Biological Condition of the Ring and Stitt Riversepa.tas.gov.au/documents/taswater, rosebery wwtp - appendix l2... · Biological condition of the Stitt River and L Pieman in relation

Biological condition of the Stitt River and L Pieman in relation to the

TasWater Rosebery WWTP discharge: Survey of aquatic biota, Autumn 2013.

Report to TasWater

PE Davies and LSJ Cook August 2013

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Table of Contents

1. Introduction and Aims ................................................................................................ 1

2. Methods ....................................................................................................................... 5

2.1 Field sampling – Stitt River .................................................................................. 5 2.2 Field sampling – Lake Pieman .............................................................................. 7

2.3 Data analysis ....................................................................................................... 11

3. Results: Stitt River ................................................................................................. 12 3.1 Macroinvertebrates ............................................................................................. 12

3.2 Stitt River – Habitat conditions ........................................................................... 16 3.3 Stitt River – Vertebrates ...................................................................................... 16

4. Results Lake Pieman ................................................................................................. 19 4.1 Algae ................................................................................................................... 19

4.2 Macroinvertebrates ............................................................................................. 21

5. Overall Biological Condition .................................................................................... 26 5.1 Stitt River ............................................................................................................ 26

5.2 Lake Pieman ........................................................................................................ 26

6. References ................................................................................................................. 27

TasWater Stitt River and Lake Pieman aquatic biota survey, 2013 1

Biological condition of Stitt River and L Pieman:

Survey of aquatic biota, Autumn 2013 Peter E Davies and Laurie Cook

Freshwater Systems

82 Waimea Avenue Sandy Bay Tasmania 7005

1. Introduction and Aims

This report describes the results of a freshwater biological survey conducted in autumn

2013 in the Stitt River and Lake Pieman.

The primary aims of this monitoring are to:

describe the status of macroinvertebrate and fish assemblages in the lower Stitt

Rivers, as they pertain to the future discharge of a proposed TasWater wastewater

treatment;

describe the ecological status of lake shore habitats of Lake Pieman, as they relate

to the possible effect of the proposed new TasWater wastewater treatment plant

on the discharge of the Stitt River into the Lake.

This survey is related to an ongoing, routine biomonitoring program conducted for MMG

(Mining and Minerals Resource Group) in the Stitt River and Lake Pieman, which is

focused on the effects of the discharge of both historical and current mine wastewaters on

the biota of the two receiving environments. Surveys under this latter program have been

conducted for autumn and spring annually from 2005 to 2013, and provide important

contextual data for this TasWater survey.

Several sites in the Stitt River have been sampled for fish and benthic macroinvertebrates

as part of the routine monitoring program for MMG. An additional site was added to the

lowest reach of Stitt River in autumn 2013 for this TasWater report, as a possible future

location to assess the impacts of the proposed WWTP discharge in the Stitt.

15 sites were sampled in the shore zone of the upper arm of Lake Pieman for benthic

algae and macroinvertebrates, again as part of the routine monitoring program for MMG.

Three additional sites were sampled in Lake Pieman in autumn 2013 in the vicinity of the

Stitt River discharge to the lake, as the basis for ongoing assessment of any likely effect

of the proposed TasWater WWTP discharge to the Stitt on the lake.

This report documents the autumn 2013 survey data at TasWater sites, and places them

into context using the data from the MMG program (with whom TasWater has a data

sharing agreement).


Context and sampling considerations:

Lake Pieman

The Bobadil discharge enters the upper arm of Lake Pieman on its eastern shore,

approximately 5 km downstream respectively of Hydro Tasmania’s Bastyan dam on Lake

Rosebery. This discharge is managed by MMG and contains combinations of treated

mine and mine-site wastewater, as well as treated town sewage. Town sewage (managed

by TasWater) is currently pumped from the town sewerage network to the 2 and 5

Tailings Dam (Bull Dam) adjacent to the middle reaches of the Stitt River. From there it

is pumped to the Bobadil Tailings Dam.

The upper arm of Lake Pieman is frequently highly ‘fluvial’ (river-like) and experiences

large and fluctuating flow rates throughout the year. It also experiences substantial

fluctuations in level which are mainly dictated by seasonal variation in inputs to the lake

from its catchment and variations in power station throughput at Lake Pieman’s Reece

Dam.

The mixing behaviour of the Bobadil discharge in the lake is locally complex, with

periods of rapid downstream dispersion and dilution during releases from the Bastyan

power station and/or spill from Lake Rosebery, as well as periods of relative stagnation in

which a measure of local pooling and multidirectional dispersion occurs within the

receiving lake reach, especially in near surface waters. This is also likely to be the case

with the discharge of Stitt River water to Lake Pieman. This means that localized

biological effects of these discharges may be manifest both ‘upstream’ and ‘downstream’

of the point of discharge in the lake, though with impacts likely to occur in a

predominantly downstream direction.

Lake Pieman is a steep, drowned river valley in its upper reaches, with its bottom

comprised predominantly of bedrock/boulders and drowned forest debris. It is not

possible to sample this area for fauna either systematically or safely. Benthic algae and

fauna associated with lake edges and near-surface snags can however be sampled readily

(Davies et al. 2005) from a boat and have been routinely monitored for the MMG

program since 2005.

Nutrient levels in the Bobadil discharge are high relative to background levels in Lake

Pieman. Nutrient levels may also be raised slightly in the lower Stitt River due to the

combination of town storm water and Bull Dam discharge/seepage. These inputs of

nutrients to Lake Pieman may locally enhance benthic algal production in the shoreline

areas of the lake adjacent to the discharge locations, depending on light availability

(shading) and the toxicity of other discharge components.

