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Presenters Notified: November 2012

Program Schedule Posted:November 2012

Abstracts Available: January 2013

Meeting:
17-22 February 2013

Osterman, L. E., U.S. Geological Survey, USA, osterman@usgs.gov
Smith, C. G., U.S. Geological Survey, USA, cgsmith@usgs.gov

A CENTURY OF ENVIRONMENTAL DEGRADATION IN MOBILE BAY, ALABAMA, USA, RECORDED BY FORAMINIFERS

The marine microfauna of Mobile Bay has been profoundly influenced by the development and expansion of the primary shipping channel. Foraminifers and sediments from seven box cores with excess lead-210 chronology document that during the last century channel dredging and spoil disposal have altered circulation, estuarine mixing, and sedimentation patterns in Mobile Bay. Overall changes in estuarine mixing allowed for a greater low-pH freshwater influence in the bay. As a result, the sediment cores record a 100-year trend of increasing calcareous foraminiferal dissolution. In addition, reduced tidal flushing and increased terrestrial organic matter, documented by carbon-to-nitrogen ratios, have stimulated an increase in agglutinated foraminiferal densities in the more isolated western bay. However, in deeper regions of the bay, hypoxic water formation has negatively impacted the marine microfauna. The biologic degradation observed in the foraminifers agrees with the observed loss of oysters and submerged aquatic vegetation from Mobile Bay during the last century.

Oral presentation

Session #:SS25
Date: 2/22/2013
Time: 13:45