THE EFFECT OF INCREASED SALINITY ON FORAMINIFERAL ASSEMBLAGES IN GEORGIA SALT MARSHES

Foraminifera are sensitive indicators of environmental and climatic change in marine and coastal environments. Previous studies have shown that the taxonomic composition of foraminiferal assemblages within salt marshes reflects the salinity conditions of the marsh, which is in turn influenced by tidal patterns, runoff, and prevailing climatic conditions. Foraminiferal assemblages should therefore respond to changes in salinity conditions such as those that occur due to increased evaporation and decreased precipitation. Drought frequency and intensity is predicted to increase as a result of modern climate change, with potentially negative effects to salt marsh communities.

During the summer of 2011, salt marshes along the Georgia coast experienced severe drought, which resulted in elevated salinities in marshes that are typically hyposaline. This study examines the extent to which this observed change in environmental conditions affects diversity and relative abundances in salt marsh foraminiferal assemblages. Results will provide a better understanding of the response of foraminifera to increased salinity conditions.

To determine the impact of the summer 2011 drought on Georgia salt marsh foraminifera, surface and subsurface sediment samples were collected at three selected sites along a salinity gradient within the Altamaha River and Sound system near Darien, Georgia. All samples were fixed and stained immediately after collection using a mixture of 4% buffered formalin with 0.1% rose Bengal. Once in the lab, samples were washed and sieved (63 microns) and foraminifera were picked and identified to the species level. A live–dead analysis was conducted, in which diversity and abundance patterns of living assemblages were compared with the corresponding time-averaged death assemblages. Preliminary results indicate that while both assemblages have an overall low biodiversity, the death assemblages have greater abundances and higher diversity than the corresponding living assemblages.