Lake benthic algal growth is limited to well lit, shallow shore zones, since light

attenuation by high levels of natural dissolved organic compounds is strong. Bowling et

al. (1986) reported attenuation to the point that euphotic depths (depths to which

photosynthetically active radiation, or PAR, could penetrate and stimulate algal growth)

in humic western Tasmanian lakes were only of the order of 0.5 to 2 m depth. Enhanced

algal growth resulting from any WWTP discharge will occur primarily in the surface


zone and on fixed surfaces which experience regular exposure to the discharge (Davies et

al. 2005).

The shoreline of the lake is complex and highly variable in substrate stability and

composition, making it unsuitable for systematic benthic algal sampling. Surfaces of tree

snags located away from the immediate shading effect of overhanging forest provide a

suitable habitat for algal sampling. Such sampling can provide information on the relative

magnitude of algal biomass and the longitudinal extent of any enhancement along the

shoreline (though not across the lake surface).

Surface filamentous algal growth can act as a surrogate indicator for the influence of the

nutrient-rich discharges on the assumption that:

the local flux of nutrients is large enough for the spatial extent to be primarily

controlled by physical processes (dispersion and dilution) and not by

bioabsorption;

the spatial extent of dissolved nutrients (those that are immediately bioavailable to

algae) will be similar to that of other dissolved constituents of the discharge (but

may differ to a degree from that of particulate material);

algal growth near the surface represents at least an intermediate term (ca. days to

weeks) response to average nutrient concentrations;

toxic effects of the discharge do not completely override the stimulus for algal

growth provided by enhanced nutrient concentrations;

other habitat conditions (flow rates, water colour etc.) are reasonably consistent

between sampling sites;

lake levels have been reasonably stable, or declining slowly, prior to sampling;

individual samples consist of sufficient sampled area to account for small scale

variability in algal biomass.

Benthic macroinvertebrates can be sampled from the lake’s shore-zone. Their assemblage

composition, diversity and abundance may reflect the effect of a discharge if it is toxic

and/or the discharge supplements or changes the nutrient and trophic status of the

receiving environment. If the former dominates, a decline in diversity and abundance,

accompanied by a change in assemblage composition, would be expected. If the latter

dominates, an increase in diversity and abundance, probably involving dominance of

particular taxa, would be expected.

Changes in benthic macroinvertebrates can be used as an indicator of the extent of any

effects from both the current Bobadil discharges and the proposed WWTP discharge on

the assumption that:

benthic macroinvertebrate abundance and/or diversity growth near the

surface/shore represents at least an intermediate term (ca. days to weeks) response

to average water quality concentrations;

toxic and/or high nutrient/algal effects of the discharge influence benthic

macroinvertebrates survival and/or growth;


other habitat conditions are reasonably consistent between the sampling sites, and

that there is no strong local gradient in assemblage composition with distance

from the Bastyan dam;

lake levels have been reasonably stable, or declining slowly, prior to sampling;

individual samples are collected from sufficient shore area at each location to

account for small scale variability in macroinvertebrate distribution.

Stitt River

The Stitt River is in a degraded ecological condition with reduced abundances and

diversity of macroinvertebrates and fish in its lower reaches (Davies et al. 2005a, b;

2006a, b; 2007 – 2012). This degraded condition is driven by poor water quality related

to discharge and seepage of low pH, high metal content waters related to current and

historical mining in the Stitt catchment. The river receives contaminated stormwater,

groundwater and seepage from historical mine-waste. In addition, Bull dam also

discharges sewage directly to the middle Stitt River by occasional spill as well as by

leakage at the dam wall base.

Faunal sampling in the Stitt River is routinely conducted using established sampling

methods for macroinvertebrates, fish and habitat. The river monitoring follows the

protocol developed by Davies et al. (2004), with sampling of instream fauna at a number

of sites in the Stitt River both upstream and downstream of pollution sources.

Sampling in autumn 2013 for TasWater in the lower Stitt River was conducted both

upstream and downstream of the proposed Tas Water WWTP discharge point, while

sampling in Lake Pieman was conducted upstream of, downstream of and within the

mouth of the Stitt River junction embayment in Lake Pieman. In both situations, all sites

are likely to be affected by the ongoing effects of mine-related discharges. Hence any

future impact caused by the proposed WWTP will be within the context of effects of the

ongoing mining-related changes in water and sediment quality.


2. Methods

2.1 Field sampling – Stitt River

A survey was conducted of benthic macroinvertebrates, fish, algae and moss in the Stitt

River, at:

1. Three MMG sites in the mid to lower Stitt River, located:

downstream of the outflow of the wetlands associated with 2 & 5 Dam (Bull

Lagoon) (site S3);

adjacent to the Rosebery sports ground (S4);

immediately upstream of Stitt Falls (S5), and of the TasWater WWTP

discharge point.

2. One TasWater site (S6) downstream of Stitt Falls, and of the proposed TasWater

WWTP discharge point.

3. Four reference (‘control’) sites:

three in the Stitt River upstream of the Bull Lagoon outflow (sites S0, S1 and

S2); and

one on an adjacent river system unaffected by any mine or town drainage

impacts (the Sterling River, site STR1).

Site details are provided in Table 1, and locations shown in Figure 1.

Sampling was conducted between 22 and 23 April 2013.

