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SALT MARSHES

- areas vegetated by herbs, grasses or low shrubs bordering saline water bodies

- interface between terrestrial and marine habitats

- tidal submergence

GEOGRAPHICAL DISTRIBUTION

Arctic marshes

Boreal marshes

Temperate marshes

Tropical marshes

Inland salt marshes

ARCTIC MARSHES- Spitzbergen, Greenland, Canadian Arctic, Alaskan marshes, - ice action, patchy distribution grasses, sedges, bryophytes, very few annuals (Carex subspathacea; Puccinellia phryganodes)

BOREAL MARSHES - ecotone between arctic and temperate

- Hudson Bay, British Columbia, Northern Baltic, Southern Norway and Sweden

- more plant species (arrow weed, Triglochin maritima, pickleweed Salicornia europea)

- low salinities – (melt water)

TEMPERATE MARSHES- East and West coast of the U.S., Europe, Japan, China, Korea, A ustralia, South Africa “Dry coast type – Mediterranean marshes”

- greater floristic differentiation, graminoids, halophytes, less mosses

TROPICAL MARSHES - adjacent to mangroves,

- secondary communities in disturbed mangroves

- species poor

INLAND SALT MARSHES-white alkali soils ("solontschak"), semi-arid areas (Caspian Sea, Middle east, Utah)

- black alkali soils ("solonetz")

- no tidal influence

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Sesuvium portulacastrum

Booby, Sula sp.

TROPICAL MARSHESGEOMORPHOLOGY

- marsh development determined by tides, shoreline structure, freshwater input, sedimentation, primary production

- shoreline features allowing for marsh development, barrier islands

-marsh stability - determined by relative rates of sedimentation

salt marshes young (~ 3000-4000 y)

-coastal submergence (cold periods global lowering of sea level by

100-150 m; 15000-6000 y ago rapid sea level rise; last ~ 5000 y

relatively stable rise of about 1m/century)

Gulf Coast: 1.2 cm/y submergence,only 0.7cm/y accretion; West coast about equal

HYDROLOGY - lower and upper limits of the marsh - tidal range

- upper marsh (high marsh) flooded irregularly, higher differences in salinity

- lower marsh (intertidal marsh) flooded almost daily

-tidal creeks - conduits for material and energy (1st, 2nd, 3rd, order –shift, 4th, 5 th order stable )

role of vegetation in trapping the sediments progression x retrogression

- tidal pools (ponds) and pans - elevated salinitypool origin: patchy distribution of vegetation, accretion

remaining open parts of retrogressing creeks

CHEMISTRY

- water and soil salinity influenced by: frequency of tidal inundation , rainfall; network of tidal creeks

- nutrients - often N-limited, usually not P-limited

-high sulfur concentrations, sulfide toxicity

Salinity dominated by NaCl mg/l mg/l

Average sea water composition: Cl 19.4 Na 10.8

SO4 2.7 Mg 1.3

Sum = 35 g/l = 35 ppt Ca 0.4

K 0.4

Salinity data can be expressed as specific conductivity (conductance).

Conductivity [mS/cm] = 1.5 * Salinity [ppt]

tidal submergence

STRESS

- tidal submergence

- salinity

- anoxia

- temperature

- litter accumulation ( “wrack”)

- human activities

VEGETATION STRUCTURE

- perennial grasses (cordgrass)

- Spartina anglica (England)

- Spartina alterniflora(East Coast)

- Spartina foliosa (West Coast)

- Distichlis spicata – salt grass

- succulent species

-Salicorniaspp., Jaumea, Batis

- algae, seaweeds

- shrubs Grindelia

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Spartina foliosa Distichlis spicata – salt grass

Salicornia virginica

Parasitic plant –dodder Cuscuta salina

Plant zonation

algae, seaweedsGrindelia sp.

