2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 4
Presentation Time: 8:45 AM


ISPHORDING, Wayne C., Earth Sciences, Univ of South Alabama, LSCB 136, Mobile, AL 36688 and ENRIGHT, Richard L.C., Jr, Bridgewater State College, Dept Earth Science & Geography, Bridgewater, MA 02325, wisphord@jaguar1.usouthal.edu

Perdido Bay lies on the Alabama-Florida border and has a surface area of slightly greater than 130 sq km. Similar to other bays in the northern Gulf of Mexico, its origin can be traced to flooding of an ancient stream valley that began in the late Pleistocene. Maximum water depths are on the order of 4 m and the bay is separated from the Gulf of Mexico by a narrow pass to the Gulf and a prominent barrier island.

Written accounts, supported by analysis of core samples, confirm that the bay was historically a freshwater system and contained a thriving submerged aquatic vegetation. The opening of a pass into the Gulf of Mexico in the early 20th century created the present saltwater (brackish) system. Prior to the 1940's, the bay was in a nearly pristine state and was characterized by clear water, a white sand bottom, and an abundant biota that included many species of fish and shellfish. This diversity and abundance, however, has been severely impacted by the activities of man. Accelerated municipal and urban development has created stress in the bay and a significant impact has also been traced to paper manufacturing that began over 60 years ago. Riparian property owners have expressed concern about large quantities of a fine grained, black material (described by residents as “black mayonnaise”) that is especially common in the upper bay. This material has frequently been driven onto adjacent residential properties during storms and abnormally high tides and has been observed by divers as occurring as a several inch thick, “flocculant clay-colloidal layer” that is suspended just above the sediment-water interface. This substance is also characterized by anomalous levels of heavy metals, adsorbable organic halides (AOX compounds), organic carbon, nitrogen, and dioxins. Detailed sampling has traced the material to paper mill effluent discharged into a tributary creek that empties into the bay. Significant changes have taken place as a consequence of this effluent, including the total disappearance of oysters and other shellfish in the upper bay and degredation of water and sediment quality elsewhere in the bay. While paper mill effluent may not be the cause of all of the bay's problems, State and Federal agencies, as well as independent researchers, have shown that most of the bay's problems can be traced directly to this single, anthropogenic source.