2.1.1 Benthic Macroinvertebrates

At each site, two types of sampling was conducted for benthic macroinvertebrate –

quantitative (surber) sampling, and semi-quantitative AUSRIVAS sampling. These

methods give different types of information. Surber sampling provides a strictly

quantitative assessment of diversity, abundance and community composition for formal

comparison of changes with time and differences between sites. AUSRIVAS sampling

provides indices of difference in community composition from an ‘expected’ fauna under

undisturbed ‘reference’ conditions. The quantitative method is preferred for detailed

assessment, while the latter places the condition of benthic macroinvertebrate

assemblages in a regional or statewide context.

The two sampling methods were conducted as follows:

Quantitative sampling: benthic macroinvertebrates were quantitatively sampled in riffle

habitats, by taking 10 ‘surber’ samples of the benthos, by hand disturbance of the stream

bed to a maximum depth of 10 cm into the substrate within a 30 x 30 cm quadrat

immediately upstream of a 500 micron mesh net surber sampler. The 10 sample units

were pooled at each site to provide a single composite sample, which was preserved in

neutral buffered formalin (10%) prior to processing in the laboratory. Samples were

subsequently elutriated with saturated calcium chloride solution, and the floated material

(eluant) was separated. The remaining residue and the eluant were both hand sorted, and

all animals preserved in 90% ethanol prior to identification and counting under

magnification.


AUSRIVAS sampling: rapid assessment protocol (RAP) sampling of benthic

macroinvertebrates was conducted using the standard Tasmanian AUSRIVAS sampling

protocol, separately in both riffle and edge habitats. Sampling was conducted by

disturbing the stream substrate immediately upstream of a 250 micron mesh kick net,

over a total length of 10 m of riffle or edge habitat. Samples were live-picked on site

using the standard Tasmanian AUSRIVAS protocol, with picking for 45 min, maximizing

the diversity in the picked sample of animals present in the kick net sample, while also

preserving the relative abundance of the dominant taxa.

All quantitative and AUSRIVAS macroinvertebrate samples were identified and counted

at the family level of taxonomic resolution.

2.1.2 Vertebrates

Platypus and crayfish: systematic visual searching was conducted for evidence of

crayfish and/or platypus.

2.1.3 Environmental variables

A number of environmental variables were also measured at each site for use in

bioassessment and analysis of relationships with the biota. These include % area of the

study reach as riffle, run, pool and snag mesohabitats and of stream substrates (boulder,

cobble, gravel, sand, silt and bedrock), as well as % cover of silts, moss, algae, and

organic detritus, conductivity, temperature, channel gradient and dimensions, and ratings

for bank erosion, and riparian, aquatic and trailing vegetation density.


Table 1. Details of stream study sites sampled for macroinvertebrates in the catchments of the Stitt and Sterling Rivers. See Figure 1 for map.

Site S6 is the new TasWater site. All other sites were established for the MMG monitoring program.

River or Creek

Site Code

Description Easting (GDA 1994)

Northing (GDA 1994)

Distance from

source (km)

Catchment area (km

2)

Altitude (m)

Sterling River STR1 Murchison Hway 384453 5374898 5.5 16.6 170

Stitt River S0 at top bridge 379451 5371735 5.2 19.8 190

S1 u/s Mountain Ck 379687 5372833 6.8 33.0 145

S2 u/s tailings 379387 5373173 7.3 35.9 140

S3 d/s tailings 379072 5373181 7.6 36.5 137

S4 Sports Gd footbridge 378287 5373533 8.6 36.7 128

S5 road bridge 378187 5373871 9 37 120

S6 d/s Stitt Falls bridge 378012 5373883 9.2 39.9 101

NB ‘Distance from source’ is stream length measured on 1:25,000 map from the head of the

stream drainage.

2.2 Field sampling – Lake Pieman

Benthic macroinvertebrates and benthic algae are collected from the shoreline at 15

MMG sites along the eastern side of the upper Lake Pieman reach upstream and

downstream of the Bobadil discharge point. Three new TasWater sites were established

in 2013 downstream of the MMG sites – one upstream, one downstream and one within

the Stitt River junction arm. Site locations are listed in Table 2 and shown in Figure 2.

Sampling was conducted as follows:

2.2.1 Snag algae

A fixed-area benthic pad scourer (Davies and Gee 1993) was used to sample benthic

algae on snag surfaces, with five sample units taken per location within 30 – 50 cm of the

water surface. Individual sample units were analysed for total chlorophyll-a (by a

modified acetone extraction-spectrophotometric method - APHA 1993). We calculated

mean total chlorophyll-a, corrected for phaeophytin, as a surrogate for algal biomass.


2.2.2 Shore-dwelling benthic invertebrates

Sampling was conducted by kick and sweep net sampling with a standard kick net (250

micron mesh) along a 10 m section of shoreline, with one sample collected per site. The

resulting material was preserved in formalin.

All macroinvertebrate sample material was floated in a saturated calcium chloride

solution, with hand-sorting of the residue. The floated material was then sub-sampled to

20% using the Marchant box-sub-sampler (Marchant 1989). The sub-sample was hand-

sorted under magnification. All fauna were counted and identified to family level, with

the exception of Nematodes, Oligochaetes, Copepoda, Turbellaria, and Acarina which

were not resolved to lower taxonomic levels.

Table 2. Sampling site locations in Lake Pieman. See Figure 2 for map.

Sites 1 to 15 = MMG sites; sites 16 – 18 = TasWater sites. Light grey = location of MMG’s Bobadil discharge to L Pieman; Dark grey = location of Stitt R discharge. Water conductivity at the time of sampling also shown (in micro Siemens/cm).

