, an isolated row of areolae along longitudinal

canals and two rows of areolae

at the longitudinal

canal

Biseriate, arranged in

quincunx

Slightly broad

Large oval central nodule

Elliptical to linear-

elliptic and ends

rounded

Freshwater

D. smithii1,3,4

12-200 6.5-75

5-15 Radiate, longitudinal

canals broader in the middle

Biseriate, arranged in

quincunx

Broader at sternum

Varying size, round-square to elliptic at

central nodule

Wide-elliptic, linear-elliptic,

rhombic-elliptic and

ends rounded

Marine

41

5. Discussion

The discussion will mainly focus on taxonomic remarks, the salinity gradient and taphonomy.

It is generally suggested that the diatom assemblages within the lower Save River are

affected by several taphonomic processes. These may further aggravate the interpretation

of salinity levels, based on diatom analysis.

5.1 Taxonomy

In the present investigation two unidentified taxa of the genera Cyclotella and Diploneis

were noted and compared with earlier described species (Tables 4 and 5). Since frustule

characteristics did not agree in detail they are suggested to represent not earlier described

taxa. For example, diameter and length were generally smaller. Caution has to be taken,

however, since a limited number of frustules were encountered. Further analyses on

additional frustules using SEM should be beneficial and is also required to establish new

species with greater certainty.

Occurrences of unusually small diatoms, in relation to descriptions in floras, are especially

high in water samples and surface sediments. These are exemplified by Thalassiosira

eccentrica, Th. oestrupii, Diploneis interrupta, Diploneis sp., Luticola mutica and L. mutica v.

undulata. Size differences within a species community are commonly known as the size

reduction series (Hense & Beckmann, 2015; Falkowski & Knoll, 2007; Mann & Droop, 1996),

or caused by environmental factors (Finkel et al., 2009).

Considering all types of samples Diploneis interrupta is one of the most common taxon

(Appendices 3 and 6). Reference literature is not consistent regarding ecological preferences

for this species. Commonly, the taxon is associated with brackish water conditions (e.g. Zong

& Horton, 1998; Sandgren et al., 1999; Zalat, 2000; Zalat & Vildary, 2007). Vos & de Wolf

(1993:2) and Espinosa (2006) suggested a preference for brackish water and aerophilic

conditions. Earlier Vos & de Wolf (1988) stated that the species lived only in aerophilic

environments. D. interrupta occur together with other taxa representing various salinities.

Therefore, optimal salinity conditions for D. interrupta cannot be determined based on

geographical location and associated diatom taxa. Normally, these factors may act as guides

in dynamic environments such as deltas (Håkansson, 1996). As most of the literature refers

42

to the species as brackish, D. interrupta is in this investigation considered to be associated

with brackish conditions. Frequent occurrences of D. interrupta are also observed in the

material analyzed in Massuanganhe et al. (2016a). This species is heavily silicified and

therefore resistant to physical breakage and chemical dissolution (Furnas, 1990; Round et

al., 1990; Martin-Jézéquel et al., 2000). As this taxon has higher potential for surviving and

being well preserved under dynamic conditions there is a risk for over-representation. Thus,

interpretations based on stratigraphical and/or geographical distributions of D. interrupta

should be made with caution. In this study, observations of frustules were made up-stream

within the river channel (M32), both in surface sediments and surface water samples. This is

the single brackish water taxon in these samples representing 67 % and 2 % of taxa

identified. Note that the basic sum for diatoms observed in the surface sediment samples is

only 7.5 frustules. The surface water sample contained abundant diatoms resulting in a basic

sum of 267. The frustules identified could possibly have been brought by canoes and/or

birds (cf. Rothlisberger et al., 2010; Kilroy & Unwin, 2011), which could explain the

improbable geographical location. Some D. interrupta could theoretically live at M32 as high

evaporation may cause periods of increased salinity. It is, however, more likely that D.

interrupta is tolerant to a wide range of salinity, which previous investigations mentioned

above suggest (e.g. Vos & de Wolf, 1988; Vos & de Wolf, 1993:2; Zong & Horton, 1998;

Sandgren et al., 1999; Zalat, 2000; Espinosa, 2006; Zalat & Vildary, 2007).

5.2 Salinity gradient

The relationship between surface salinity gradients and diatom assemblages have been

studied in earlier investigations, e.g. John (1987), Bloom et al. (2003) and Jiang (1996), but

there is a lack of investigations from the east African coastal zone and deltaic environments.

Pie charts in Figures 8 A, 9 A and 10 A present the interpreted salinity based on identified

diatom species in samples from surface sediments, surface water and cortex within Subarea

1. The charts from surface sediment samples display a low occurrence of marine taxa in

relation to samples from surface water (Figures 9 A and 8 A). In samples from surface

sediments, the relation brackish/marine frustules is c.3.0. The low occurrence of marine

species may indicate a strong influence by the Save River also near the delta front. The

relation brackish/marine frustules for surface water samples is c.1.0 (Figure 8 A). This

43

number is much lower, despite sample collections from Subarea 1. It is, however, notable

that diatom communities in surface sediments and surface water samples consist of both

autochthonous and allochthonous diatoms. Therefore, these samples may not represent

salinity conditions at the sampled sites.

Diatoms scraped from mangrove cortex are likely of autochthonous origin, consisting almost

exclusively of benthic taxa (Figure 10 and Appendix 3). Those few planktonic species

identified can have been captured by mistake during the sampling procedure since scraping

was done beneath the water surface. Vos and de Wolf (1993:1) support the suggestion of

benthic diatoms being autochthonous. The relation between brackish and marine frustules

in the cortex samples is c.1.1. Since the relation in surface water samples is comparable

(c.1.0), it is suggested that those samples reflect salinity water conditions within Subarea 1.

Diatom analysis of surface sediment samples regarding salinity may underestimate prevalent

conditions within Subarea 1, due to influences by various taphonomic processes, and should

thus be interpreted with caution. This statement is supported by Hutchinson et al. (1995)

who identified inconsistences between modern and fossil diatom assemblages in the Fraser

River delta, Canada, probably caused by taphonomic processes. Because of presence of

these extensive taphonomic processes within the investigated area, diatom analysis on

sediments in paleoenvironmental studies is recommended to be interpreted with caution.

Further investigations on sediments should be conducted before results can be interpreted

as reliable.

Both the surface water sample and surface sediment at M11 show, in relation to its

geographical location, an unexpected distribution of diatom taxa (Figures 8 A and 9 A). In the

surface sediments diatoms preferring freshwater conditions are abundant representing c. 22

% (basic sum 33). The surface water sample shows a relatively high proportion of marine

taxa in comparison to nearby sites (c. 84%, basic sum 136). As M11 is relatively close to the

ocean a high abundance of marine taxa is anticipated as compared to high occurrences of

freshwater species. Therefore, frustules representing freshwater conditions are suggested to

be of allochthonous origin and thus not representative of the salinity at M11. The sample

from surface sediments has a high proportion of sand, which is in interpreted to characterize

fluvial conditions. Based on the above discussion it is suggested that the area around M11

44

(approximately 10 km upstream the delta front) may represent the transition from strong

ocean water influences to more freshwater, i.e. fluvial, conditions, at the time of sampling.

This is supported by the mangrove distribution, which was present from the delta front to

approximately M13 (c. 1.1 km upstream from M11).

5.3 Taphonomy Discussions in this section are based on diatom distributions in samples collected by the

author and Elidio Massuanganhe for his doctoral thesis (Massuanganhe, 2016).

Processes on taphonomy affect the diatom frustules during both sedimentation and

accumulation. Examples of these are chemical corrosion and reworking, which may result in

physical breakage and redistribution/re-accumulation of frustules (e.g. Behrensmeyer et al.,

2000; Hassan et al., 2006; Korhola, 2007). In the discussion above regarding the salinity

gradient it is suggested that diatom analyses of surface sediments may underestimate

contemporary salinity conditions within Subarea 1. This fact was established as relations

between marine and brackish species differ in samples from surface sediments and surface

water within the investigated area, which most likely is caused by taphonomic processes.

Before discussing probable processes within the lower Save River, it is notable that there is a

difference in the time period represented by surface water samples and surface sediment

samples. The surface water in the river is in constant motion and captured diatoms

represent only the time interval when the sample was collected. Each surface sediment

sample represent an unknown time period, however, substantially longer.

According to Fritz et al. (1993), Gasse et al. (1997), Reed (1998), Ryves et al. (2006) and

Ryves et al. (2009) poor preservation of diatoms is a potential reason to why diatom

analyses of buried sediments may generate misrepresentative salinities. A well-known

problem in brackish and/or marine conditions involves chemical dissolution of diatom

frustules (Flower, 1993; Straub, 1993; DeMaster & Pope, 1996; Bradshaw et al., 2005; Ryves

et al., 2006). Parts of the Save River delta is occupied by mangrove forest, which takes up

dissolved silica from sediments (e.g. Fulweiler & Nixon, 2005; Struyf & Conley, 2008; Epstein,

2009). High uptake may cause chemical corrosion of the inorganic amorphous silica that

builds up the frustules of diatoms in sediments (Castro et al., 2013; Ryves et al., 2013; Struyf

45

& Conley, 2008; Epstein, 2009; Das et al., 2014). The absence of unusually small frustules in

earlier accumulated sediments can be related to longer exposure-time to vegetative uptake

of silica. Thereby smaller diatoms may have been fully dissolved, resulting in a relative

increase in larger and more robust frustules. Dissolution and fragmentation of frustules are

suggested to potentially be caused by high bacterial activity (Bidle & Azam, 1999; Struyf et

al., 2005) and zooplankton grazing (Levin et al., 1999; Cohen, 2003). During high uptake of

silica in sediments (e.g. Fulweiler & Nixon, 2005; Struyf & Conley, 2008; Epstein, 2009)

and/or river flooding (Jacobs et al., 2013) the soil can be under-saturated in silica. This can

further limit diatom growth and cell division (Furnas, 1990; Round et al., 1990; Martin-

Jézéquel et al., 2000; Cohen, 2003; Litchman et al., 2008), which can be an additional cause

to the unusually small-sized diatoms.