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Spartina stories

(1)

1829 – S. alterniflora (native of the East Coast) introduced to England

Native S. maritima x S. alterniflora

2n = 60 2n = 62

S. townsendii (~ 1870) sterile hybrid

2n = 62

S. anglica

2n = 120, 122, 124 (fertile allopolyploid)

S. anglica completely altered the saltmarsh ecology of N-European marshes

Spartina stories

(2)

1960’s – S. alterniflora introduced to the West coast

Native S. foliosa x S. alterniflora

hybrid

Hybrids are more aggressive, they are altering the ecology of the West coast marshes

(3)

S. anglica introduced to China and New Zealand – extremely invasive

Hybrid swarms

Spartina has not been a successful colonizer in the tropical regions – requires cold periods for seed germination

C4 plant

Growth of Spartina alterniflorais strongly regulated by sediment oxidation status – tall plants (~ 3 m!) near the water edge and along the tidal creeks; in low redox zones very short individuals (~ 20 cm), low AEC

Spartina alterniflora - initial invasion

HALOPHYTES

(plants which complete their life cycle in saline environment)

non-halophytes ( glycophytes)

facultative and obligate (??) halophytes

The relative biomass increase can be just

caused by salt uptake

The effects of salinity:

1) direct toxic effect of Na, Cl

2) interference with uptake of essential nutrients

3) lowered external water potential

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+

-

salinity

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WATER POTENTIAL ( ? )

-halophytes attain internal water potential below that of external solution to generate turgor pressure permitting growth

- (water potential is the thermodynamic parameter – energy (work) involved in moving 1 mole of water from some point in the system into a poolof pure water)

-increase in salt concentration = decrease in ? (MPa)

H2O

salt concentration: low high

? : high low

? i = internal potential

Plants: ? i = ? p + ? ? ? p = turgor pressure

? ? = osmotic potential

WATER POTENTIAL ( ? )

? i = internal potential

Plants: ? i = ? p + ? ? ? p = turgor pressure

? ? = osmotic potential

? e = external water potential; freshwater ~ 0 MPa

? ? in the range of –0.5 to –1.0 MPa (salts in cytoplasm)

=> ? p has to be +0.5 to +1.0 MPa (for turgor pressure to stay positive)

Sea water: ? e = about –2.5 MPa

? i has to stay below ? e;

? p has to stay positive => ? ? ~ -3.5 MPa

(? ? ~ -3.5 MPa corresponds to ~ 40 ppt NaCl !)

WATER POTENTIAL ( ? )

- halophytes attain internal water potential below that of external solution to generate turgor pressure permitting growth

HOW ??

1) Uptake of inorganic salts ( salts are already there; transport mechanism – transpiration – is there)

2) Production of organic osmolytica (drain on carbohydrates and N; examples: glycinbetain, prolin, sugars

3) Dehydration

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Regulation of salt uptake:

Examples: Salicornia spp., Batis, Jaumea, Sesuvium

REGULATION OF SALT UPTAKE

- exclusion

- succulence (Salicornia spp., Batis, Jaumea, Sesuvium)

- extrusion (secretion) requires energy (Distichlis, Frankenia, Limonium)

- leaf loss (Sessuvium)

- reduced transpiration, high WUE (C4)

Limonium californicum – sea lavender

ALGAL MATS

Positive plant interactions

Cyanobacteria–N2 fixation

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FAUNA

- permanent x visitors x seasonal (migrating birds)

- invertebrates: lugworms, crabs, many insects, spiders

- vertebrates: not many reptiles and amphibians, fish

- birds

- mammals: rabbits and hares, mice, muskrats, nutria

Lugworm – Arenicola marina, large annelid worm

- feeds on bacterial particles and DOM

- has to pump in water with oxygen for respiration

- can switch to anaerobic respiration, changes in AEC

- deals w. high concentrations of H2S by oxidizing it during aerobic conditions

- deals w. high salinity by having high concnetrations of salts in body cavity + some organic osmolytica

IMPACT OF GEESE ON ARCTIC AND BOREAL MARSHES

La Pérouse Bay (part of Hudson Bay)

Breeding grounds of Lesser snow geese (Chen caerulescenscaerulescens) – keystone species