Site Easting

(GDA 1994) Northing

(GDA 1994) Conductivity

1 376914 5377951 36.0

2 376744 5377727 36.0

3 375237 5377539 35.8

4 376229 5376187 43.5

5 376299 5376097 46.0

6 376396 5376081 38.8

7 376457 5376035 367.0

8 376491 5376003 119.6

9 376535 5375973 73.3

10 376593 5375947 59.0

11 376710 5375746 40.2

12 376765 5375672 39.6

13 376862 5375437 38.9

14 377004 5375113 39.2

15 377197 5374778 38.5

16 377183 5374033 38.9

17 377324 5373793 38.8

18 377142 5373406 39.4


500m

N

S1

S2S3

S4

S5

Main mine site

Bull Lake

Lagoons

Lagoon

Outflow

Mountain

Ck

Stitt

River

To Lake Pieman Stitt

Falls

500m

NN

S1

S2S3

S4

S5

Main mine site

Bull Lake

Lagoons

Lagoon

Outflow

Mountain

Ck

Stitt

River

To Lake Pieman Stitt

Falls

S0

S6

Figure 1. Map of study sites in the Stitt River catchment.

Note new TasWater monitoring site (S6) added in autumn 2013.


1

2

3

4 5

6

78

910

11 12

13

14

15

16

17

18

Figure 2. Location of sampling sites in Lake Pieman.

Black arrows indicate location of discharges for MMG at Bobadil (northern arrow) and the proposed TasWater WWTP (southern arrow). Sites 1-15 are MMG monitroing sites; sites 16-18 are TasWater sites.

1:25000 map scale, grid squares = 1 km2.


2.3 Data analysis

Macroinvertebrate sample data were analysed to measures of abundance, community

composition and diversity (taxon richness). Taxon richness (number of families) was

derived from each sample. Total abundance data was derived from quantitative samples

only.

AUSRIVAS analysis

All autumn season macroinvertebrate RAP data from the stream sites are entered into the

relevant Tasmanian AUSRIVAS (Australian River Invertebrate Assessment Scheme)

model to derive O/E (observed over expected) scores. O/E scores are derived for data

converted to rank abundance based categories, allowing deviations from reference

condition to be quantified based on changes in ranked relative abundance of taxa within

the sample.

Multivariate analysis

Macroinvertebrate compositional data for all sites was used to derive a similarity matrix

using the Bray-Curtis distance measure, after fourth-root transformation of within-sample

abundances for the autumn season RAP samples (derived by combining riffle and edge

sample data). This measure is used to represent a compositional similarity between

samples, with large values (approaching 100%) representing high similarity (many taxa

in common and with similar relative abundances), and small values (approaching 0%)

representing very low similarity with few taxa in common. This matrix was then

converted into a dimensionless ‘map’ of the similarity of sites surveyed, using the MDS

ordination routine in the Primer-6 software package. This ordination provides a visual

representation of which samples (sites) are most similar and which are dissimilar, with

distances being proportional to the Bray-Curtis similarities, and reveals any disturbance

‘gradients’ in the data or consistent differences in composition between years.


3. Results: Stitt River

The composition of the macroinvertebrate fauna derived from rapid assessment

(AUSRIVAS) sampling in autumn 2013 is shown for riffle and edge habitats in Tables 3

and 4. Data from quantitative (surber) sampling is shown in Table 5.

3.1 Macroinvertebrates

Reference sites:

The fauna of the reference sites in the Sterling (STR1) and upper Stitt River (S0, S1, S2)

sites in autumn 2013 was relatively abundant and diverse, with overall means of 17.5 and

25.5 family–level taxa collected in the AUSRIVAS and quantitative riffle samples

(Tables 3 and 5). A mean of 9.3 families was collected from these sites from edge habitat

AUSRIVAS samples (Table 4).

A mean abundance of 302 individuals per sample was observed in reference site riffle

habitat quantitative samples. This equates to a density of 1697 individuals per square

meter of stream bed – similar to those observed in previous years (e.g. 1611 individuals

per square meter in autumn 2012).

The reference site fauna is dominated by Leptophlebiid mayflies, worms, chironomid

midges, worms, Grypopterygid stoneflies, elmid beetles and hydrobiosid caddis larvae in

riffle habitats (Tables 3 and 5). This ‘clean water’ fauna has remained broadly consistent

in composition since 2004. Several of these groups are sensitive to metals and acid mine

drainage, and are generally absent or severely depressed in abundance when exposed to

pollutants.

Downstream sites:

Plots of the number of taxa for each sampling site are shown in Figure 3 for quantitative

data. Diversity declined downstream from sites S2 to S5 and S6 in quantitative samples

(Figure 3).

Total abundance in quantitative samples was substantially lower at sites S3 to S5 and S6

(Figure 3) relative to reference sites. Abundances of the sensitive taxonomic groups

Leptophlebiidae and Elmidae were moderate to high at Stitt reference sites and declined

markedly in abundance at the most downstream sites (Figure 4, Table 4).

The 2013 autumn O/Erk values for the reference sites S0, S1 and S2 fell within band A

(‘equivalent to reference’), as did sites S3 and S5. O/Erk declined downstream at sites S4

and S6 (Figure 5, Table 6).

O/Erk scores indicate that sites S4 and S6 showed a significant degree of impairment

through changes in relative abundance and loss of macroinvertebrate families (Table 6).


Table 3. Macroinvertebrate data from RAP (AUSRIVAS) sampling of riffle habitats in the Ring, Stitt and Sterling River catchments, autumn 2013. O/Erk values also shown.

