Mobile Bay is the terminus of the fourth largest river system in terms of discharge in the United States. Currently, an annual average of 4.3 million metric tons of suspended sediment and an unknown quantity of bed load are being transported into the estuary. The dominant terrigenous clastics are quartz, kaolinite, and montmorillonite.

Circulation patterns within t he estuary are controlled primarily by river discharge, tides, and geometry of the bay. Meteorological tides cause important short-term variations. Depending upon the season and (or) year, the estuary may be classified as highly stratified, moderately stratified, or, with the exclusion of the...