~ 1.2 mil. 1970’s > 2 mil. 1990’s > 3 mil. 2000’s

end May- mid August

A – before geese increased over carrying capacity:

Geese removed about 80% of NPP (100 -200 g.m2 ~ 1-2g N/m2)

Positive feedback – more grazing => more biomass production

Input of N from droppings

After geese leave in August, plants have time to recover; open spaces dominated by cyanobacteria that contribute ~ 1g/m2 of N before the season is over)

IMPACT OF GEESE ON ARCTIC AND BOREAL MARSHES

B – after geese increased over carrying capacity:

Geese need more biomass, grubbing activities – digging for rhizomes

=> increase plant damage => bare areas => exposure of marine sediments => increased evapotranspiration => increased salinity (hypersalinity)

Larger bare areas => faster snow melt => more geese => more grubbing

Larger bare areas - problems with revegetation, grass, Puccineliaphryganodes, is not able to colonize large bare patches, Salicorniaborealis

ECOSYSTEM FUNCTIONS

Primary production - high (but not in all marshes)

Spartina alterniflora East Coast NPP 2500g/m2/year

- West Coast marshes lower production

- streamside effect

- algal production important - epibenthic algal mats

Southern California marshes: algal production about equal to vascular plant production

Decomposition - detritus broken down mostly by bacteria

- export to adjacent estuaries

Marshes of New England (from Mark Bertness web page)

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+

+

+ : feces from mussel beds increase production and stabilize the marsh edge; fiddler crabs aerate; dense vegetation aerates; dense vegetation prevents hypersalinization

- : intraspecific competition – displacing subordinates by stronger competitors

ANOXIA HYPERSALINITY

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--

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POSITIVE INTERACTIONS – prevalent under harsh physical or limiting nutrient conditions; (Mark Bertness et al)

PNAS 99:1395, 2002

Control of plant growth:

BOTTOM UP X TOP DOWN

Resource availability Consumers

(nutrients) (predators

herbivores

primary producers)

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Bottom-up forces have been regarded as primary determinants of plant production in Spartina alterniflora dominated salt marshes on the Atlantic coast (Odum, Mitsch & Gosselink)

Never tested experimentally !!

Marshes on Sapelo Island, Georgia

Periwinkle story(Silliman & Bertness 2002, PNAS 99: 10500)

- prosobranchperiwinkle snails (Littorariairrorata) are common inhabitants of the East coast salt marshes

- these snails are consumed by predators such as the blue crab (Calinectessapidus)

- it has been assumed that periwinkle snails feed only on dead and dying Spartina plant materials

- Silliman and Bertness found that once periwinkles are released from the predation by crabs, they will readily eat living cordgrass.

- also, the greater the nitrogen content of the grass the more attractive the grass became to the periwinkles

- nitrogen is the prime nutrient in mainland run-off

TROPHIC CASCADE

I SPARTINA

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Low periwinkle density plot

High periwinkle density plot

tissue scarring - radulation

-the results indicate that a simple trophic cascade regulates the structure and functions of the salt marshes

- the discovery of this simple trophiccascade implies that over -harvesting of snail predators, such as blue crabs, may be an important factor contributing to the massive die- off of salt marshes across the southeastern United States

- densities of blue crabs dropped 40-80% in the Gulf estuaries over last 10 years

- predator depletion can result in in conversion of salt marshes to mud flats.

Human impact – restoration projectsTIDAL FRESHWATER MARSHES (TFM)- historically ignored

- marshes that are close enough to coast to experience significant tides, but above the reach of salt water

Geographical Distribution

- distributed worldwide, usually in association with large river systems, deltas, “sloughs”

Geomorphology- recent in origin, in river valleys created during the Pleistocene period of low sea levels

Salinity- TFM occur where the average annual salinity is below 0.5 ppt

- salinity may rise periodically during droughts; inflow of salt water during hurricanes

Tidal range- sometimes the tidal range of TFM can exceed that of tidal salt marsh due to the constricting of the tidal mass as it moves upstream in a narrowing river channel

