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Our
Salt Marshes
December 2007 Palmetto Perspective
by Dianne Faucette, Master
Naturalist
You
may wonder…why isn’t our ocean water as clear and pretty as the
water in the Caribbean?
I’ll
begin by describing what is in our local waters. Beaufort
County possesses half of the salt marsh in South Carolina, and half
of Beaufort County is salt marsh. The obvious characteristic of our
salt marshes is the smooth cordgrass, Spartina
alterniflora, which unlike any other plant, thrives in the high
salinity water from the ocean. The often-heard-but-rarely-seen
Clapper rails build nests in the marsh vegetation. As the perennial Spartina
dies and breaks off (becoming “wrack”), it clumps together and
floats on the rising and falling tide, sometimes providing nesting
habitat for animals such as mink, which I have observed in Broad
Creek. The wrack decomposes and becomes phytoplankton—microscopic
plant organisms which are carried by water currents.
Our
abundant phytoplankton is the basis for the coastal aquatic food web
and is responsible for the green tint of the summer ocean water.
Fungi and algae grow on the decomposed Spartina
and provide food for oysters as it floats through the water, and
food for fiddler crabs and mud snails after it settles on top of the
marsh mud. (In turn, fiddler crabs are eaten by white ibises and
shorebirds at low tide.) Phytoplankton that becomes attached to Spartina
stalks is eaten by marsh periwinkles as they climb and descend the
grass to stay above the moving tide levels.
Another
kind of plankton is zooplankton—microscopic animals and crab and
shrimp larvae which feed on phytoplankton. Shrimp reproduce in
nearshore ocean waters, but their larvae are swept into our creeks
by currents to mature. Marshes provide protection from predators and
are sometimes referred to as “nurseries” for shrimp as well as
oysters and other creatures.
Young
oysters float around like plankton for their first two to three
weeks before cementing themselves to another hard surface (usually
other oysters) for protection. During their three-year lifetime
(before becoming market size), oysters eat algae, remove silt and
improve water quality by filtering up to 50 gallons a day. Oysters
are a “keystone” species which means they make beneficial
changes to their environment. In addition to filtering the water,
oyster beds create habitat for many fish and protect the marsh and
banks by reducing wave energy.
Our
unclear water provides a healthy habitat. Without the components
that keep it from being clear, we would have no delicious shrimp,
crabs, or oysters! |