Barker et al. (1990) suggest chemical corrosion to increase during alkaline conditions and

higher salinities. Fore & Grafe (2002) have identified several alkaliphilic diatom species in

Idaho, USA, which are also recognized in the present study. Examples of these taxa are

Aulacoseira granulata, Fragilaria construens, F. construens v. venter, F. brevistrata, F.

pinnata, F. leptostaruron, Navicula mutica, N. goeppertiana, Cyclotella meneghiniana,

Gyrosigma attenatum, Epthemia turgida, E. sorex, Rhopalodia gibba, Cocconeis placentula

and Surirella brebisonii. Gasse (1986) have also classified Hantzschia amphioxys, Nitzschia

sigma, Navicula smithii, Cyclotella striata and Campylodiscus clypeus as alkaliphilic from

samples collected in eastern Africa. These taxa are also identified in samples from the

present study, thus indicating alkaline conditions in the lower Save River. The increased pH

may derive from the underlying calcium-rich bedrock (Schetselaar et al., 2008). Mixture of

acidic water from the upper drainage system and alkaline water in the lower part and in the

delta may imply neutral pH in the studied area, which is indicated by two pH measurements.

As the diatom taxa indicate conditions of higher pH, local variations are most likely

occurring. Alkaline environments can thus be an additional cause to the absence of thinly

silicified frustules since these taxa are not easily preserved under such conditions. This is

supported by Reed (1998) who suggests that increased dissolution in alkaline conditions can

lead to absence of certain taxa, thus biasing the interpretation. Further, Cohen (2003) state

high pressure may also increase dissolution. Increased pressure may affect diatom frustules

at the deepest parts of a river channel. Note that none surface water sample in present

46

study was collected from depths exceeding 50 cm. Sediment could, however, have been re-

suspended and re-deposited after previous burial under deep water conditions.

Chaetoceros spp is one of the most common marine genus of diatoms (Round et al., 1990)

and have been identified in the northwestern Indian Ocean (e.g. Thorrington-Smith, 1971;

Sorokin et al., 1985; Vidya et al., 2013). Furthermore, Chaetoceros spp also exist in brackish

water conditions (Rijstenbil & Merks, 1981; Nwadiaro & Ezefili, 1986; Risberg, 1990) and

were therefore expected in the sediment samples from the delta area. As species of this

genus are thinly silicified they are less resistant to chemical corrosion and easily completely

dissolved. Further, the lack of vegetative cells of Chaetoceros spp in the present study

indicates that they have been dissolved in the delta. The absence of resting spores of

Chaetoceros spp may support presence of increased dissolution of silica within the

sediments, which is suggested in sub-chapter 5.1 Taxonomy. This statement is supported by

investigations in the St Helena Bay, South Africa where it is suggested that sediment traps

and samples from sediment/water interface were dominated by resting spores (cf. Pitcher,

1986). The water column, however, contained abundant vegetative cells. Further, a

relationship between authigenic mineral formation and biogenic silica may be present in

deltaic environments. This is suggested to occur either through direct conversion of the

siliceous diatom frustules or as a part of the precipitation of authigenic aluminosilicate

(Chamely & Millot, 1972; Hurd, 1973; Van Bennekom & Van der Gaast, 1976; Badaut &

Risarcher, 1982; Cole, 1985; Banfield et al., 1991). Thus, portions of biogenic silica are

potentially converted to and/or replaced by K- and Fe-rich aluminosilicate minerals in

depositional areas (Mackenzie & Garrels, 1966; Wollast & de Broeu, 1971; Ristvet, 1978;

Michalopoulos & Aller, 1995; Michalopoulos et al., 2000). This process may be an additional

cause to why sediment in the Save River delta is not representing current water salinity

conditions.

The Save River delta is a dynamic environment with tides and re-occurring flooding events,

which generate turbulent water and reworking of sediments (Overeem & Syvitski, 2009).

Strong winds can also cause resuspension of sediment and thus diatoms (cf. Mitbavkar &

Anil, 2002). During dynamic conditions diatom frustules are vulnerable for breakage, but

they may also be reworked and accumulated elsewhere. Compaction of sediments may be a

47

contributory cause of breakage, especially regarding thinly silicified frustules. Further,

mangrove roots are suggested to trap sediments more effectively than other vegetation

(Scoffin, 1970), which may cause fast compaction of sediments. Several deltaic wetland

areas are today experiencing less sediment supply due to damming of upstream rivers

(Syvitski et al., 2009). In the drainage system of Save River a number of dams have been

constructed, e.g. in Insiza River, Zimbabwe (Kileshye Onema et al., 2006) implying that

preservation could be more favorable at present. According to Sherrod (1999) and Sawai

(2001) the taphonomic problems of dynamic environments is widespread in tidal

environments and may cause inaccurate interpretations of salinity (Denys, 1994). This can be

a possible explanation for the mixture of diatom species, concerning their optimal salinity,

within the lower Save River. Reworking and re-distribution of sediment may also occur due

to fluctuations of the halocline, i.e. salinity stratification. During rising flooding conditions,

until high tide, heavier saline water reaches into river channels as an expanding tongue

along the bottom (e.g. Largier & Taljaard, 1991; Schumann & Pearce, 1997). Theoretically,

sediments and accumulated diatoms, which include planktonic, benthic, living and fossils,

could be redistributed through resuspension and/or redepositing when the halocline

oscillates (Figure 18).

48

Figure 18. An interpretation of how the salinity stratification and position of a halocline can vary during different tidal conditions within the Save River delta. Diatom frustules within the oval areas may be re-distributed and re-deposited during changes of tidal conditions. 10 km represents the distance diatoms may be transported in the Save River delta, i.e. approximately between M4 and M11. The upper picture displays positioning of the stratification and the halocline during low tide. The gradient between the freshwater and the brackish water are relatively steep and the heavier saline water do not reach far into the delta. The lower picture shows the position during high tide. Saline water expands further into the delta and the gradient is not as steep as during low tide.

This process assumes, however, that both the solid and dashed ovals (Figure 18) are located

within an accumulation area. Within the Save River delta it seems as diatoms may be

transported along a c. 10 km long stretch, approximately between M4 and M11, caused by

tidal processes. This implies that freshwater and brackish taxa, both living and fossil, could

be mixed along this section. These scenarios are only possible if the photic zone reaches

below the halocline. The before proposed underestimation of contemporary salinity

conditions in surface sediments within subarea 1, may partly be caused by the varying

position of the halocline.

All sample categories show similarity regarding the most common diatom communities, e.g.

Thalassiosira eccentrica, Nitzschia granulata, Hantzschia distinctepunctata, Diploneis sp., D.

interrupta, D. pseudovalis, Cyclotella sp. and Melosira nummuloides (cf. Appendix 3). Note

49

that these taxa represent brackish or marine conditions. Especially brackish species occur in

samples from Subareas 1-3 (Figure 1). Further, this distribution of brackish taxa can be

related to taphonomic effects caused by fluctuating halocline as discussed above. Brackish

species may have been redeposited during high tide when saline water reaches further into

the delta and the river channel. Note, however, that the number of identified brackish taxa

is varying and occasional frustules may have been brought by birds (Atkinson, 1980;

Figuerola & Green, 2002) and/or human activities (Hallegraeff & Bolch, 1992; Rothlisberger

et al., 2010; Kilroy & Unwin, 2011).

5.4 OSL and radiocarbon dating

At site M9 two samples for OSL-dating were collected, M9 and M9V. Despite the difference

in depth (330 cm and 180 cm) they indicate similar ages, i.e. 920 ± 90 yrs and 890 ± 100 yrs

BP, respectively. OSL-dates at site P2 (Massuanganhe et al., 2016a) also indicate equal ages

at two different depths; c. 250 yrs at 500 cm and 200 cm depths. Ages at deeper depths are

expected to show older ages, however, the related OSL-ages at M9 and P2 can be explain by

reworking of sediments. Similar ages may also be a result of high accumulation rates

between samples (cf. Roberts et al., 2001). Minerals may furthermore be partly incomplete

bleached, commonly occurring in fluvial environments. Incomplete bleaching can imply

overestimated ages and explain the minor difference of ages, despite different depths

(Preusser et al., 2008).

Radiocarbon samples at P2 (Massuanganhe et al., 2016a) do not show ages in chronological

order. At 410 cm depth the sample indicate an age of c. 750 cal. yrs BP, however,

radiocarbon age at 310 cm depth indicate c. 1500 cal. yrs BP. Reverse radiocarbon dates may

be a result from reworking and storage of sediments or hard water effect, commonly

occurring in deltas and fluvial environments (Stanley & Hait, 2000).

During interpretations of buried sediments in field a geographically extensive clay layer was

been noted. These layers are also identified by Massuanganhe et al. (2016a) and interpreted

as mangrove forest habitat. This interpretation is based on observations of present fine

grained sediments accumulated in mangrove areas. Fine grained layers identified in the

50

present study are also suggested to represent mangrove environments and the analysis thus

corresponds to Massuanganhe et al. (2016a).

5.5 Future studies

To further increase knowledge about the diatom flora of the lower Save River, following

suggestions would be beneficial to add into future investigations.

Collect samples from the bottom of the river channel.

Repeated sampling during different seasons and tidal conditions.

Measurements of the conductivity and pH.

Geochemical analysis of silica in water and sediment.

Hydrological measurements of the Save River; magnitude of river flow, suspended

material and tidal water.

Diatom cultivation in tanks, to distinguish optimal environmental conditions.

Additional OSL- and radiocarbon ages.

Study more frustules with ESEM.

Additional research on Cyclotella sp. and Diploneis sp. to identify them to species

level.

51

6. Conclusions

The investigation resulted in 68 diatom genera and 263 species. In general, characteristic

species are Nitzschia granulata, N. littoralis, Hantzschia distictepunctata, Cyclotella sp.,

Thalassiosira eccentrica, Diploneis sp. and D. interrupta. In Subarea 1 typical species are

Cyclotella sp., C. stylorum and Nitzschia littoralis. In Subarea 2 characteristic species are

Amphora libyca, Diploneis interrupta and Hantzschia distinctepunctata. Characteristic

species in Subarea 3 are Aulacoseira alpigena, Diploneis interrupta and Hantzschia

amphioxys.

