Types of Wetlands

For saltwater, coastal, and tidal wetlands the classifications marine and estuarine apply.

For freshwater wetlands, which make up 90% of wetlands, the following apply:

lacustrine = influenced by lakes

riverine = influenced by rivers

palustrine = marshy (bogs, marshes, swamps)

1. Salt Marshes

  • found worldwide at mid to high latitudes
  • tidal
  • vegetation primarily salt tolerant grasses and rushes, zoned according to tide height
  • detrital food chain is dominant
  • among the most productive ecosystems in the world
  • anaerobic decomposition is critical in recycling nutrients

Geology:

  • gently sloped and intertidal
  • can be deltas like the Mississippi or reworked marine sediments like most of the North American coastline
  • rates of erosion and deposition, tide height, frequency and volume, and seasonal variation of river flow into an area determine marsh stability, but there may also be biological factors:

1. emergent grass dampens waves, reducing energy

2. stems and leaves trap sediments

3. roots and rhizomes stabilize sediments

4. algal, bacterial, and diatom films help trap sediments

5. colonial animals influence deposition

-oysters modify water flow

-fiddler crabs enhance permeability

6. macroinvertebrates trap suspended detritus and deposit it

7. excessive grazing by waterfowl or mammals allows increased erosion

2. Tidal Freshwater Marshes

  • the edges of the Waccamaw river, for example (S.C. has the highest acreage of these on the east coast)
  • flat coastline, adequate rainfall to maintain riverflow, good tidal range
  • food chain is predominantly detrital with benthic invertebrates being a key link
  • high productivity
  • heavy use by wildlife, especially birds because of the structural diversity of the vegetation

3. Mangroves

  • replace saltmarsh as the dominant coastal ecosystem in subtropical and tropical regions worldwide
  • association of halophytic trees, shrubs, and other plants growing in brackish to saline tidal waters of tropical and subtropical coastlines
  • important in:

-exporting organic matter to adjacent coastal food chains

-providing physical stability to shorelines to prevent erosion

-protecting inland areas from storm damage

-sinks for nutrients and carbon

  • found in the U.S. only in Florida (and Puerto Rico-they're protected now in Florida)
  • important as shelter and source of food for a wide variety of animals

-invertebrates grow on prop roots

-wading birds

-important nursery areas for fish and shellfish

4. Freshwater Marshes

(Pictures are from Niering,W.A. 1997. Wetlands. New York: Alfred A. Knopf. 640 p.)

  • non-tidal, freshwater, dominated by grasses, sedges, and other emergent halophytes
  • can be small marshes up to the size of the Everglades
  • Prairie Potholes-depressions left by glaciers
  • Nebraska Sandhills-stabilized sand dune field with lowlands between dunes being wetlands
  • these are especially critical for groundwater recharge
  • marshes around the Great Lakes
  • riverine marshes
  • detrital ecosystem like the others
  • particular problems with alien species partly because they tend to be more disturbed than other wetlands and so are more susceptible

5. Northern Peatlands

  • bogs, fens, moors, muskegs, heath
  • primarily found in northern climates where there is a good amount of rain
  • pocosins are the southernmost version and 70% of those are in North Carolina
  • mosses, especially of the genus Sphagnum are the most important peat building plants in bogs
  • deficient in nutrients so primary production isn't very high
  • very acidic environment so there are few reptiles or amphibians
  • not many mammals but because these are becoming the only remaining large tracts of land (because they're impossible to build on) increasingly, the wide ranging mammals like bears, moose, and others really depend on these places

6. Southern Deepwater Swamps

  • freshwater systems with standing water for most of the year
  • common on the coastal plain of the the southeast U.S.
  • cypress and tupelo trees are typical (thus these can be economically important)
  • high organic matter combined with clay soils and constant standing water creates anaerobic conditions in the soil, acidic water
  • aboveground productivity can be very high if the water flushes with some regularity, however if it doesn't, nutrients get used up or become unavailable and productivity is lower
  • beavers, otters, minks, and raccoons are common, bobcats, deer occasionally
  • because of the relatively high acidity, amphibians and reptiles tend not to be overly abundant
  • lots of birds, both locals and migrants use these

7. Riparian Wetlands

  • influenced by an adjacent lake or river
  • interface between terrestrial and aquatic ecosystems
  • flooded at least some of the time
  • common in the southeast and western U.S.
  • generally linear open systems in that lots of energy and material passes through rather than "getting stuck"
  • connected to upstream and downstream as well as upland and aquatic ecosystems
  • tend to be highly productive because there's a frequent influx of nutrients
  • high biodiversity because of the edge effect

8. Bottomland Hardwood Forests

support large biodiversity due to the edge effect and the following 4 factors

i. predominance of woody plant communities

-especially important when the rest of the forests have been destroyed

(a very wet forest tends to be the last to be developed)

-standing "snags" or dead trees

-shades stream, stabilizes bank, produces leaf litter

ii. presence of surface water and abundant moisture

-important source of water and food, travel (beavers and muskrats) and

protection

iii. diversity and interspersion of habitat features; lots of niches so lots of species

iv. corridors for dispersal and migration

-linear nature allows for protective pathways for animals on the move

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