This is a sample of the information contained in the Estuarine
Ecology Appendix of the Estuary-Net Project.
ESTUARINE HABITATS AND COMMUNITIES
THE MARSH
Salt marshes are a common type of wetland of extreme importance
to the balance of certain estuarine ecosystems. Marshes are dominated by
important grasses that provide food and shelter to marine organisms that
are permanent and transient residents of the estuary. Marshes are divided
into two basic zones: high marsh and low marsh, which are defined by differences
in flooding and soil salinity. Marshes usually have different bands of
vegetation creating high and low zones within the marsh.
Despite its varied and lush vegetation, the marsh is home to
relatively few terrestrial animals. Deer, migratory birds, grasshoppers
and other animals consume marsh grasses. Small animals, such as shrews
and mice, provide prey for larger mammals and birds of prey that also live
in or around the marsh.
Marsh grasses are thought to be low in nutritive value and
to contain toxic compounds; so even with all of these consumers little
of the vegetation is eaten. Rather, most of the plants die and are deposited
on the ground to become peat. Some pieces of the plants are then washed
into the water to become detritus, decaying particles coated with bacteria,
which serve as a nutrient base for the estuarine food web. Detritus is
consumed by filter-feeders such as clams, detritivores such as mummichogs,
and deposit feeders such as polychaete worms. In general, estuaries are
known as hosts for abundant aquatic and avian, rather then terrestrial,
animals.
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