GEOGRAPHICAL DISTRIBUTION
SALT MARSHES - areas vegetated by herbs, grasses or low shrubs bordering saline water bodies - interface between terrestrial and marine habitats Arctic marshes
- tidal submergence
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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TROPICAL MARSHES GEOMORPHOLOGY - 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 Sesuvium portulacastrum
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 Booby, Sula sp.
HYDROLOGY - lower and upper limits of the marsh - tidal range
CHEMISTRY
- upper marsh (high marsh) flooded irregularly, higher differences in salinity
- water and soil salinity influenced by: frequency of tidal inundation , rainfall; network of tidal creeks
- lower marsh (intertidal marsh) flooded almost daily
- nutrients - often N-limited, usually not P-limited -high sulfur concentrations, sulfide toxicity
-tidal creeks - conduits for material and energy ( 1s t, 2nd, 3rd , order –shift, 4th , 5 th order
Salinity dominated by NaCl
stable )
Average sea water composition:
role of vegetation in trapping the sediments progression x retrogression
mg/l Cl SO4
- tidal pools (ponds) and pans - elevated salinity
Sum = 35 g/l = 35 ppt
pool origin: patchy distribution of vegetation, accretion
mg/l
19.4
Na
10.8
2.7
Mg
1.3
Ca
0.4
K
0.4
Salinity data can be expressed as specific conductivity (conductance). Conductivity [mS/cm] = 1.5 * Salinity [ppt]
remaining open parts of retrogressing creeks
STRESS - tidal submergence
VEGETATION STRUCTURE
- salinity
- perennial grasses (cordgrass)
- anoxia
- Spartina anglica (England)
- temperature
- Spartina alterniflora(East Coast)
- litter accumulation ( “wrack”)
- Spartina foliosa (West Coast)
- human activities
- Distichlis spicata – salt grass - succulent species
tidal submergence
-Salicorniaspp., Jaumea, Batis - algae, seaweeds - shrubs Grindelia -
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Spartina foliosa
Distichlis spicata – salt grass
Salicornia virginica
Plant zonation
Parasitic plant – dodder Cuscuta salina
algae, seaweeds
Grindelia sp.
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Spartina stories
Spartina stories
(1) 1829 – S. alterniflora ( native of the East Coast) introduced to England Native S. maritima x S. alterniflora 2n = 60
(2) 1960’s – S. alterniflora introduced to the West coast Native S. foliosa x S. alterniflora
2n = 62 S. townsendii (~ 1870) sterile hybrid 2n = 62
hybrid Hybrids are more aggressive, they are altering the ecology of the West coast marshes
S. anglica 2n = 120, 122, 124 ( fertile allopolyploid) S. anglica completely altered the saltmarsh ecology of N-European marshes
(3) S. anglica introduced to China and New Zealand – extremely invasive
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 Hybrid swarms
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
+ 0
salinity
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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WATER POTENTIAL ( ? )
WATER POTENTIAL ( ? )
? i = internal 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 pool of pure water)
-increase in salt concentration = decrease in ?
?
:
high
? ? = 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)
high
Sea water: ? e = about –2.5 MPa
low
? i = internal potential Plants: ? i = ? p + ? ?
? p = turgor pressure ? ? = osmotic potential
WATER POTENTIAL ( ? ) -
halophytes attain internal water potential below that of external solution to generate turgor pressure permitting growth
? i has to stay below ? e; ? p has to stay positive => ? ? ~ -3.5 MPa (? ? ~ -3.5 MPa corresponds to ~ 40 ppt NaCl !)
REGULATION OF SALT UPTAKE - exclusion - succulence ( Salicornia spp., Batis,
HOW ??
Jaumea, Sesuvium)
1)
Uptake of inorganic salts ( salts are already there; transport
- extrusion (secretion) requires
mechanism – transpiration – is there)
energy (Distichlis, Frankenia, Limonium)
2) 3)
? p = turgor pressure
(MPa)
H2O salt concentration: low
Plants: ? i = ? p + ? ?