Riffle Stream: Sterling River Stitt River

Site: STR1 S0 S1 S2 S3 S4 S5 S6

Murchison Hway at top bridgeu/s Mountain

Cku/s tailings d/s tailings footbridge road bridge d/s Falls

Date: 24/04/13 25/04/12 23/04/13 23/04/13 25/04/13 23/04/13 22/04/13 23/04/13

Class Order Family

Annelida Oligochaeta 5 4 13 11 4 84 5 29

Arachnida Acarina 7 1 2 7 2 2 5

Crustacea Amphipoda Paramelitidae 7 4 9 20 5

Insecta Plecoptera Eustheniidae 1 7 4 5 1

Austroperlidae 2 2 1 2 2

Gripopterygidae 13 23 3 2 10 8 4

Notonemouridae 1 1 11

Ephemeroptera Leptophlebiidae 52 61 9 22 48 39 4 2

Baetidae 4 39 3 2 16

Odonata Telephlebiidae 1 4 1

Diptera Chironomidae:

subfam. Chironominae 6 4 2 3 1 4

subfam. Orthocladiinae 2 7

subfam. Podonominae 16 1 6 8 2

Simuliidae 1 1 2 4

Tipulidae 2 2 1 1 4

Athericidae 1 1 3 4

Ceratopogonidae 1

Dip. Unid. Pup. 2 1

Trichoptera Conoesucidae 1 5 1 2

Glossosomatidae 1

Hydrobiosidae 17 12 12 14 23 4 26 2

Hydropsychidae 5 2 2

Hydroptilidae 2

Leptoceridae 16 1 4 9 1 3

Philopotamidae 2

Philorheithridae 5 3 3 2 6 2 2 2

Trich. Unid. Pup. 1 1 1 2

Coleoptera ElmidaeA 1 1 4 1

DytiscidaeA 2

ElmidaeL 1

ScirtidaeL 1 1 12 7 43

N Taxa 18 17 19 16 21 11 15 15

O/Erk 0.980 0.873 1.048 0.976 1.016 0.502 0.823 0.656

Band A A A A A B A B


Table 4. Macroinvertebrate data from RAP (AUSRIVAS) sampling of channel edge habitats in the Ring, Stitt and Sterling River catchments, autumn 2013.

Edge Stream: Sterling River Stitt River


Murchison Hwayat top

bridge

u/s

Mountain

Ck

u/s tailings d/s tailings footbridge road bridge d/s Falls

Date: 24/04/13 25/04/13 23/04/13 23/04/13 25/04/13 23/04/13 22/04/13 23/04/13

Class Order Family

Platyhelminthes Turbellaria 1

Annelida Oligochaeta 1 10 2 1 2

Hirudinea

Arachnida Acarina 2 1 1 4

Crustacea Amphipoda Paramelitidae 1 15 6 2

Insecta Plecoptera Eustheniidae 1

Gripopterygidae 1 6 2 1 1

Notonemouridae 1 5 4 1 4 21

Ephemeroptera Leptophlebiidae 10 33 4 13 33 8

Oniscigastridae 2 1 2

Baetidae 7

Hemiptera Veliidae 1 17 1

Collembola


subfam. Chironominae 1 1

subfam. Orthocladiinae 3 1

subfam. Podonominae

subfam. Tanypodinae 1

Simuliidae

Tipulidae 3 1

Athericidae 1

Dixidae

Dip. Unid. Pup. 1 1 1 3

Trichoptera Hydrobiosidae 6 1 1 1 1

Leptoceridae 4 3 4 4 5 2

Philorheithridae 2 1 2 1 27 1

Trich. Unid. Pup. 1

DytiscidaeA 1 6 1

ScirtidaeL 4 6 3

DytiscidaeL

N Taxa 7 15 6 9 9 11 11 7


Table 5. Macroinvertebrate data from quantitative (surber) sampling of channel riffle habitats and environmental

data from the Ring, Stitt and Sterling River catchments, autumn 2013. N = abundance per 0.18 m2.