Two commonly occurring diatom taxa were not possible to identify to species level;

Diploneis sp. and Cyclotella sp. These are associated with brackish water conditions based on

geographical occurrences and accompanying species compositions. Furthermore, small

species of Opephora spp, Nitzschia spp, Navicula mutica, Navicula spp and Melosira

nummuloides are identified.

Diatom analysis indicates that there is a latitudinal decline in salinity from east to west.

Generally, Subarea 1 is characterized by marine and brackish species. In Subarea 2

indifferent and brackish taxa occur while Subarea 3 is dominated by brackish, indifferent and

freshwater species. There are indications of a transition from ocean water influences to

more fluvial conditions at the area around M11, i.e. close the boundary Subarea 1 and

Subarea 2. Diatom assemblages from surface sediments suggest an underestimation of

prevalent salinity conditions within Subarea 1 as they do not correspond to communities

growing on mangrove cortex. These species are interpreted to be more representative for

salinity conditions as they consist of merely benthic species.

Processes on the taphonomy are interpreted to be the main reason for the underestimations

of salinity in Subarea 1. The lower Save River is affected by several geomorphological

processes and is underlain by calcareous bedrock causing alkaline conditions. Reworking of

sediments and chemical corrosion are suggested to be dominant taphonomic processes

biasing interpretations. Prevalent conditions in the lower Save River indicated that

interpretations based on diatom analysis should be treated with caution. Samples collected

from benthic habitats (cortex) and water is suggested to be more reliable compared to

52

surface and buried sediments. Further studies are recommended before interpretations of

sediments can be used with confidence.

7. Acknowledgement

I would like to thank my supervisor Jan Risberg at the Department of Physical Geography for

supporting me in my initiative to write my master thesis about the lower Save River. Jan has

also assisted during field work and helped during laboratory work, diatom analysis and the

writing process. I would also like to thank Elidio Massuanganhe at Eduardo Mondlane

University, Maputo, for invaluable support during field work and geomorphological

interpretation during the analysis. Thanks to Lars-Ove Westerberg at the Department of

Physical Geography, who participated in the field work, and to the boat driver Albino Vasco

Chidala. I would like to thank Annika Berntsson and Christos Katrantsiotis at the Department

of Physical Geography and David Siqueiros-Beltrones at the National Polytechnic Institute,

Mexico City, for indispensable help during diatom analysis. Last but not least I would like to

thank Marika Wennbom and Sven Karlsson at the Department of Physical Geography and

Marianne Ahlbom at the Department of Geological Sciences for technical assistance of GIS,

light microscopes and ESEM. Stefan Bjursäter at the Department of Physical Geography has

performed the laboratory preparations and the measurements of the OSL samples and

interpreted the ages.

53

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9. Appendix 1. Basic data used to construct the pie charts in Figures 8-10. Groups are

according to optimal salinity and numbers are identified diatom frustules; absolute and

relative. Sites are presented from east to west in the following order: surface water samples,

surface sediment samples and mangrove cortex samples.

Surface water samples

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Mangrove cortex samples Surface sediment samples

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10. Appendix 2. The species list includes identified diatom taxa from surface sediments,

surface water, buried sediments and mangrove cortex in the lower Save River, Mozambique.

Years for author names were not possible to find for all species. Ecology: A – Marine taxa, B – Brackish taxa, C – Halophilic taxa, D – Indifferent taxa, E – Freshwater taxa, F – Aerophilic taxa, G – Unknown taxa, H – Extinct taxa Habitat: B – Benthic, P – Planktonic, T – Tychoplanktonic

Taxa Ecology Habitat

Achnanthes brevipes C. Agardh 182468 A B

Achnanthes danica (Flögel) Grunow 188068 A B

Actinocyclus normanii (Gregory) Hustedt 195718 A P

Actinoptychus senarius Ehrenberg 184350 A P

Actinoptychus splendens (Shadbolt) Ralfs in Pritchard 18613 A T

Amphora acutiscula Kützing 184468 A B

Amphora arenaria Donkin 185868,55 A B

Amphora ostrearia v. vitrea Cleve 18958 A B

Amphora proteus Gregory 185719 A B

Amphora richardiana B.J Cholnoky 19688,12 A B

Amphora spectabilis Gregory 185768 A B

Amphora ventricosa Gregory 18574 A B

Anomoeoneis sphaerophora v. costata (Kützing) Schmid 197725 A B

Bacillaria paradoxa Gmelin 179126 A B

Biddulphia antediluviana (Ehrenberg) Van Heurck, 188534 A B

Biddulphia aurita (Lyngbye) Brébisson 183832 A B

Biddulphia plana A. Schmidt 18888 A B

Biddulphia rhombus (Ehrenberg) W. Smith 18542 A B

Caloneis bicuneata (Grunow) Boyer 192736 A B

Campylodiscus bicostatus W. Smith ex Roper 185467 A B

Campylodiscus clypeus Ehrenberg 184468 A B

Campylodiscus fastuosus Ehrenberg 18458,31 A B

Cocconeis disculoides Hustedt 195556 A B

Coscinodiscus argus Ehrenberg 183916 A P

Coscinodiscus decipiens Grunow ex Van Heurck 188246 A P

Coscinodiscus lineatus Ehrenberg 18393 A P

Coscinodiscus radiatus v. parvus Grunow 18843 A P

Cosinodiscus asteromphalus Ehrenberg 184466,15 A B

Cyclotella stylorum Brightwell 186024,39,70 A T

Delphineis minutissima (Hustedt) Simonsen53,51 A B

Dimeregramma minor (Gregory) Ralfs 186168 A B

Diploneis caffra Giffen23 A B

Diploneis smithii (Brébisson) Cleve 189425 A B

Diploneis suborbicularis (Gregory) Cleve 189468 A B

Diploneis weissflogii (A. Schmidt) Cleve 189468 A B

Eunotogramma frauenfeldii Weisse 18458,30 A B

Eunotogramma marinum (W.Smith) Peragallo 190868 A B

Eunotogramma sp. Weisse 185568 A B

Fallacia nummularia (Greville) D.G Mann 199037 A B

Fragilaria capensis Grunow 181968 A B

Fragilaria schultzii Brockmann 195024 A B

Grammatophora angulosa v. islandica Ehrenberg 18418,30 A B

Grammatophora hamulifera Kützing 184468 A B

Huttoniella reichardtii (Grunow) Hustedt 195568 A B

Hyalodiscus scoticus (Kützing) Grunow 187968 A B

Lyrella abrupta (Gregory) D.G Mann 199068 A B

Lyrella amphoroides D.G. Mann 197868 A B

Lyrella impercepta (Hustedt) Moreno 199668 A B

Lyrella lyra (Ehrenberg) Karayeva 197868 A B

Mastogloia elliptica (C.A. Agardh) Cleve 189368 A B

Mastogloia elliptica v. dansei (Thwaites) Cleve 189525 A B

Mastogloia obliqua Hagelstein 185669 A B

Mastogloia omissa Voigt 195244,8 A B

Mastogloia smithii Thwaites 185668 A B

Navicula alpha Cleve 189369 A B

Navicula fauta Hustedt 182268 A B

Navicula monilifera Cleve 18958 A B

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Navicula xi v. Peltoides (Hendey) Hustedt8 A B

