CHAPTER III: MISSISSIPPI’S ECOLOGICAL FRAMEWORK-ECOREGIONS OF MISSISSIPPI 69
Part 3: Northern Gulf of Mexico Ecoregion
The Northern Gulf of Mexico (NGM) ecoregion extends from Anclote Keys, Florida to the southern ex-
tent of the Laguna Madre de Temaulipas in Mexico. It is a rich and productive subtropical system that
supports some of the most extensive wetland and seagrass habitats in the world. Much of the nearshore
waters of the Gulf are divided into bay and estuarine systems behind barrier islands, which form a ring
of sites around the NGM. For the purposes of this CWCS habitats including barrier island systems with
annual-dominated beaches, maritime grasslands and scrub, maritime forests have been classified as part
of the NGM ecoregion. These grade through salt marshes to productive estuaries.
In Mississippi, the NGN borders the EGCP and is completely coincident with it. TNC has divided the
ecoregion into three broad subregions for planning purposes. Mississippi falls within the Central Gulf of
Mexico region which runs from Galveston Bay, Texas to Mobile Bay, Alabama. This region is charac-
terized by extremely high levels of riverine input. Freshwater and sediments from the Mississippi River
and to a lesser extent freshwater entering through Mobile Bay determine the characteristics of nearshore
waters in this region. Coastal waters are generally variable in salinity, and water clarity is low because of
the sediment load. Bottom sediments tend to be fine clays and muds. These conditions are ideal for the
growth of marshes and oyster reefs.
The drainage basin for the Gulf extends from the Appalachians to the Rockies. It contains nearly 60 per-
cent of the land area of the continental United States, including some the most fertile lands in the world.
This productive drainage makes the Gulf one of the primary producers of finfish and shellfish in the
United States. However, because much of this land is in agricultural use, fertilizers, herbicides and pesti-
cides threaten the productivity of the Gulf.
Northern Gulf of Mexico
Counties