GEOGRAPHICAL DISTRIBUTION SALT MARSHES - UC Davis: Environmental
Transcript of GEOGRAPHICAL DISTRIBUTION SALT MARSHES - UC Davis: Environmental
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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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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):