Production of organic osmolytica ( drain on carbohydrates and N; examples: glycinbetain, prolin, sugars
- leaf loss ( Sessuvium)
Dehydration
- reduced transpiration, high WUE
(C4)
------Regulation of salt uptake:
Limonium californicum – sea lavender
Examples: Salicornia spp., Batis, Jaumea, Sesuvium
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
IMPACT OF GEESE ON ARCTIC AND BOREAL MARSHES
La Pérouse Bay (part of Hudson Bay)
B
Breeding grounds of Lesser snow geese (Chen caerulescens caerulescens) – keystone species ~ 1.2 mil. 1970’s
> 2 mil. 1990’s
> 3 mil. 2000’s
– 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
end May- mid August
(hypersalinity)
A
Larger bare areas => faster snow melt => more geese => more
– before geese increased over carrying capacity:
Geese removed about 80% of NPP (100 -200 g.m2 ~ 1-2g N/m2)
grubbing
Positive feedback – more grazing => more biomass production
Larger bare areas - problems with revegetation, grass, Puccinelia phryganodes, is not able to colonize large bare patches, Salicornia
Input of N from droppings
borealis
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)
ECOSYSTEM FUNCTIONS
Marshes of New England (from Mark Bertness web page)
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
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POSITIVE INTERACTIONS – prevalent under harsh physical or limiting nutrient conditions; (Mark Bertness et al)
HYPERSALINITY
ANOXIA
+
+
+
-
-
+
+ : 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
PNAS 99:1395, 2002
Marshes on Sapelo Island, Georgia
Control of plant growth: BOTTOM UP
X
TOP DOWN
Resource availability
Consumers
( nutrients)
( predators herbivores primary producers)
-------------------------------------------------------------------------------------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 !!
Periwinkle story
TROPHIC CASCADE
(Silliman & Bertness 2002, PNAS 99: 10500)
- prosobranch periwinkle snails (Littoraria irrorata) are common inhabitants of the East coast salt marshes - these snails are consumed by predators such as the blue crab (Calinectes sapidus)
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SPARTINA
- 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
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-the results indicate that a simple trophic cascade regulates the structure and functions of the salt marshes
Low periwinkle density plot
- the discovery of this simple trophic cascade 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 4080% in the Gulf estuaries over last 10 years
High periwinkle density plot
- predator depletion can result in in conversion of salt marshes to mud flats.
tissue scarring - radulation
Human impact – restoration projects
TIDAL 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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Vegetation structure
Chemistry
- plant species restricted to freshwater or low salinities
- 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
- 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
- variable phosphorus
- communities of annuals (Bidens spp., Polygonum spp. ) - often extensive stands of Typha spp., Zizannia aquatica, Panicum hemitomon “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
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
Pringle 2001, Ecol. Appl . 11: 981
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- as a centre of wetland biodiversity, the Danube delta ranks among the top sites in Europe.
Danube Delta
-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.
- changes in hydrology - elimination of natural water flow
-impacts: hydrology changes upstream AND in the delta; pollution (Hg)
- aquaculture – reduced local fisheries
- pollution – high nutrient loads in the Danube river from upstream - floodplain elimination; coastal erosion (17 m/y!) - attempts to drain for agriculture failed
-creation of a canal network in the delta - the reduction of the wetland area by the construction of agricultural polders and fishponds.
reed
-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. corn
- diked polders for Phragmites cultivation
- decline in emergent macrophytes
- decline in reed growth, replacement with cattails - overall decrease in species diversity - contamination with pesticides and heavy metals
- algal blooms (Cyanobacteria ) - Black sea = one of the largest anoxic marine basins in the world
Failed aquaculture operation
Danube delta
- 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
Polder restoration sites
- WWF project - Black Sea Action Plan
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Danube Delta - >300 lakes of various types (reference sites):
Other threatened deltas: Colorado River, Yellow & Huang Rivers, Ganges River Nile, Mississippi, Niger, erosion because of the elimination of sediment input
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