Navicula yarrensis Grunow 187633 A B

Neofragilaria nicobarica Desikachary, Prasad & Prema 197868 A B

Nitzschia granulata Grunow in Cleve & Möller68 A B

Nitzschia marginulata Grunow in Cleve & Möller68 A B

Nitzschia navicularis (Brébisson) Grunow 188068 A B

Nitzschia ocellata Cleve & Müller 188068 A B

Nitzschia panduriformis Gregory 185768 A P

Nitzschia sigmaformis Hustedt 195568,6 A P

Opephora minuta (A.Cleve) A.Witkowski; Lange-Bertalot & Metzeltin 200068 A B

Opephora pacifica (Grunow) Petit 188868 A P

Opephora schwarzii (Grunow) Petit8,68 A P

Paralia sulcata (Ehrenberg) Cleve 187368 A B

Plagiogramma pulchellum (Greville) Peragallo 185968 A B

Plagiogramma staurophorum (Gregory) Heiberg 186368 A B

Pleurosigma decorum W. Smith 185358 A B

Pleurosira laevis v. polymorpha (Ehrenberg) Compère 198224 A B

Podosira stelligera (Bailey) A. Mann 19073 A B

Psammodiscus nitidus (Gregory) Round & Mann 198068 A B

Rhaponeis amphiceros (Ehrenberg) Ehrenberg 184468 A B

Rhaponeis castracanii Grunow 184430 A B

Rhopalodia musculus (Kützing) O. Müller 190068 A B

Rhopalodia pacifica Krammer68 A B

Stephanopyxis spp (Ehrenberg) Ehrenberg 18453 A unknown

Surirella fastuosa (Ehrenberg) Kützing 184368 A B

Surirella gemma Ehrenberg 184020 A B

Thalassiosira eccentrica Ehrenberg 190438,9,13 A P

Thalassiosira oestrupii (Ostenfeld) Hasle 196010 A B

Thalassiosira symmetrica G.A. Fryxell & Hasle 19739 A P

Trachyneis aspera (Ehrenberg) Cleve 189468 A B

Trachysphenia australis Hustedt 19558,4 A B

Triceratium reticulum Ehrenberg 184468 A B

Achnanthes delicatula (Kützing) Grunow 188068 B B

Achnanthes parvula (Kützing) 184468 B P

Actinoptychus adriaticus Grunow 186330 B B

Actinoptychus grundleri A. Schmidt8 B P

Actinoptychus sp. Ehrenberg 18438 B B

Amphora coffeaeformis (C.A. Aargard) Kützing 184468 B B

Amphora staurophora Juhlin-Dannfelt 188268 B B

Anomoeoneis sphaerophora (Ehrenberg) Pfitzer 187125 B B

Auliscus sculptus (W. Smith) Brightwell 186068,5 B B

Biddulphia spp S.F Gray 182124 B B

Caloneis permagna (Baily) Cleve 189425 B P

Campylodiscus sp. Ehrenberg 184468 B B

Cocconeis scutellum Ehrenberg 183868 B B

Coscinodiscus spp Ehrenberg 183924,45 B P

Cyclotella caspia Grunow 187824,17,40 B P

Cyclotella crassa Tynni 198363 B P

Cyclotella sp (Kützing) Brébisson 193824 B P

Cyclotella striata Kützing 184411,21,24 B P

Cyclotella striata v. bipunctata Fricke 190024 B P

Delphineis surirella (Ehrenberg) G.W Andrews 200971 B B

Diploneis bombus Ehrenberg 185368 B B

Diploneis chersonensis (Grunow) Cleve 189230 B B

Diploneis crabro Ehrenberg 185468 B B

Diploneis didyma (Ehrenberg) Cleve 183968 B B

Diploneis incurvata (Gregory) Cleve68 B B

Diploneis interrupta Ehrenberg 185425,1,52 B B

Diploneis nitescens (Gregory) Cleve 189468 B B

Diploneis psuedovalis Hustedt 193068 B B

Diploneis sp Hustedt 193025 B B

Diploneis stroemii Hustedt 193768 B B

Entomoneis alata C. G. Ehrenberg 184568 B B

Entomoneis spp Ehrenberg 184525 B B

Eunotogramma laeve (W.Smith) Peragallo 187968 B B

Grammatophora macilenta W. Smith 185668 B B

Grammatophora oceanica Ehrenberg 184068 B B

Grammatophora sp. Ehrenberg 184068 B B

Gyrosigma balticum (Ehrenberg) Rabenhorst 185325 B B

Gyrosigma nodiferum (Grunow) Reimer 196625 B B

Gyrosigma wansbeckii (Grunow) Cleve 189425 B B

Hantzschia distinctepunctata Hustedt 192124 B B

Hantzschia marina (Donkin) Grunow 188068 B B

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Hyalodiscus sp. Ehrenberg 184068 B B