Riffle Stream: Sterling River Stitt River


Murchison Hwayat top

bridge

u/s

Mountain

Ck

u/s tailings d/s tailings footbridge road bridge d/s Falls

Date: 24/04/13 25/04/13 23/04/13 23/04/13 25/04/13 23/04/13 22/04/13 23/04/13

Class Order Family

Platyhelminthes Turbellaria 1 4

Mollusca Bivalvia Sphaeriidae 1

Gastropoda Glacidorbidae 1

Annelida Oligochaeta 26 55 61 91 58 66 23 39

Arachnida Acarina 1 1 1 6 1

Crustacea Amphipoda Paramelitidae 3 8 9 15

Decapoda Parastacidae 1

Isopoda Janiridae 1 1

Insecta Plecoptera Eustheniidae 3 1

Austroperlidae 1

Gripopterygidae 14 2 12 19 2 7 1

Notonemouridae 2 1 1 1 9 2 4

Ephemeroptera Leptophlebiidae 22 66 40 257 42 14 2

Baetidae 7 22 7 12 6

Odonata Telephlebiidae 1

Collembola 1 1


subfam. Chironominae 26 25 13 23 2 2 1

subfam. Orthocladiinae 11 9 11 13 2 1 3

subfam. Podonominae 4 3 2 13 9 1 1

subfam. Tanypodinae 1 1

Simuliidae 4 6 1 1 3

Tipulidae 2 2 1 1

Athericidae 1 1 2 1

Blephariceridae 3

Ceratopogonidae 1 1

Empididae 1 3 3 2 1

Dip. Unid. Pup. 1 1 4 2 1 2

Trichoptera Calocidae 1 2

Conoesucidae 3 5 1

Ecnomidae 1

Helicophidae 1

Hydrobiosidae 5 13 10 12 7 4 5

Hydropsychidae 18 10

Hydroptilidae 16 4 4 1

Leptoceridae 2 2 14 3 2

Philorheithridae 1 3 7 14 3 2 1

Polycentropodidae 2

Trich. Unid. Pup. 1 2

Coleoptera ElmidaeA 1 2 13 3 1 7

ElmidaeL 4 6 22 15 12 1

ScirtidaeL 4 7 14 19 15 30 6

PsepheniidaeL 1 2 2 1

PsepheniidaeL 2

Total abundance 154 238 259 558 174 123 94 57

N Taxa 21 26 26 29 20 13 19 11

% Algal cover 5 5 10 20 0 5 25 15

% Moss cover 0 5 10 0 0 0 0 0

% Superficial Silt cover 0 0 0 0 0 0 20 0

Conductivity (microS/cm) 38.6 36.8 36.6 36.4 42.5 39.2 61.5 51.2

Table 6. Autumn season O/Erk scores for all sites sampled in the Stitt and Sterling River catchments in autumn of 2013. Scores derived using rank abundance data and model, respectively.

Autumn 2013

Stream Site O/Erk Band

Sterling R STR1 0.98 A

Stitt R S0 0.87 A

S1 1.05 A

S2 0.98 A

S3 1.02 A

S4 0.50 B

S5 0.82 A

S6 0.66 B

3.2 Stitt River – Habitat conditions

The three variables of interest with regard to biological impacts – conductivity, % silt and

algal cover - are plotted by site in Figure 13 for autumn 2013. Conductivity was slightly

raised at sites S5 and S6 (see Table 5). Low to moderate levels of fine overlying silt-like

material were observed at site S5. Algal cover was low to moderate at all sites, peaking at

sites S2 and S5-S6 (Figure 6).

3.3 Stitt River – Vertebrates

No platypus or crayfish were observed in the Stitt during the autumn surveys, despite

active searching.


0

200

400

600

0

10

20

30

40

STR1 S0 S1 S2 S3 S4 S5 S6

Tota

l ab

un

dan

ce (per 0

.18 m

2)N

Taxa (

per

0.1

8 m

2)

N Taxa Total Abundance

Figure 3. Trends in taxon richness (of all families) and total benthic macroinvertebrate abundance across study sites in the Stitt (S0 to S6) and Sterling (ST R1) Rivers in autumn 2013, derived from quantitative Surber sample data.

0

50

100

150

200

250

300

0

5

10

15

20

25


N

Lep

top

hle

bii

da

e (p

er 0

.18

m2)

N G

rip

op

tery

gid

ae

& E

lmid

ae

(per

0.1

8 m

2)

Site

Gripopterygidae Elmidae Leptophlebiidae

Figure 4. Trends in abundance of three key habitat- and water-quality sensitive macroinvertebrate families across study sites in the Stitt (S0 to S6) and Sterling (STR1) Rivers, derived from Surber sample data in autumn 2013. Sites STR1, S1 and S2 are reference sites.


0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60


O/E

rk

2013 2012 2011 2010 2009 2008 2007 2006 2005 2004

X

A

B-D

Figure 5. Trends in autumn O/Erk scores for riffle macroinvertebrate

assemblages at study sites in the Stitt (S0 to S5) for 2004 - 2013. External reference site value in the Sterling (STR1) is shown for comparison. Horizontal dashed lines indicate bounds for impairment band A (‘equivalent to reference’) for the autumn riffle model. Band labels X, A, B-D) shown.

0

10

20

30

40

50

60

70


% o

r m

icro

S/c

m

Site

Conductivity % Algal cover % Silt cover

2013

Figure 6. Water column conductivity, % fine silt cover overlying the substrate and % cover of benthic algae in the Stitt River (S0-S6) and Sterling River (STR1) during autumn 2013 sampling.


4. Results Lake Pieman

4.1 Algae

Mean chlorophyll-a values for each site are shown in Table 8, and mean values are

plotted by site in Figure 7.

Visual inspection of the sites revealed, as in previous years, a marked and dense biofilm

just below the water surface to a maximum of ca. 0.5 - 1 m deep, associated with active

gas bubble production.

Chlorophyll-a values peaked just upstream of the Bobadil discharge point (Figure 7), but

similar in magnitude to those at sites 2 and 14.

The upstream reference sites 1-3 had a low overall mean of 6.70 mg chla/m2 (SD = 1.01),

and an upper 95% confidence limit of 8.71 mg chla/m2. Sites 4 to 6 had a mean

chlorophyll-a value of 4.72 and were more variable (SD = 2.11), with the mean falling

below the reference site upper 95% confidence limit.

Sites within the vicinity of the Bobadil outfall (sites 7 and 9) had very low chlorophyll

levels with a mean of 3.16 chla/m2 compared to reference (and to their 2012 mean of 32.2

chla/m2), with values peaking at 8.06 chla/m

2 at site 7.

Sites 11-15 further downstream, had chlorophyll levels similar to reference, with a mean

of 3.51 mg chla/m2, while the TasWater sites 16-18 had a collective mean value of 2.69

mg chla/m2.

These chl-a results indicate that TasWater sites 16 to 18 did not have enhanced benthic

algal biomass, implying a minimal impact of current Stitt River discharge nutrient levels

on local lake algal production.


Table 8. Mean chlorophyll-a values (as mg/m2) for snag surfaces in Lake Pieman (mean of 5

measurements) in autumn 2013. Shading indicates sites adjacent to Bobadil discharge (light grey) and Stitt R discharge to Lake Pieman (dark grey).

