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Salt marshes make up
a
narrow fringe on the back of barrier islands and on the
mainland. This a picture of a fringe marsh.
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Fiddler crabs live
among the stems of marsh grasses. |
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A salt marsh on Bald Head Island.
See how some parts of
the marsh have deeper water that others.
There are also many "islands" or
hummocks in the marsh.
These areas are higher than the rest of the
marsh and rarely flood. The hummocks are home to trees and
shrubs that can not survive daily flooding. |
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Tidal creeks in a salt marsh, as seen from
the top of the Old Baldy lighthouse |
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What is a salt marsh?
From a distance, salt marshes look like vast, wet fields.
The whole marsh looks the same. All you see is water, mud,
and one or two kinds
of grasses. How can a place that seems so simple be so
important?
Actually, salt
marshes are complex ecosystems.
Many different plants,
animals, and microbes
live there. They exist in a fragile balance with their
environment and with each other. Salt marshes are also
very important to the estuaries and other coastal waters that
surround them.
The
tides
are the most important part of the salt marsh.
They bring sea water into and out of the marsh twice a day.
The organisms
that live in salt marshes must be able to live in salty water
and salty soils. At high tide, the marsh can be completely
covered with water. At low tide, it can be completely dry
and exposed to the sun. Salt marsh organisms have to
be able to live in both wet and dry conditions.
Where are salt marshes found?
Salt marshes are found on
shorelines that are
sheltered from ocean waves.
Some salt marshes are narrow,
fringing marshes.
They are found on steep coasts, between the water and dry land. Other salt marshes can be several miles wide.
These marshes are often found near the mouths of rivers, in
bays, and in protected
lagoons.
In warmer climates, mangrove trees take the place of marshes.
These trees are adapted to both a warmer climate and salt water.
In the Americas, they are found along coastlines in Florida,
Mexico, and in Central and South America.
Like most
barrier islands,
there are salt marshes along the back side of Bald Head Island.
These marshes are very large because of the shallow water in the Cape
Fear river estuary.
Tidal Flushing
Most salt marshes are flooded twice a day by the high tide.
Water flows into and out of the marsh through a maze of winding
tidal creeks. This tidal
flooding is important to the marsh ecosystem.
Daily flooding by salt water affects which plants grow in the
marsh. Very few plants can survive in such a salty
environment. As the tide water moves into and out of the
marsh, it carries detritus
from the marsh out into the estuary. This salt marsh
detritus is an important
food source for marine
organisms.
Click on the aerial photograph at left to
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