Mastogloia exigua Lewis 186168 B B

Mastogloia fallax Cleve68 B B

Mastogloia peragalli Cleve68 B B

Melosira moniliformis (O.F. Müller) C.A. Agardh 182468 B B

Melosira nummuloides (Dillwyn) Aagardh 182424 B B

Navicula lyra Ehrenberg 184165 B B

Navicula normaloides Cholnoky 196862,68 B B

Navicula nummularia Greville 185970 B B

Navicula pusilla W. Smith 185325,72 B B

Nitzschia calida Grunow 188068,41 B B

Nitzschia circumsuta (Bailey) Grunow 187868 B B

Nitzschia cocconeiformis Grunow in Cleve & Möller 188068 B B

Nitzschia hungarica Grunow 186268 B B

Nitzschia hybrida Grunow 188068 B B

Nitzschia levidensis (W. Smith) Grunow 188168 B B

Nitzschia levidensis v. victoriae (Grunow) Cholnoky68 B B

Nitzschia littoralis Grunow 188068,24 B B

Nitzschia obtusa W. Smith 185368 B P

Nitzschia obtusa v. kurzii (Rabenhorst) Grunow68 B B

Nitzschia sigma (Kützing) W. Smith 185326,46 B P

Nitzschia tryblionella W. Smith 185326 B B

Opephora mutabilis (Grunow) Sabbe & Vyverman 195568 B B

Petrodictyon gemma (Ehrenberg) D.G. Mann 199068 B B

Pleurosigma spp W. Smith 185225 B B

Pleurosira laevis (Ehrenberg) Compère 198268 B B

Rhopalodia acuminata Krammer 198768 B B

Terpsinoë americana (Bailey) Ralfs 186847,54 B B

Thalassiosira spp Cleve 187324 B P

Trachysphenia sp. Petit 187768 B B

Triceratium spp Ehrenberg 183968 B B

Amphora crucifera A. Cleve 193268 C B

Amphora pediculus (Kützing) Grunow 188025 C B

Cyclotella meneghiniana Kützing 184424 C P

Epithemia turgida (Ehrenberg) Kützing 184426 C B

Nitzschia sigma v. sigmatella Grunow 187826 C P

Amphora copulata (Kützing) Schoeman & Archibald 198628 D B

Amphora libyca Ehrenberg 184028 D B

Amphora ovalis Kützing 184428 D B

Caloneis bacillum (Grunow) Cleve 189425 D B

Caloneis molaris (Grunow) Krammer 198525 D B

Caloneis silicula (Ehrenberg) Cleve 189425 D B

Cocconeis placentula Ehrenberg 183827 D B

Cocconeis placentula v. euglypta (Ehrenberg 1854) Grunow 188427 D B

Coscinodiscus nitidus W. Gregory 18573,43 D P

Cyclotella distinguenda Hustedt 192724 D P

Cymbella aspera (Ehrenberg) Pergallo 184925 D B

Denticula kuetzingii Grunow 186226 D B

Diploneis ovalis (Hilse) in Cleve 189125 D B

Epithemia adnata (Kützing) Brébisson 183826 D B

Epithemia argus (Ehrenberg) Kützing 184426 D B

Epithemia cistula (Ehrenberg) Ralfs in Pritchard 186126 D B

Epithemia smithii Carruthers 186426 D B

Epithemia sorex Kützing 184426 D B

Fragilaria brevistriata Grunow in Van Heurck 188124 D B

Fragilaria construens (Ehrenberg) Grunow 186226 D B

Fragilaria construens v. construens (Ehrenberg) Hustedt 195726 D B

Fragilaria construens v. venter (Ehrenberg) Hustedt 195726 D B

Fragilaria dilatata (Brébisson) Lange-Bertalot 198626 D B

Fragilaria leptostauron v. martyi (Héribaud) Lange-Bertalot 199126 D B

Gyrosigma attenatum (Kützing) Rabenhorst 185325 D B

Navicula capitata Ehrenberg 183825 D B

Navicula cuspidata (Kützing) Kützing 184425,29 D B

Navicula integra (W. Smith) Ralfs in Pritchard 186125 D B

Navicula rhynchocephala Kützing 184425 D B

Nitzschia amphibia Grunow 186226 D B

Rhopalodia gibba (Ehrenberg) O. Müller 189524 D B

Rhopalodia gibba v. parallella (Grunow) H. & M. Peragallo26 D B

Rhopalodia operculata (Agardh) Håkansson 197926 D B

Surirella brebissonii Krammer & Lange-Bertalot 198724 D B

Achnanthes lanceolata v. frequentissima Lange-Bertalot 199127 E B

Amphora inariensis Krammer 198025 E B

Aulacoseira alpigena (Grunow) Krammer 199024,7 E P

74

Aulacoseira ambigua (Grunow) Simonsen 197924 E P

Aulacoseira crassipunctata Krammer 199026 E P

Aulacoseira distans (Ehrenberg) Simonsen 197926 E P

Aulacoseira granulata (Ehrenberg) Simonsen 197924 E P

Aulacoseira spp Thwaites 184824,26 E P

Capartogramma crucifera (Grunow ex Cleve) Ross 196335 E B

Cocconeis neodiminuta Krammer 199127 E B

Cymatopleura solea (Brébisson) W. Smith 185126 E B

Cymbella affinis Kützing 184425 E B

Cymbella ehrenbergii Kützing 1844 (Agardh) Cleve 189425 E B

Cymbella lacustris (Agardh) Cleve 189425 E B

Cymbella laevis Naegeli in Kützing 184925 E B

Cymbella meulleri Hustedt 193825 E B

Cymbella silesiaca Bleich in Rabenhorst 186425 E B

Cymbella spp C. Agardh 183025 E B

Cymbella tumida (Brébisson) Van Heurck 188025 E B

Diploneis elliptica (Kützing) Cleve 189125 E B

Diploneis puella Cleve 189425,1 E B

Diploneis subovalis Cleve 189425 E B

Eunotia didyma Grunow 191324,42 E B

Eunotia minor (Kützing) Grunow in Van Heurck 188126 E B

Eunotia pectinalis (Kützing) Rabenhorst 186426 E B

Eunotia pectinalis v. undulata (Ralfs) Rabenhorst 186426 E B

Eunotia praerupta Ehrenberg 184324,14 E B

Eunotia soleirolii (Kützing) Rabenhorst 186424 E B

Eunotia spp Ehrenberg 183724 E B

Fragilaria biceps (Kützing) Lange-Bertalot 199124 E B

Fragilaria pinnata Ehrenberg 184348 E B

Fragilaria ulna Lange-Bertalot 198024 E B

Fragilaria virescens Ralfs 184326 E B

Fragilaria zeilleri Gasse 198011 E B

Gomphonema affine Kützing 184427 E B

Gomphonema augur v. turris (Ehrenberg) Lange-Bertalot 198527 E B

Gomphonema cleveIi Fricke 190227 E B

Gomphonema spp Ehrenberg 183227 E B

Gyrosigma acuminatum (Kützing) Rabenhorst 185357 E B

Gyrosigma obtusatum (Sullivant & Wormley) Boyer 192211 E B

Gyrosigma wormleyi (Sullivant) Boyer 192222 E B

Navicula brasiliana (Cleve) Cleve 189425 E B

Navicula confervacea (Kützing) Grunow 188025 E B

Navicula constans v. symmetrica Hustedt 195725 E B

Navicula cryptotenella Lange-Bertalot 198525 E B

Navicula laevissima v. laevissima Kützing 184425 E B

Navicula pupula Kützing 184425 E B

Navicula pupula v. nyassensis (O. Müller) Lange-Bertalot 198525 E B

Navicula radiosa Kützing 184425 E B

Navicula tuscula Ehrenberg 184125 E B

Neidum iridis (Ehrenberg) Cleve 189425 E B

Nitzschia palea (Kützing) W. Smith 185626 E B

Nitzschia sinuata v. delognei (Grunow) Lange-Bertalot 198026 E B

Nitzschia valdecostata Lange-Bertalot & Simonsen 197826 E B

Nitzschia vermicularis (Kützing) Hantzsch 186026 E B

Pinnularia divergens W. Smith 185325 E B

Pinnularia maior (Kützing) Rabenhorst 185325 E B

Pinnularia spp Ehrenberg 184325 E B

Pinnularia trevelyana (Donkin) Rabenhorst 18648 E T

Pinnularia viridis v. caudata Boyer 191625 E B

Rhopalodia gibberula (Ehrenberg) O. Müller 189924 E B

Rhopalodia gibberula v. globosa Hustedt60 E B

Rhopalodia vermicularis O. Müller11 E B

Stauroneis anceps Ehrenberg 184325,49 E P

Stauroneis phoenicenteron (Nitzsch) Ehrenberg 184325 E B

Stauroneis spp Ehrenberg 184325 E B

Stephanodiscus minutulus (Kützing) Cleve & Möller 187826 E P

Stephanodiscus sp. Ehrenberg 184626 E P

Surirella linearis W. Smith 185326 E B

Achnanthes inflata (Kützing) Grunow 184427 F B

Hantzschia amphioxys (Ehrenberg) Grunow in Cleve & Grunow 188014 F B

Navicula goeppertiana (Bleisch) H.L. Smith 1874-187925 F B

Navicula mutica v. undulata Cleve & Möller 1877-188264 F B

Navicula mutica Kützing 184425 F B

Navicula paramutica Bock 196325 F B

Pinnularia borealis Ehrenberg 184325 F B

75

Stauroneis obtusa Lagerstedt 187325 F B

Achnanthes spp Bory 182227 G B

Amphora spp Ehrenberg ex Kützing 184427 G B

Anorthoneis sp. Grunow 186827 G P

Caloneis spp Cleve 198425,27 G B

Cocconeis spp Ehrenberg 183627 G B

Cosmioneis sp. D.G Mann & Stickle 199027 G P

Cyclotella spp (Kützing) Brébisson 183824 G P

Diploneis spp Ehrenberg ex Cleve 189425 G B

Epithemia spp Kützing 184426,27 G B

Fallacia spp Stickle & D.G Mann 199027 G B

Fragilaria spp Lyngbye 181926 G B

Frustulia undosa D.Metzeltin & Lange-Bertalot 199835 G B

Gyrosigma spp Hassall 184525,27 G B

Hantzschia sp. Grunow 187727 G B

Lyrella sp. Karajeva 197827 G B

Mastogloia spp Thwaites 185627,68 G B

Navicula spp Bory 182225 G P

Nitzschia cf. valdecostata Hassall 184526 G B

Nitzschia spp Hassall 184525,26 G B

Opephora spp P. Petit 188924,68 G T

Stauroneis cf. obtusa Lagerstedt 187325 G B

Surirella spp Turpin 182826,27 G B

Synedra spp Ehrenberg 183026,27 G B

Varia G unknown

Aulacodiscus sp. Ehrenberg 184459,3,61 H P

1Alfinito et al. (1990), 2Asmus (1982), 3Cleve-Euler (1951), 4Çolak Sabanci & Koray, 2010, 5Dawson & Smith (2000), 6Donadel

et al. (2016), 7Dunck et al. (2012), 8Foged (1975), 9Fryxell & Hasle (1972), 10Fryxell & Hasle (1980), 11Gasse (1986),

12Gottschalk et al. (2007), 13Harris et al. (1995), 14Harwood (1986), 15Hasle & Lange (1992), 16Hasle & Sims (1986), 17Hasle

(1962), 18Hasle (1977), 19Hassan et al. (2006), 20Hendrarto & Nitisuparjo (2010), 21Håkansson (1996), 22Jackson & Lowe

(1978), 23Kokociński et al. (2009), 24Krammer & Lange-Bertalot (1991a), 25Krammer and Lange-Bertalot (1986), 26Krammer

and Lange-Bertalot (1988), 27Krammer and Lange-Bertalot (1991b), 28Levkov, (2009), 29Cohn et al. (1989), 30Lopez Fuerte et

al. (2010), 31López-Fuerte et al. (2015), 32Marshall (1976), 33Maynard (1968), 34Mereschkowsky (1901), 35Metzeltin (1998),

36Miho & Witkowski (2005), 37Moura et al. (2007), 38Naya (2012), 39Ng & Sin (2003), 40Ta et al. (2001), 41Pan et al. (2006),

42Patrick (1940), 43Pednekar et al. (2011), 44Pennesi et al. (2012), 45Rattray (1890), 46Redekar & Wagh (2000), 47Risberg

(1986), 48Round (1965), 49Round (1972), 50Ryu et al. (2005), 51Sabbe (1993), 52Sandgren et al. (1999), 53Sar et al. (2007), 54Sato

et al. (2001), 55López-Fuerto et al. (2013), 56Soylu et al. (2007), 57Stefano & Marino (2003), 58Sterrenburg (1995),

59Sterrenburg et al. (2014), 60Strelnikova et al. (2004), 61Taukulis & John (2006), 62Tiffany (2008), 63Trobajo et al. (2004),

64Tynni (1983), 65Van de Vijver & Mataloni (2008), 66Van Heurck (1896), 67Werner (1971), 68Virah-Sawmy et al. (2009),

69Witkowski et al. (2000), 70Yabe et al. (2004), 71Zalat (2001), 72Zong & Horton (1998), 73Zong & Horton (1999).

11. Appendix 311. Appendix 311. Appendix 311. Appendix 3 Counted diatom frustules from all samples from M- and P sites are here presented. Surface sediment samples are marked with brown color, surface water

samples with blue and mangrove cortex samples with green. M-samples are counted by the author 2016. Samples in P1, P2, P3, P6 and P8 is counted by Berntsson and the author 2015.

M1

M2

M3

M4

M6

M7

M8

M9

22

7 c

m

M9

22

2 c

m

M9

21

7 c

m

M9

21

2 c

m

M9

20

7 c

m

M9

20

2 c

m

M9

19

7 c

m

M9

15

0 c

m

M1

0

M1

1

M1

2a

M1

2b

M1

4 4

68

cm

M1

4 4

79

cm

M1

4 4

93

cm

M1

4 5

00

cm

M1

5

M1

7

M1

8

M1

9

M2

0 3

60

cm

M2

1

M2

2

M2

5 0

cm

M2

5 1

50

cm

M2

5 2

90

cm

M2

5 3

00

cm

M2

8

M2

9

M3

0

M3

1

M3

2

M1

H2

O

M2

H2

O

M3

H2

O

M4

a H

2O

M4

b H

2O

M5

H2

O

M6

H2

O

M9

H2

O

M1

0 H

2O

M1

1 H

2O

M1

2 H

2O

M1

3 H

2O

M1

4 H

2O

M1

9 H

2O

M2

0 H

2O

M2

3 H

2O

M2

4 H

2O

M2

6a

H2

O

M2

6b

H2

O

M2

8 H

2O

M2

9 H

2O

M3

2 H

2O

M1

co

rte

x

M2

co

rte

x

M3

co

rte

x

M4

co

rte

x

M5

co

rte

x

Achnanthes brevipes A 1 6 1 1 5.5 2

Achnanthes danica A 1

Actinocyclus normanii A 2

Actinoptychus

senariusA 1

Actinoptychus

splendensA 6 13 2.5 6 4.5 1 1 25 3 25 1 7 7 1 2 1 2 1 1 1 1 1 1 6 3.5 9 1

Amphora arenaria A 2

Amphora ostrearia

v. vitreaA 1 1

Amphora proteus A 1 1

Amphora richardiana A 1 3 1 1

Amphora ventricosa A 8 1 5 1 3 1 1 1 1 1 1 4 3 2.5

Biddulphia

antediluvianaA

Biddulphia aurita A 3 1 1 1 1

Biddulphia plana A 2 2 1 2.5

Biddulphia rhombus A 6 7.5 2 2

Caloneis bicuneata A 1

M-samples               

Depth

Sample

Taxa                          Ecology

76

Caloneis bicuneata A 1

Campylodiscus

bicostatusA

Campylodiscus

fastuosusA 1 2

Cocconeis disculoides A 1.5 3 1 3

Coscinodiscus

asteromphalusA 18 11 3.5 30.5 5 8 2 30 1 6 11 14 4 4 5 1.5 5.5 8 5 5 2 4 2 1 2 2.5 1 1 14 8 6.5 9 1

Coscinodiscus lineatus A 2 1 1 2

Cyclotella stylorum A 36 10 1 87 61 5.5 38 16 41

Delphineis

minutissimaA 1 1

Dimeregramma

minorA

Diploneis caffra A 3 1 4 1 2 1 1 2.5 3

Diploneis smithii A 4.5 15 14 4 3 2 14 1 2 2 1 9 6 1 1 6.5 1 4 4 3 1 1 6 8 4.5 7.5 10 2 6 5

Diploneis

suborbicularisA 3 2 1 66 2 1.5 1

Diploneis weissflogii A 1 1 3

Eunotogramma

frauenfeldiiA 2 1.5

76

M1

M2

M3

M4

M6

M7

M8

M9

22

7 c

m

M9

22

2 c

m

M9

21

7 c

m

M9

21

2 c

m

M9

20

7 c

m

M9

20

2 c

m

M9

19

7 c

m

M9

15

0 c

m

M1

0

M1

1

M1

2a

M1

2b

M1

4 4

68

cm

M1

4 4

79

cm

M1

4 4

93

cm

M1

4 5

00

cm

M1

5

M1

7

M1

8

M1

9

M2

0 3

60

cm

M2

1

M2

2

M2

5 0

cm

M2

5 1

50

cm

M2

5 2

90

cm

M2

5 3

00

cm

M2

8

M2

9

M3

0

M3

1

M3

2

M1

H2

O

M2

H2

O

M3

H2

O

M4

a H

2O

M4

b H

2O

M5

H2

O

M6

H2

O

M9

H2

O

M1

0 H

2O

M1

1 H

2O

M1

2 H

2O

M1

3 H

2O

M1

4 H

2O

M1

9 H

2O

M2

0 H

2O

M2

3 H

2O

M2

4 H

2O

M2

6a

H2

O

M2

6b

H2

O

M2

8 H

2O

M2

9 H

2O

M3

2 H

2O

M1

co

rte

x

M2

co

rte

x

M3

co

rte

x

M4

co

rte

x

M5

co

rte

x

Eunotogramma

marinumA 1

Fallacia nummularia A 5

Fragilaria capensis A 1

Grammatophora

angulosa v. islandicaA 1

Grammatophora

hamuliferaA 1

Huttoniella reichardtii A 1 1 1 1 1 2 1 2 2 3 2 4 1 1 1

Lyrella abrupta A 2

Lyrella amphoroides A 1 1

Lyrella lyra A 1

Mastogloia oblique A 3.5

Mastogloia omissa A 3 1

Navicula alpha A 8 3 1 1 1 4 1 3.5 2.5 1 4

Navicula monilifera A 1.5 1 1 1 1 1

Navicula yarrensis A 2 2 2

Nitzschia granulata A 4 107 5.5 20 10 40 47 1 7 30 1 3 21 30 7 1 19 2 1 1 1 1 3 12 23 2 2 2 2 1 1 1