Location 2013

1 6.32

2 7.84

3 5.93

4 2.29

5 5.93

6 5.93

7 8.06

8 2.99

9 1.20

10 0.98

11 2.07

12 4.46

13 2.34

14 7.02

15 1.63

16 2.01

17 3.48

18 2.56

0

2

4

6

8

10

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Mea

n B

enth

ic c

hlo

rop

hy

ll-a

Site

Autumn 2013

Figure 7. Distribution of mean chlorophyll-a on snag surfaces in Lake Pieman in autumn (April) 2012, as means of 5 measurements, for each shore site. Arrows indicate locations of Bobadil discharge (grey) and Stitt discharge (black). Values for the three upstream reference sites are shown separately at left.


4.2 Macroinvertebrates

Samples of macroinvertebrates collected from the lake shoreline again contained

substantial numbers of benthic animals and were dominated by Leptocerid caddis larvae,

nematodes and midges (Chironomids) (Table 9).

The total diversity of truly benthic aquatic taxa from all 18 MMG and TasWater shore

sites was moderate at 26 taxa, and fell within the range observed in previous MMG

surveys.

The three TasWater sites contained a total of 24 of these 26 taxa, and were similar only to

the reference sites 2 and 3 in having the most diverse and abundant macroinvertebrate

fauna.

Spatial patterns in macroinvertebrate diversity (number of taxa) and abundance are shown

in Figure 8, for benthic taxa only (taxa living in the water column or on the surface are

ignored in this analysis, as they are highly mobile and not necessarily associated with the

sites sampled).

The upstream reference site samples (sites 1 to 3) had low diversity (mean of 9.0 taxa per

site) and were dominated by worms, and the larvae of midges and Leptocerid caddis

(Table 9).

Samples from TasWater sites (16 – 18) had a mean taxon richness of 13 taxa per site, and

were dominated by the same taxa. Taxon richness peaked at site 17 (the Stitt River

discharge site), and total abundance also showed a local peak at the same site (Figure 8).

The bulk of the peak in abundance in the vicinity of the Stitt River discharge was due to

peaks in abundance of midges (Chironomids) and freshwater worms (Oligochaetae), (see

Figure 9), indicating that these sites were most likely responding to organic nutrient

enrichment.

A similarity in community composition between TasWater sites 16 to 18 and the

reference sites is also shown in the ordination plot (Figure 10), where these sites are

loosely grouped and distinct from the remaining MMG monitoring sites. It is noteable

that sites 17 (Stitt River discharge) and 8 (Bobadil discharge) lie at either end of the site

distribution in this ordination plot, characterised by a shift from high to low abundance

and diversity.

Overall, it appears that sites 17 to 18 have the highest macroinvertebrate diversity and

abundance overall, are most closely related to the reference sites in composition, while

also showing a small response to organic enrichment in the form of greater diversity

combined with enhanced midge and worm abundances.


Table 9. Macroinvertebrate data from eastern shore zone sampling sites in upper Lake Pieman in autumn (April) 2011. Abundances are n

per 20% of 10 m kick sample (approx. n per 0.6 m2 shoreline habitat).

24-Apr-13 Site: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Class Order Family

Bobadil outfall

u/s Stitt R Stitt Bay d/s Stitt R

Platyhelminthes Turbellaria 1 1 1 1 1 2 7

Nematoda

1 5 136 1 3 2 1

9 2 2

11

1

Mollusca Bivalvia Sphaeriidae 3 3

1

11 4

2

Annelida Oligochaeta

2 1

4 9 9 4 1 1 6 1 2 5 6 1 18 7 32

Crustacea Amphipoda Paramelitidae

1

Copepoda

3 1

1

1 2 3 4

Ostracoda

27 2 2 5 1 19 5 2 9

1

3

Insecta Plecoptera Gripopterygidae 1

1

1

1

1 1 1 4

Notonemouridae

1

2

Ephemeroptera Leptophlebiidae

7

10

Odonata Hemicorduliidae

1

Hemiptera Veliidae

4

2

1

Corixidae 1 8 2 1 2

1 3 11 5

3 6 1 1


Subfam. Chironominae 3 14 5

3

4

1 1

1 3 2 21 2

Subfam. Orthocladiinae

1

1

1 2

Subfam. Tanypodinae 1 15 5 4 20 8 2 4 1 4 3 3 8 12 1 3 70 20

Ceratopogonidae 2

1

2

2

Dip. Unid. Pup. 2 1

1

Trichoptera Atriplectididae

2

1 2

1 1 1

1

1 9

Calocidae

1

Ecnomidae 8

5

1

2 3 1 4 2 9

Hydroptilidae

1

Leptoceridae 30 14 11 7 5 36 16 3 36 22 4 14 12 13 35 23 30

Philorheithridae

1

Polycentropodidae

1 1

Coleoptera DytiscidaeA 1 1 1 1 4 1 1 2

Total Abundance 13 116 175 24 58 30 75 32 30 65 33 14 50 50 17 83 153 121

N Taxa 9 11 14 7 12 9 9 8 8 9 9 6 9 9 5 15 16 14

Total benthic abundance 12 78 170 21 51 29 51 24 15 51 32 10 44 48 17 80 149 114

N Benthic Taxa 8 8 11 5 10 8 6 6 5 7 8 4 8 7 5 13 14 12


0

5

10

15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

N B

enth

ic T

ax

a

Site

Autumn 2013

0

50

100

150

200

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

To

tal

Ben

thic

ab

un

da

nce

Site

Autumn 2013

Figure 8. Number and total abundance of benthic taxa per sample of lake edge habitat in Lake Pieman in autumn (April) 2013. Arrows indicate locations of Bobadil discharge (grey arrow) and Stitt River discharge (black arrow). Upstream reference site values are shown at left.


