Coastal Wetland Ecosystems

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Coastal Wetland Ecosystems
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Tidal Salt Marshes
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Tidal wetlands are crucial "ecotones" that is,
they form highly productive environmental buffers
between terrestrial, freshwater and marine
systems
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Salt marshes are transitional areas between land
and water, occurring along the intertidal shore
of estuaries and sounds where salinity (salt
content) ranges from near ocean strength to near
fresh in upriver marshes.
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Because salt marshes are influenced by the twice
daily rise and fall of tides, they are subject to
rapid changes in salinity, temperature and water
depth.
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Salinity, frequency and extent of flooding of the
marsh determine the types of plants and animals
found there
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The low marsh zone frequently floods twice
dailyThe high marsh floods only during storms
and unusually high tides
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Low to high marsh transition, West Galveston Bay
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Tidal creeks, open water, and tidal flats are
also important components of the marsh ecosystem
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Animals and plants that live in these zones
must be able to tolerate the drier conditions of
the upper marsh or the wet conditions that
regularly occur in the lower marsh.
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Smooth cordgrass (Spartina alterniflora),
dominates the regularly flooded low marsh.
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Spartina seedlings
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Spartina alterniflora, flowering
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Courtesy T. Michot, USGS, National Wetlands
Research Center
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Live Spartina is not a source of food but dead
marsh plants are a source of nourishment for many
species. Decaying Spartina breaks into small
pieces called detritus that fuels the marsh and
its animals.
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Fiddler crabs, marsh snails and marsh mussels are
typical invertebrate species which live in salt
marshes. Fiddler crabs and marsh snails shred
dead plant material during feeding, aiding the
decomposition process.
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Salt Marsh Functions

• major producer of detritus and provide nursery
  grounds for numerous commercially and
  recreationally important species
• filters to remove sediments and toxins from the
  water
• Marsh plants break down many pollutants into less
  harmful forms

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Over half of our original salt marshes in the
United States have been destroyed, many of them
between 1950 and the mid-1970s.
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Most of that destruction was due to filling of
marshes to create more land area for homes,
industry and agriculture
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Tidal Freshwater Marshes
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Tidal freshwater marshes are found upstream of
estuaries where the tides still influence water
levels, but where the water is predominantly
fresh.
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Tidal freshwater marshes receive substantial
water and nutrients from upstream water
resources, as well as inputs from runoff and
precipitation
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Tidal freshwater marshes provide habitat, food,
shelter, and nurseries for many fish and
shellfish. In addition, approximately half of the
organic matter produced in these marshes is
transported downstream to the estuary or the sea
as detritus, forming the base of the food web.
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Some fish species, such as minnows, carp,
sunfish, bass, and catfish, spend their entire
life cycle in tidal freshwater marshes
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Other fish and shellfish rely on the freshwater
marshes for parts of their life cycle and spend
the remainder of their lives in the marine
environment
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Coastal freshwater marshes may support the
largest and most diverse bird populations of all
wetland habitats.
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Estimated to cover 164,000 hectares along the
middle Atlantic coast, about half of these
marshes are located in New Jersey
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Gulf of Mexico freshwater wetlands are
concentrated in Louisiana, where they cove about
468,000 hectares.
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Baldcypress, (Red-eye Swamp, Atchafalaya basin)
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Dominant Plant Species

• Arrow arum, with arrow-shaped leaves up to three
  feet wide and white flowers
• Pickerel weed, with heart-shaped leaves and blue
  flowers
• Yellow pond lily, or spatterdock, with
  heart-shaped leaves and a single yellow flower
• Big-leafed arrowhead, with arrow-shaped leaves
  and white three-petaled flowers with yellow
  centers on an elongate stalk and
• Blue flag, a native iris with a poisonous
  rootstock, long flat leaves and blue-violet
  flowers

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Arrow Arum
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Tidal salt marshes are efficient nitrogen
transformers because of the daily hydrologic
cycle, which removes a significant portion of
total inputs from the aquatic system in the form
of gaseous nitrogen
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Mangrove Wetlands
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The majority of the subtropical and tropical
coastline is dominated by mangroves, estimated to
cover an area of 22 million hectares.
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These complex ecosystems are found between the
latitudes of 32 degrees north and 38 degrees
south, along the tropical coasts of Africa,
Australia, Asia, and the Americas
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Over the past several decades, the global area in
mangroves has increasingly diminished as a result
of a variety of human activities, such as
overharvesting, freshwater diversion and
conversion to other uses.
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Mangrove forests are comprised of taxonomically
diverse, salt-tolerant tree and other plant
species which thrive in inter-tidal zones of
sheltered tropical shores, "overwash" islands,
and estuaries
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Mangrove trees have specially adapted aerial and
salt-filtering roots and salt-excreting leaves
that enable them to occupy the saline wetlands.
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The forest detritus, consisting mainly of fallen
leaves and branches from the mangroves, provides
nutrients for the marine environment and supports
immense varieties of sea life in intricate food
webs.
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Mangroves help protect coastlines from erosion,
storm damage, and wave action.
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A primary factor of the natural environment that
affects mangroves over the long term is sea level
and its fluctuations.
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Globally, as much as 50 percent of mangrove
destruction in recent years has been due to clear
cutting for shrimp farms.
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