Nitzschia marginulata A 2 1

Nitzschia navicularis A 18 28 2.5 3 5 2 3.5 1 1 2 1 3.5 1.5 3 1 2 3 1 2 5 2 6.5 1 1 1 1.5 2 4 11 1

Nitzschia ocellata A 2

Nitzschia

panduriformisA 1 2 1 1 2 1 1 1 1

77

panduriformis

Nitzschia

sigmaformisA 1

Opephora minuta A 3.5

Opephora pacifica A 1 1 3

Paralia sulcata A 1 5 13 3.5 15 7 2 1 11 16 15 1 1 4 14 6 4.5 34 1 1 3 1 4 2 3 9.5

Plagiogramma

pulchellumA 1 1 1 1 1 1 1

Pleurosigma decorum A 1 3.5

Pleurosira laevis A 49 8 3.5 3 3

Podosira stelligera A 3

Psammodiscus nitidus A 1 1

Rhaponeis

amphicerosA 1 2 1 4

Rhaponeis castracanii A 1 1

Rhopalodia musculus A 8 1 1 1 1 1 1 1 6 13

Rhopalodia pacifica A

Stephanopyxis spp A 2 1 1 1 4 5 1 4 9 16 2 10 17 15

Surirella fastuosa A 1 1 1

Surirella gemma A 1 1

77

M1

M2

M3

M4

M6

M7

M8

M9

22

7 c

m

M9

22

2 c

m

M9

21

7 c

m

M9

21

2 c

m

M9

20

7 c

m

M9

20

2 c

m

M9

19

7 c

m

M9

15

0 c

m

M1

0

M1

1

M1

2a

M1

2b

M1

4 4

68

cm

M1

4 4

79

cm

M1

4 4

93

cm

M1

4 5

00

cm

M1

5

M1

7

M1

8

M1

9

M2

0 3

60

cm

M2

1

M2

2

M2

5 0

cm

M2

5 1

50

cm

M2

5 2

90

cm

M2

5 3

00

cm

M2

8

M2

9

M3

0

M3

1

M3

2

M1

H2

O

M2

H2

O

M3

H2

O

M4

a H

2O

M4

b H

2O

M5

H2

O

M6

H2

O

M9

H2

O

M1

0 H

2O

M1

1 H

2O

M1

2 H

2O

M1

3 H

2O

M1

4 H

2O

M1

9 H

2O

M2

0 H

2O

M2

3 H

2O

M2

4 H

2O

M2

6a

H2

O

M2

6b

H2

O

M2

8 H

2O

M2

9 H

2O

M3

2 H

2O

M1

co

rte

x

M2

co

rte

x

M3

co

rte

x

M4

co

rte

x

M5

co

rte

x

Thalassiosira

eccentricaA 2 3 5 12 13 2 7 10 6 11 6 4 2 4 1 13 3 7 15 29 11 4 13 23 3.5 2 1.5 24 47 90 56 4 53 6 19

Thalassiosira

oestrupiiA 2 16

Thalassiosira

symmetricaA

Trachyneis aspera A 20 2 10 3 2.5 1.5 1 1 1 3 13

Trachysphenia

australisA 2 2 1

Triceratium reticulum A 1 2 1 2 1 1

Achnanthes delicatula B 8 1 1 1 1 2

Achnanthes parvula B 1

Actinoptychus

adriaticusB 12 2.5 1 1 1 1 1

Actinoptychus sp. B 1

Amphora

coffeaeformisB 10 1 6 1 1 1 1 1 1 2 2 7 3

Amphora

staurophoraB 29 1

Anomoeoneis

sphaerophoraB 2

Auliscus sculptus B 1 1 1 1 1 1

Biddulphia spp B 3

Caloneis permagna B 1 1 3.5 1 2 2 2

Camplyodiscus sp. B 1

Cocconeis scutellum B 4 3 1

78

Cocconeis scutellum B 4 3 1

Coscinodiscus spp B 5 2 3 1 2 1 5

Cyclotella caspia B 27 15 7 9 5 5 2 4 13 7 1 1 4 5

Cyclotella crassa B 2 4 1 5 4 2 1 3 2 1 1 1 2

Cyclotella striata B 2 8 3 5

Cylotella sp. B 43 22 1 41 27 2.5 14 34 154 11 22 1 1 2 3 65 45 41 42 8 11 22 73 6

Delphineis surirella B 1 1.5

Diploneis bombus B 1

Diploneis

chersonensisB 5 2 1 1 1 4 1

Diploneis crabro B 1

Diploneis incurvata B 2

Diploneis interrupta B 2 5 1 10 2.5 3.5 6 1 1 7.5 4 2 5 6 41 3 13 7 10 2 2 10 3 6 1 3 3 9.5 2 5 1 1 1 2 2 4.5 10 2 2 4.5 8 1 3

Diploneis nitescens B 1

Diploneis sp. B 79 1 1 9 1 5 5 4 11 6 1 5 1 4 70 3 1 2 4 28 33 2 4 14 10 20 23 14 17 51 5 9 91

Diploneis stroemii B 4

Entomoneis alata B 6.5 1 46 1 2 42 2

Entomoneis spp B 1 1

78

M1

M2

M3

M4

M6

M7

M8

M9

22

7 c

m

M9

22

2 c

m

M9

21

7 c

m

M9

21

2 c

m

M9

20

7 c

m

M9

20

2 c

m

M9

19

7 c

m

M9

15

0 c

m

M1

0

M1

1

M1

2a

M1

2b

M1

4 4

68

cm

M1

4 4

79

cm

M1

4 4

93

cm

M1

4 5

00

cm

M1

5

M1

7

M1

8

M1

9

M2

0 3

60

cm

M2

1

M2

2

M2

5 0

cm

M2

5 1

50

cm

M2

5 2

90

cm

M2

5 3

00

cm

M2

8

M2

9

M3

0

M3

1

M3

2

M1

H2

O

M2

H2

O

M3

H2

O

M4

a H

2O

M4

b H

2O

M5

H2

O

M6

H2

O

M9

H2

O

M1

0 H

2O

M1

1 H

2O

M1

2 H

2O

M1

3 H

2O

M1

4 H

2O

M1

9 H

2O

M2

0 H

2O

M2

3 H

2O

M2

4 H

2O

M2

6a

H2

O

M2

6b

H2

O

M2

8 H

2O

M2

9 H

2O

M3

2 H

2O

M1

co

rte

x

M2

co

rte

x

M3

co

rte

x

M4

co

rte

x

M5

co

rte

x

Eunotia didyma B 1

Eunotogramma laeve B 2 2 2 1 1 1 1 1 1

Grammatophora

macilentaB 1

Grammatophora

oceanicaB 1 1

Grammatophora sp. B

Gyrosigma balticum B 1

Gyrosigma nodiferum B 4 1

Gyrosigma

wansbeckiiB 27 2.5

Hantzschia

distinctepunctataB 9 1 3 3 3 3 12 17 1 2 2 2.5 32 3.5 1 88 1 29 11 9 27 6 30 1 3 1

