Cover

CHAPTER IV: WILDLIFE HABITATS FOR MISSISSIPPI’S SGCN,

THREATS AND CONSERVATION ACTIONS^255

14.1 Estuarine Bays, Lakes and Tidal

Streams

„ Value to SGCN - 100

„ Rank - 3rd of 17 Marine, Estuarine and

Estuarine Fringe Systems

DESCRIPTION
The term embayment refers to large, protected, low
energy, subtidal areas that are enclosed on three sides
by land. Mississippi has two such embayments, St.
Louis Bay and Biloxi Bay. The bays range in depth
from one to ten feet, except in minor channel segments
where the depth reaches 30 feet. The textures of bottom substrates range from muddy sand to sandy
mud. Bays are partially-mixed to well-mixed systems, depending on the season and experience tidal
surges of one to one and one-half feet on average, but occasionally reach four feet. Salinity levels are in
a constant state of flux depending on the ebb and flow of the tides and weather systems impacting the
region and season. Additional parameters defining these waters include turbidity, pH, dissolved oxygen,
nutrients and chlorophyll levels. The muddy bottoms support a diverse group of benthic life forms,
mainly polychaetes, mollusks, insects and crustaceans, many of which prefer the bays over other
estuarine areas. Numerous species inhabit the coastal bay waters, and the most economically important
are anchovies, catfish, sea trout, spot, croaker, shrimp and blue crabs. Bays and bayous are important
foraging areas for many birds such as loons, grebes, pelicans, herons, gulls and terns.

Besides coastal bays, coastal ponds and lakes contribute additional open water estuarine habitat. There
are over 100 coastal estuarine ponds of many different sizes totaling almost 4,000 acres. Examples
include Bangs Lake and Graveline Bayou in Jackson County. The lakes are usually very shallow, from
one to ten feet deep and contain a similar complement of aquatic species to those found in bays. The
small, circular or oval ponds and lagoons of the barrier islands also number in the hundreds. Due to
their shallow nature and differences in connectivity, they exhibit a wider range of temperatures and
salinity levels than mainland ponds. The ponds harbor a diverse group of fishes and birds. When
exposed to hurricane winds, these ponds are radically changed through overwash, erosion and species
exchanges.

Mississippi's tidal streams can be classified into three general types: tidal marsh creeks, coastal tidal
creeks and riverine estuary bayous. Tidal marsh creeks primarily drain estuarine marshes. Coastal tidal
creeks serve as minor conduits for freshwater discharge from surrounding uplands. Riverine estuary
bayous serve as interdistributary channels within riverine estuaries. Substrates are usually muddy sand
or sandy. Salinity, pH and turbidity change along a gradient that extends from the upper reaches of tidal