Mobile Bay




Text modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment. Island Press, Washington, DC, USA. Additional text provided by Jennifer Hales.


United States

Major Habitat Type

Temperate floodplain rivers and wetlands

Drainages flowing into

The drainages of this ecoregion flow into the Gulf of Mexico.

Main rivers to other water bodies

The major rivers of the ecoregion include the Alabama and Mobile rivers, which drain into Mobile Bay at the Gulf of Mexico. Tributaries include the Tombigbee and Black Warrior rivers, which join to form the Mobile River. The Coosa, Tallapoosa, and Cahaba rivers are tributaries of the Alabama.



The Mobile Bay ecoregion encompasses the Mobile, Tombigbee-Black Warrior, and Alabama-Coosa-Talapossa basins, along with the drainages of numerous smaller streams and lakes. These connected systems form the largest drainage basin in the East Gulf Coastal Plain. This ecoregion is centered in central Alabama and includes eastern Mississippi, western Georgia, and a small area in southern Tennessee.


Above the Fall Line, the ecoregion’s rivers flow through the diverse topography of the Valley and Ridge Province, the Piedmont Upland, and the Appalachian Plateau. The rivers then descend into the East Gulf Coastal Plain, which is characterized by flat to rolling topography.

Freshwater habitats

Historically, rivers and streams in this ecoregion stretched over 1000 miles. Today, flow in the Mobile River is regulated by a series of upstream reservoirs on the Etowah, Coosa, and Tallapoosa rivers, and to a lesser extent by the locks and dams of the Tombigbee River (Livingston 1992; U.S. Fish and Wildlife Service Division of Endangered Species 1993; Stolzenburg 1997).

Terrestrial habitats

The northern part of the ecoregion is characterized by Appalachian Blue Ridge and Appalachian mixed mesophytic forests, considered some of the most biologically diverse temperate forests in the world. These grade into Southeastern mixed forests, which are demarcated from conifer forests in the south by the Fall Line of the Atlantic Piedmont. The conifer forests are fire-maintained systems dominated by long-leaf pine (Pinus palustris) (Ricketts et al. 1999).

Description of endemic fishes

In addition to supporting roughly 40 endemic species, it also shares a number with only one other ecoregion. Of particular interest are three species known only from a few isolated upland springs in this ecoregion - the coldwater darter (Etheostoma ditrema) and pygmy sculpin (Cottus paulus) of the Coosa drainage, and the endangered watercress darter (Etheostoma nuchale) of the Black Warrior drainage (Swift et al. 1986).

Justification for delineation

Ecoregion boundaries are taken from Abell et al. (2000) and are based on subregions defined by Maxwell et al. (1995).


  • American, Rivers (1997) \American Rivers’ most endangered and threatened rivers of 1997. Online.\ (Washington, DC, USA)
  • Livingston, R. J. (1992). "Medium-sized rivers of the Gulf Coastal Plain" Hackney, C. T.;Adams, S. M.;Martin, W. H. (Ed.) Biodiversity of the southeastern United States: aquatic communities ( pp. 351-385 ) New York, New York, USA.: John Wiley and Sons, Inc..
  • Ricketts, T. H.,E. Dinerstein,D.M Olson;C.J. Loucks (1999). "Terrestrial ecoregions of North America: A conservation assessment" Washington, D.C.: World Wildlife Fund.
  • Stolzenburg, W. (1997) \Sweet home Alabama\ The Nature Conservancy Magazine, September/October>
  • Swift, C. C., Gilbert, C. R., Bortone, S. A., et al. (1986). "Zoogeography of the freshwater fishes of the southeastern United States: Savannah River to Lake Pontchartrain" C. H. Hocutt and E. O. Wiley (Ed.) The zoogeography of North American freshwater fishes ( pp. 213-265 ) New York, New York, USA: Wiley.
  • Abell, R.,Olson, D.,Dinerstein, E.,Hurley, P. T.,Diggs, J. T.,Eichbaum, W.,Walters, S.,Wettengel, W.,Allnutt, T.,Loucks, C. J.;Hedao, P. (2000). "Freshwater ecoregions of North America" Washington, D.C.: Island Press.
  • Maxwell, J. R., Edwards, C. J., Jensen, M. E., et al. (1995) \A hierarchical framework of aquatic ecological units in North America (Nearctic Zone)\ St. Paul, MN. North Central Forest Experiment Station, USDA Forest Service.
  • Köppen, W. (1936). "Das geographische System der Klimate" Köppen W. and R. Geiger (Ed.) Handbuch der. Klimatologie ( (Vol. 1, pp. 1–44 ) Berlin, Germany: Gebrüder Borntröger.