Hantzschia marina B 6 3 1 11 2 1.5 4

Hantzschia marina B 1

Mastogloia exigua B 3 1

Mastogloia fallax B 2

Mastogloia peragalli B 1

Melosira moniliformis B 1 6 7 4 7 3 8 1 18 8 21 11

Melosira

nummuloidesB 21 179

Navicula lyra B

Navicula normaloides B 12 19

Navicula nummularia B 1 1 2

79

Navicula pusilla B 1

Nitzschia calida B 1

Nitzschia

cocconeiformisB 10 5.5 1

Nitzschia hybrida B 1

Nitzschia levidensis B 3 1 5 1 5 2 1 1

Nitzschia littoralis B 1 9 135 3 1 17 2 2 2 1 3 2 1 8 7 10 5 63 1

Nitzschia obtusa

v. kurziiB 1 2 1 2

Nitzschia sigma B 2 2 2

Nitzschia trybionella B 4

Opephora mutabilis B 1 1

Petrodictyon gemma B 2

Pleurosigma spp B 6 9 1

Rhopalodia

acuminataB 2 1 1 5

Terpsinoë

americanaB 1 14 4 1 1 1 1

Thalassiosira spp B 7 5 3 3 5 9 3 2 7.5 11 6 1

79

M1

M2

M3

M4

M6

M7

M8

M9

22

7 c

m

M9

22

2 c

m

M9

21

7 c

m

M9

21

2 c

m

M9

20

7 c

m

M9

20

2 c

m

M9

19

7 c

m

M9

15

0 c

m

M1

0

M1

1

M1

2a

M1

2b

M1

4 4

68

cm

M1

4 4

79

cm

M1

4 4

93

cm

M1

4 5

00

cm

M1

5

M1

7

M1

8

M1

9

M2

0 3

60

cm

M2

1

M2

2

M2

5 0

cm

M2

5 1

50

cm

M2

5 2

90

cm

M2

5 3

00

cm

M2

8

M2

9

M3

0

M3

1

M3

2

M1

H2

O

M2

H2

O

M3

H2

O

M4

a H

2O

M4

b H

2O

M5

H2

O

M6

H2

O

M9

H2

O

M1

0 H

2O

M1

1 H

2O

M1

2 H

2O

M1

3 H

2O

M1

4 H

2O

M1

9 H

2O

M2

0 H

2O

M2

3 H

2O

M2

4 H

2O

M2

6a

H2

O

M2

6b

H2

O

M2

8 H

2O

M2

9 H

2O

M3

2 H

2O

M1

co

rte

x

M2

co

rte

x

M3

co

rte

x

M4

co

rte

x

M5

co

rte

x

Trachysphenia sp. B 1

Triceratium spp B 1 1

Cyclotella

meneghinianaC 1 1 1 2 7 2 2

Amphora libyca D 4 2 3 6 1 15 13 1 10 1 5

Amphora ovalis D 1

Coscinodiscus nitidus D 2

Cyclotella

distinguendaD 1

Diploneis ovalis D 2

Epithemia adnata D 3.5

Fragilaria brevistriata D 1 1

Gyrosigma attenatum D 3.5 1 1 1

Rhopalodia gibba D 1 1 4.5 1.5 1 1 1

Surirella brebissonii D 3 2 2 3 4

Aulacoseira alpigena E 255

Aulacoseira ambigua E 4

Aulacoseira granulata E 1

Aulacoseira spp E 9

Cymbella spp E 1 3 2 1 4

Diploneis didyma E 1 1 1

Diploneis elliptica E 17

Diploneis puella E 3 10

80

Diploneis puella E 3 10

Diploneis subovalis E 2

Eunotia praerupta E 1

Fragilaria pinnata E 18

Fragilaria ulna E 1

Fragilaria zeilleri E

Gyrosigma

acuminatumE 4 3 23

Navicula brasiliana E 2

Pinnularia spp E 1 1

Pinnularia trevelyana E 1

Rhopalodia gibberula E 1 1 1

Rhopalodia gibberula

v. globosaE

Stauroneis anceps E 1

Hantzschia amphioxys F 1 1 1 1 1 22 27 1.5 1

Navicula mutica F 6 2 1 1 23.5

Navicula mutica

v. undulataF 1 1 1 4

80

M1

M2

M3

M4

M6

M7

M8

M9

22

7 c

m

M9

22

2 c

m

M9

21

7 c

m

M9

21

2 c

m

M9

20

7 c

m

M9

20

2 c

m

M9

19

7 c

m

M9

15

0 c

m

M1

0

M1

1

M1

2a

M1

2b

M1

4 4

68

cm

M1

4 4

79

cm

M1

4 4

93

cm

M1

4 5

00

cm

M1

5

M1

7

M1

8

M1

9

M2

0 3

60

cm

M2

1

M2

2

M2

5 0

cm

M2

5 1

50

cm

M2

5 2

90

cm

M2

5 3

00

cm

M2

8

M2

9

M3

0

M3

1

M3

2

M1

H2

O

M2

H2

O

M3

H2

O

M4

a H

2O

M4

b H

2O

M5

H2

O

M6

H2

O

M9

H2

O

M1

0 H

2O

M1

1 H

2O

M1

2 H

2O

M1

3 H

2O

M1

4 H

2O

M1

9 H

2O

M2

0 H

2O

M2

3 H

2O

M2

4 H

2O

M2

6a

H2

O

M2

6b

H2

O

M2

8 H

2O

M2

9 H

2O

M3

2 H

2O

M1

co

rte

x

M2

co

rte

x

M3

co

rte

x

M4

co

rte

x

M5

co

rte

x

Pinnularia borealis F 1 1 5

Achnanthes spp G 5.5 1 1 1 1

Amphora spp G 14 13 1 1 1 1 1 4 1 2 1 2 2 3

Anorthoneis sp. G 1

Caloneis spp G 2 1 1 1

Cocconeis spp G 6 1 1 1 1 1 1 1

Cosmoneis sp. G 1

Cyclotella spp G 2 2

Diploneis spp G 2 7 1 1 3 1 1

Epithemia spp G 1 1 1

Fallacia spp G 7

Gyrosigma spp G 1 1 7.5 1 1 2 1 1 2 1

Hantzschia sp. G 1

Lyrella sp. G 1

Mastogloia spp G 1 1 2 1

Navicula spp G 2 6.5 5 9 1 1 1 1 3 2 1 5 3 1 1 1 2 1 2 3 1

Nitzschia spp G 3 13 2 1.5 2 1 2 2 3 1.5 1 2 2 1 2 1 1 71 1 6

Opephora spp G 1 1 64

Surirella spp G 1 1 1 1 1.5 1

Synedra spp G 1 1 1

Varia G 2.5 3 4 2.5 2 3 2 3 5 2 3 2 3 3 5 2 1 5 1 3.5 1 1 1 5 2 3 1 6

Aulacodiscus sp. H 1

81

Aulacodiscus sp. H 1

81

P1Depth (cm)

Taxa Ecology 5 15 35 45 55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215 225 235 245 255 265 275 285 295 305 315 325 335 345 355

Amphora ventricosa A 1

Coscinodiscus argus A 1 1,5

Coscinodiscus radiatus v.parvus A 1 2,5

Diploneis smithii A 9

Diploneis suborbicularis A 1 3

Hyalodiscus scoticus A 3

Navicula fauta A 1

Nitzschia granulata A 1 7 1 10 8 7

Nitzschia navicularis A 2 2,5 1 1 1

Opephora schwarzii A 1

Paralia sulcata A 2 2 3 2

Plagiogramma staurophorum A 1

Psammodiscus nitidus A 1 1

Actinopticus adriaticus B 2 2

Anomoeoneis shaeorophora B 1

Caloneis permagna B 4

Cocconeis scutellum B 1

Cyclotella sp. B 1

Cyclotella striata B 1

Diploneis interrupta B 2 1 2,5 1,5 9 11 20 7,5 27,5 45 28,5

Diploneis psuedovalis B 1 1 5 76

Diploneis sp. B

Eunotogramma laeve B 1

Hantzschia distinctepunctata B 8 13,5

Hyalodiscus sp. B 5 8 14 1

Nitzschia cocconeiformis B 23,5 1

Nitzschia levidensis B 4

Nitzschia littoralis B 2 8,5

Cyclotella meneghiniana C 1

Epithemia turgida C 2

Nitzschia sigma v. sigmatella C 1

Amphora copulata D 3,5 9 47

Caloneis bacillum D 2 2

Caloneis silicula D 2

Denticula kuetzingii D 3 3 2

Diploneis ovalis D 8

Epithemia adnata D 3,5 8,5 4,5

Epithemia cistula D 1

Fragilaria brevistriata D 6

Fragilaria construens D 10

Fragilaria dilatata D 1

Fragilaria leptostauron v. martyi D 1

Navicula cuspidata D 1 1

Navicula integra D 1 1

Nitzschia amphibia D 1 3

Rhopalodia gibba D 1 3,5 6,5

Rhopalodia operculata D 2 7

Aulacoseira ambigua E 1

Aulacoseira granulata E 1,5

Aulacoseira spp E 5

Cocconeis neodiminuta E 1

Cymbella ehrenbergii E 1 1

Cymbella lacustris E 1

Cymbella laevis E 1

Cymbella meulleri E 1 1 4

Cymbella silesiaca E 2 2

Cymbella spp E 2

Diploneis elliptica E 9

Eunotia pectinalis v. undulata E 1

Eunotia spp E 2

Fragilaria biceps E 1 1

Fragilaria ulna E 13

Gomphonema affine E 1

Gyrosigma obtusatum E 10

Navicula constans v. symmetrica E 1

Navicula cryptotenella E 2

Nitzschia sinuata v. delognei E 2

Pinnularia spp. E 1 3

Pinnularia viridis v. caudata E 1

Rhopalodia gibberula E 1

Rhopalodia vermicularis E 2

Stauroneis spp E 2

Hantzschia amphioxys F 1 7

Navicula goeppertiana F 3

Pinnularia borealis F 1 1 4 1

Stauroneis obtusa F 1

Amphora spp. G 1 2 2

Epithemia spp G 1,5

Frustulia undosa G 1

Hantzschia sp. G

Navicula spp G 3

Nitzschia spp G 3

Varia G 3 2,5 1 1 16 13

P2/M14Depth (cm)

Taxa Ecology 245 255 265 275 285 295 305 315 325 335 345 355 365 375 385 395 405 415 425 435 445 455 465 468 (M14) 475 479 (M14) 485 493 (M14) 500 (M14)Amphora acutiscula A 1Amphora spectabilis A 2

Anomoeoneis sphaerophora v. costata A 1 1Bacillaria paradoxa A 1Biddulphia aurita A 1 1Campylodiscus bicostata A 1 1Coscinodiscus argus A 1 1 3Coscinodiscus decipiens A 1

Coscinodiscus radiatus v. parvus A 1 1 1,5 2 16Cosinodiscus asteromphalus A 1,5 2Cyclotella stylorum A 5Cymbella aspera A 1Diploneis caffra A 1 2 1 6 1 1Diploneis smithii A 2 6Lyrella lyra A 1Mastogloia elliptica A 1 1

Mastogloia elliptica v. dansei A 1Mastogloia smithii A 1Neofragilaria nicobarica A 1Nitzschia granulata A 1 1 1 2 1 1 1 11 1 5,5 41 4 1Nitzschia navicularis A 2Paralia sulcata A 5 3 22 1,5 1 1,5 1

Pleurosira laevis v. polymorpha A 1Rhaponeis amphiceros A 1

Stephanopyxis spp A 1Trachyneis aspera A 1Triceratum reticulum A 1 1Actinoptychus adriaticus B 1 3 1Actinoptychus grundleri B 1

Actinoptychus sp. B 1Anomoeoneis sphaerophora B 1 1 2Caloneis permagna B 1 2 1 1 1 1 1Cocconeis scutellum B 1

Coscinodiscus sp. B 1 1 2Cyclotella crassa B 1

Cyclotella striata v. bipunctata B 1Diploneis interrupta B 9 33 23,5 18,5 31 30 16 6,5 15 9 26,5 18,5 11 36,5 56,5 36,5 9,5 88,5 43 14 97 67 7,5 41 20,5 2,5 12 12,5 7Diploneis pseudovalis B 3 2 1 1 3 5,5 1 1 2 2 1 79 21,5 80,5 30,5 3,5

Diploneis sp. B 4Hantzschia distinctepunctata B 3,5 5,5 5,5 4 5 11,5 2,5 2 1,5 5,5 4 6,5 4 4,5 5 4 5 16,5 4 3 1 19 28 17 24 1 9,5 2 1,5

Hyalodiscus sp. B 1 1 1 1 2 1 1Melosira moniliformis B 4Navicula normaloides B 1Nitzschia circumsuta B 1 2 3