0

20

40

60

80

100

120

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

N C

hir

on

om

idae

Site

Autumn 2013

0

10

20

30

40

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

N O

ligoch

aet

ae

Site

Autumn 2013

Figure 9. Total abundance of midges (Chironomids) and freshwater worms (Oligochaetae) per sample of lake edge habitat in Lake Pieman in autumn (April) 2013. Arrows indicate locations of Bobadil discharge (grey arrow) and Stitt River discharge (black arrow). Upstream reference site values are shown at left.


Figure 10. MDS ordination of 2013 samples from 18 sites along Eastern shore of Lake Pieman. Sites 1 – 15 = MMG Bobadil outfall impact monitoring sites; sites 16 – 18 = TasWater Stitt River outfall monitoring sites. Light grey hashed ellipse = reference and TasWater site grouping; black dashed ellipse = grouping of remaining MMG sites. Bobadil and Stitt discharge sites indicated in red.


5. Overall Biological Condition

5.1 Stitt River

The lower Stitt is in poor to moderate ecological condition. A moderate degree of impact

on the biota was observed at site S3, downstream of the Bull Lagoon discharge point.

Biological condition is poor further downstream however, with sites S4, S5 and S6 being

in a severely degraded state with low to very low macroinvertebrate densities and

reduced diversity.

Site S6, downstream of the proposed TasWater WWTP, is in an overall poorer state than

sites S5 and S4 upstream, with reduced taxon richness and total abundance, a

substantially reduced number of water quality sensitive macroinvertebrate taxa (caddis,

Leptophlebiid mayflies, beetle larvae) and greater densities of organic-tolerant worms.

It is apparent that site S6 is also suffering from the effects of mine-water related pollution.

The impact of sewage discharge from Bull Lagoon, observable at site S3, is not a major

contributor to biological decline in the lower reaches of the Stitt where biological

condition appears to be largely dictated by historical mining-related declines in water

quality.

Despite these effects, there is a still just a sufficient fauna at both sites S5 and S6 to act as

a basis for future monitoring and detection of any potential impact from the proposed

WWTP discharge.

5.2 Lake Pieman

Overall, it appears that the shoreline of Lake Pieman showed no substantive algal

response to the existing inflow of the Stitt River discharge in autumn 2013, with algal

levels falling well below the upper limit derived from reference site values.

By contrast, the benthic macroinvertebrate response was marked, with substantially

higher total abundance and taxon richness at all three TasWater sites (peaking at site 17).

This response, combined with the relatively high abundances of Chironomids and

freshwater worms, suggests a minor positive supplementation effect of the Stitt river

inflow on the Lake Pieman shoreline fauna. This suggests a stimulatory effect of

enhanced organic/nutrient levels on the near-shore fauna of the lake within the vicinity of

the Stitt inflow.

The observed biological patterns around the Stitt discharge area in Lake Pieman are

currently not of major ecological significance.

We have identified that there is both sufficient benthic fauna and algal biomass to allow

future detection of any effect from the proposed WWTP discharge to the Stitt River on

the lake shore ecosystem.


6. References

APHA 1993. Standard Methods for Water and Wastewater Analysis. APHA-AWWA, Vol. 19.,

Princetown USA.

Bowling LC, Steane MS and Tyler PA 1986. The spectral distribution and attenuation of

underwater irradiance in Tasmanian inland waters. Freshwat. Biol. 16:313-335.

Davies AL and Gee JHR 1993. A simple periphyton sampler for algal biomass estimates in

streams. Freshwat. Biol. 30, 47-51.

Davies PE and Cook LSJ 2002. Aquatic bioassessment of the Savage River catchment. 2001

Survey report. SRRP Project 038. Final Report to DPIWE, January 2002. 55 pp.

Davies PE and Cook LSJ 2013. Biological Condition of the Ring and Stitt Rivers: Survey of

aquatic biota, Spring 2012 and Autumn 2013. Final Report to MMG, Rosebery, 33 pp.

Davies PE, Cook LSJ and Sloane T 2004. Biological Condition of the Ring and Stitt Rivers:

Survey of fish and macroinvertebrates, 2003/04. Final Report to Pasminco, 37 pp.

Davies PE, Cook LSJ and Sloane T 2005. Definition of Bobadil discharge mixing zone in Lake

Pieman by in-lake biological sampling. Report to Zinifex Pty Ltd, Rosebery Mine. March

2005. 22 pp.

Davies PE, Cook LSJ and Sloane T 2005a. Biological Condition of the Ring and Stitt Rivers:

Survey of macroinvertebrates, autumn 2005. Final Report to Pasminco, 24 pp.

Davies PE, Cook LSJ and Sloane T 2005b. Biological Condition of the Ring and Stitt Rivers:

Survey of macroinvertebrates, spring 2005. Final Report to Pasminco, 16 pp.

Davies PE, Mitchell N and Barmuta LE 1996. The impact of historical mining operations at

Mount Lyell on the water quality and biological health of the King and Queen River

catchments, western Tasmania, Mount Lyell Remediation R&D Program, Supervising

Scientist Report 118, Office of the Supervising Scientist, Barton ACT.

Marchant R 1989. A subsampler for samples of benthic invertebrates. Aust. Soc. Limnol. Bull. 12,

49-52.

Documents

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