Sediment composition and bank morphology- usually fine inorganic and organic sediments, sometimes more erodable than salt marsh sediments

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Chemistry

- not too high sulfur concentrations

- more dissolved and particular organic carbon than salt marshes, more C input of terrestrial origin

- lot of nitrogen bound in organic form

- variable phosphorus

Vegetation structure- plant species restricted to freshwater or low salinities

- usually complex assemblages of perennial and annual species

- large proportion of broadleaved emergent macrophytes (Pontederia, Sagittaria)

- many submersed species (Potamogeton spp., Myriophyllum spp., Elodea spp.) in ponds and creeks

- communities of annuals (Bidens spp., Polygonum spp. )

- often extensive stands of Typha spp., Zizannia aquatica, Panicumhemitomon “floating marshes”

- large seed banks, germination dependent on flooding

- no distinct zonation because of habitat overlap

- benthic algae, usually during the fall and winter when the vascular flora is reduced

Fauna- relatively low species diversity of invertebrates

- much higher diversity of reptiles and amphibians than in salt marshes

-largest and most diverse populations of birds of any wetland type

- mammals: otter, mink, muskrat, nutria, raccoon, marsh rice rat

Ecosystem function- Primary production - higher than in salt marshes (range of 1000 to 3000 g/m2/y)

-Decomposition - generally proceeds at a rapid rate

- much higher methane emissions in TFM than in salt marshes

-Nutrient flux - nutrient transformers

Human impact – ex. Danube delta

DANUBE DELTA – concept of hydrologic connectivity

Water mediated transfer of matter, energy, and/or organisms

Alterations of HC are threatening biological reserves

Pringle 2001, Ecol. Appl . 11: 981

DANUBE DELTA(Pringle et al. 1993 Amer. Sci., Vol. 81)

-the largest European wetland (Romania & Ukraine)

- consists of rivers, lakes,marshes, meadows, sand dunes and forests

- the delta receives drainage from70% of the area of central Europe => major environmental problems

- rich economic resource of fish, timber and reed and is home to about 80 000 people

-Important migrating bird habitat

Die-offs of reeds

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- as a centre of wetland biodiversity, the Danube delta ranks among the top sites in Europe.

-up to 75 different species of fish can be found in the delta and several globally threatened bird species, including the red -breasted goose, the Dalmatian pelican and the pygmy cormorant, either breed in the delta or use the delta as a winter quarter.

- impacts: hydrology changes upstream AND in the delta; pollution (Hg)

-creation of a canal network in the delta

- the reduction of the wetland area by the construction of agricultural polders and fishponds.

-As a result, biodiversity has been reduced and the fundamentally important natural water and sediment transport system has been altered, diminishing the ability of the delta to retain nutrients.

Danube Delta

- pollution – high nutrient loads in the Danube river from upstream

- changes in hydrology - elimination of natural water flow

- floodplain elimination; coastal erosion (17 m/y!)

- attempts to drain for agriculture failed

- aquaculture – reduced local fisheries

corn

reed

Failed aquaculture operation

- diked polders for Phragmites cultivation- decline in reed growth, replacement with cattails- overall decrease in species diversity- contamination with pesticides and heavy metals

- decline in emergent macrophytes- algal blooms (Cyanobacteria )- Black sea = one of the largest anoxic marine basins in the world

- 1990’s – political changes in Romania

- August 1990 – Biospheric reserve & World Heritage Site

(about 7000 sq. km – not ALL is damaged!)

-needs integrated watershed management and international cooperation !!

- specifically water quality improvement and restoration of the natural flow – hydrologic connectivity

- Danube Delta Biodiversity project

- Partners for Wetlands Ukraine is now developing wetland restoration sites in the Danube Delta floodplain

- WWF project

- Black Sea Action Plan

Danube delta

Polder restoration sites

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Other threatened deltas:

Colorado River, Yellow & Huang Rivers, Ganges River

Nile, Mississippi, Niger, erosion because of the elimination of sediment input

Danube Delta - >300 lakes of various types (reference sites):