Nitzschia hungarica B 1

Nitzschia levidensis v. victoriae B 1 1,5 1Nitzschia littoralis B 1Nitzschia obtusa B 1 2Rhopalodia acuminata B 1 1 2,5 1 1 2 1,5 2,5 1 1 1 1 1 1 1,5 2Amphora crucifera C 2Amphora pediculus C 3Cyclotella meneghiniana C 1 2 2,5 1 3 1 1,5 2 1,5 1 2 2 4 9 1 2,5 1 1 1Epithemia turgida C 1 1 2Amphora copulata D 1 5 7 4 1 5 3 4 9 5 13 3 2 1 7 2,5 1 3 14 17,5 2,5Amphora libyca D 3 4 1 1 1 3Amphora ovalis D 1 1 1 1Caloneis bacillum D 3 1 1Caloneis molaris D 1 3 1 2Caloneis silicula D 5Cocconeis placentula D 1 1

Cocconeis placentula v. euglypta D 1 1,5Denticula kuetzingii D 1,5 2 2 3 1 1 1,5 1 4,5 1 4 1 1Epithemia adnata D 2 3,5 9,5 11,5 1,5 9,5 6 9,5 12 3 6,5 4,5 3 5 6 1,5 11,5 6,5 2 6 4,5 3,5 1,5 1Epithemia argus D 2,5Epithemia cistula D 1Epithemia smithii D 1 1Epithemia sorex D 1 2 1Fragilaria brevistriata D 5 2 3 1 2 3 6 2 2Fragilaria construens D 1 1

Fragilaria construens v. construens D 2,5 1 2 1 3 1 1 1 2 2 8 2

Fragilaria construens v. venter D 2 2 5 2 1 5Navicula capitata D 2Navicula cuspidata D 1 3 10,5 1 1 10 1 1 1 1 1 1 1Navicula integra D 1 1 2Navicula rhynchocephala D 1Nitzischia amphibia D 1 1 1 1Rhopalodia gibba D 1 2 6 1,5 2 3 2,5 5,5 4 5,5 3,5 4 1 2 1,5 1 3,5 2,5 1,5 1 1 8,5 2 4,5 1,5 2 1,5

Rhopalodia gibba v. parallella D 1 1,5Rhopalodia operculata D 1

Suriella brebissonii D 1

Achnanthes lanceolata v. frequentissima E 1Amphora inariensis E 1 3 2Aulacoseira ambigua E 1 1 3 1Aulacoseira crassipunctata E 1 1 2Aulacoseira distans E 3Aulacoseira granulata E 6 3 1 11 1 4,5 1 2 3 3 2 1 1 4 1 2 6 1 3 4

Aulacoseira spp E 1 2 2 1 2 1 1 1 2Carpartogramma crucifera E 2 2 1 1 1,5 1 2 1Cocconeis neodiminuta E 1Cymatopleura solea E 1 1 1 1Cymbella affinis E 1 1 1Cymbella ehrenbergii E 1 1 1 1 3 3Cymbella meulleri E 1 2 3 1 1,5 3 4 2 1Cymbella silesiaca E

Cymbella spp E 1 1 4 1 1 2 1Cymbella tumida E 1Diploneis elliptica E 1 5 3 3 1 4,5 1 1 1 3 1 2Eunotia minor E 1Eunotia pectinalis E 2Eunotia soleirolii E 1 1

Eunotia spp E 1 2,5 4 2,5 3 2 2 2,5 2 3,5 1 2,5 1 1 1 1,5 1,5 2 1,5 1Fragilaria pinnata E 1Fragilaria ulna E 1 1 3 1,5 1 3 2 1,5 6 3 3,5 2,5 1 2,5 3 2 1 3 1 2 1 1Fragilaria virescens E 2

Gomphonema augur v. turris E 4Gomphonema cleveii E 1 1 1

Gomphonema spp E 3 1 2Gyrosigma acuminatum E 3Gyrosigma obtusatum E 1 1 1 1 7 7 10,5 31,5 1Gyrosigma wormleyi E 7,5Navicula confervacea E 2

Navicula laevissima v. laevissima E 1Navicula pupula E 1 1 1

Navicula pupula v. nyassensis E 1Navicula radiosa E 1 1 1 1 1

Navicula tuscula E 1Neidum iridis E 1Nitzschia palea E 3Nitzschia valdecostata E 2Nitzschia vermicularis E 1Pinnularia divergens E 1Pinnularia maior E 1

Pinnularia spp E 1 1 2 4 2 1 3 5 1,5 1,5 1 1 1 1Rhopalodia gibberula E 3Rhopalodia vermicularis E 1 1 1 1 1Stauroneis anceps E 1 1 1 2 3 1 1 1Stauroneis phoenicenteron E 1

Stauroneis spp E 2 1 1 1 1Stephanodiscus minutulus E 1

Stephanodiscus sp. E 1Suriella linearis E 1Achnanthes inflata F 1

Achnanthes spp F 2Hantzschia amphioxys F 8,5 5 3,5 4 2,5 3 3 6 4 3,5 3 5 1 3 5 1 3 2 2,5 4 1 6 1 2Navicula mutica F 1 4 2 2,5 1 2 1 1 1 1 1,5 1 3 1Pinnularia borealis F 3 1,5 1 3,5 2 1,5 1 1 1 1,5 2 3 2 2,5 2,5 6 2 1 1 1 2 1 1

Amphora spp G 1 1 1 1 5 4 1

Caloneis spp G 1 2 1

Cyclotella sp. G 1 2

Diploneis spp G 3 4 1

Epithemia spp G 1,5 1 1 1

Fragilaria spp G 1 1 1 1 2

Gyrosigma spp G 3,5 1

Hantzschia sp. G 3Lyrella impercepta G 1

Mastogloia spp G 1

Navicula spp G 1,5 3 3

Nitzschia cf. valdecostata G 2 3

Nitzschia spp G 1 2 1 2 1 2 1 2 2 2 1

Opephora spp G 1

Suriella spp G 1 1 1

Synedra spp G 1 1 1Varia G 1,5 1,5 1,5 5 1 1 1 1 1,5 6 2,5 4 1 2 3,5 6 1 3 2 1 3 1

P3Depth (cm)

Taxa Ecology 105 115 125 135 145 155 175 185 195 303 308 313 350 365

Campylodiscus clypeus A 1

Coscinodiscus radiatus v. parvus A 1 3 3

Cosinodiscus asteromphalus A 1

Diploneis caffra A 6 1 3

Diploneis smithii A 3

Fragilaria schultzii A 1

Nitzschia granulata A 1 1 1 5,5 10 19,5 1 1

Nitzschia navicularis A 1 1

Paralia sulcata A 4,5 4,5 19,5 22 3

Rhaponeis amphiceros A 1

Actinoptychus adriaticus B 2 1 1 2

Diploneis interrupta B 3 1,5 9 8 1 1 3 1,5 17 14,5 11 10,5 4,5

Diploneis pseudovalis B 2 2 9 1

Hantzschia distinctepunctata B 1 1 1 6 3,5 1,5 1

Hyalodiscus sp. B 1 1 4 26 1

Melosira nummuloides B 1

Terpsinoë americana B 1

Cyclotella meneghiniana C 1 1 2 1 1

Amphora copulata D 2

Caloneis bacillum D 2

Cyclotella distinguenda D 1

Denticula kuetzingii D 1

Diploneis ovalis D 1

Epithemia adnata D 2 1,5 1,5 1,5

Fragilaria brevistriata D 8

Fragilaria construens v. venter D 2

Navicula cuspidata D 1

Navicula integra D 1

Rhopalodia gibba D 1

Aulacoseira granulata E 1 1 3 1

Cymbella affinis E 1

Cymbella spp E 2

Diploneis elliptica E 1

Eunotia spp E 1 1,5 1 5,5

Fragilaria ulna E 1

Gomphonema spp E 1

Gyrosigma obtusatum E 2

Pinnularia spp E 3

Hantzschia amphioxys F 31,5 1 3 24,5 1 1

Navicula goeppertiana F 2

Navicula mutica F 1 3 6 4,5 1

Navicula paramutica F 2,5 7,5

Pinnularia borealis F 1 1 1,5 1

Stauroneis cf. obtusa F 1

Caloneis sp. G 1

Fragilaria spp G 2

Lyrella sp. G 1

Navicula spp G 2

Nitzschia spp G 2

Varia G 2 1 1

P6Depth (cm)

Taxa Ecology 5 15 25 35 45 55 65 75 85 95 105 115 125 135 145 152 167 194 220 240 250 280 300 320 340 350 360 380 400

Eunotogramma frauerfeldii A 2

Eunotogramma sp. A 1,5

Navicula xi v. peltoides A 2 1

Paralia sulcata A 6,5 5,5 3,5 1 1 5 11,5

Psammodiscus nitidus A 1

Actinoptychus adriaticus B 1 1

Diploneis interrupta B 9 1 3 5,5 1 1,5

Hyalodiscus sp. B 5 2

Nitzschia cocconeiformis B 1 1 1 5

Terpsinoë americana B 3 8,5 4,5 2 3,5 3

Cyclotella distinguenda D 1

Hantzschia amphioxys F 1,5

Navicula goeppertiana F 1

Navicula mutica F 8,5

Pinnularia borealis F 8 1 1

Lyrella sp. G 1 1

P8Depth (cm)

Taxa Ecology 5 15 25 35 45 55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215 225

Diploneis caffra A 1

Nitzschia granulata A 1

Paralia sulcata A 4

Diploneis interrupta B 1 2 1

Hyalodiscus sp. B 15 4

Terpsinoë americana B 1

Hantzschia amphioxys F 2,5 15

Navicula goeppertiana F 1

Navicula mutica F 5,5 17

Pinnularia borealis F 4,5 17

Nitzschia spp G 2

85

12. Appendix 4. Micrographs of Cyclotella sp. Pictures 1-4 are from ESEM and 5-6 are from

light microscope. For discussion on taxonomy see Table 2.

86

13. Appendix 5. Micrographs of Diploneis sp. Pictures 1-2 are from ESEM and 3-4 are from

light microscope. For discussion on taxonomy see Table 3.

87

14. Appendix 6. Micrographs of diatom species from the lower Save River. Pictures 1-7 are

from ESEM and 8-9 are from light microscope.

88