EFFECT OF SELECTED HEAVY METAL ELEMENTS ON SHALLOW-WATER BENTHIC FORAMINIFERAL ASSEMBLAGES FROM SAPELO ISLAND, GEORGIA AND LITTLE DUCK KEY, FLORIDA: AN INVESTIGATION USING THE PROPAGULE METHOD

Benthic foraminifera are valuable environmental indicators of heavy metal pollutants in marine environments. In this study, we examine the effect of a suite of heavy metal pollutants, tested individually, on the abundance, diversity, potential shell deformity, and differential species response of foraminiferal assemblages grown experimentally from propagules, small juvenile foraminifera collected from sediment samples at two coastal sites: Sapelo Island, Georgia and Little Duck Key, Florida.

Sapelo Island, a barrier island in southeast Georgia, represents a temperate climate with abundant mudflats, salt marshes, and rotalid foraminifera. Little Duck Key, a small key in the middle Florida Keys, features a sub-tropical climate with a large back-reef area and hosts more miliolid foraminifera. Surface sediment was collected from both locations and sieved immediately after collection. Using the propagule method, assemblages of foraminifera were grown in the laboratory from propagules in the sediment samples, with each assemblage exposed to a different heavy metal. Two essential elements, copper and zinc, and two non-essential elements, arsenic and cadmium were used to represent both types of heavy metal.

In both the Sapelo Island and Little Duck Key assemblages, concentrations of cadmium, copper, and zinc led to decreases in abundance and diversity for the foraminifera. The evidence suggests a strong negative relationship between a growing concentration of these metals and abundance and diversity of the population. In addition, zinc and to a lesser extent cadmium and copper at certain levels of concentration resulted in an increase of deformed tests among the foraminifera. Deformities were especially prevalent amongst the most common genera in each location: Ammonia and Haynesina from Sapelo Island, and Quinqueloculina and Triloculina from Little Duck Key. All of these results support previous research and reinforce the usefulness of foraminifera as bioindicators.