AN ANALYSIS OF BENTHIC FORAMINIFERA ACROSS THE GEORGIA CONTINENTAL SHELF

The purpose of this study was to: 1) determine the density of living (Rose Bengal stained) and fossil foraminifera in surface sediments at 5 stations across the inner- and mid- shelf regions off Savannah, Georgia; and 2) examine the potential influences of water depth, salinity, temperature, and grain size distributions on the living community. Samples were collected on 3 different cruises aboard the R/V Savannah using a modified box corer and the upper 3 cm of each core was analyzed.

The range in bottom water salinity was minimal during sample collection at the 5 stations (34.3 – 36.4 PSU) and there was no relationship found between bottom water salinity and density of living or fossil foraminifera. The density of fossil foraminifera increased from 149/10 ml sediment at 18.3 m water depth to 488/10 ml sediment at 34.6 m water depth, but the density at the shallowest site (15.3 m) was also high (415/10 ml) and did not follow the trend of increasing fossil foraminifera densities with increasing water depth. Densities of living foraminifera did not co-vary with water depth. There was, however, a consistent direct relationship between bottom water temperature and the density of living foraminifera, suggesting that living foraminifera are more abundant in the warmer seasons. Samples collected in July and October when bottom water temperatures were 25.0 and 24.1°C, respectively, had densities of live foraminifera 4 to 7 times greater than samples collected in March when bottom water temperatures were 14.3 to 16.5°C.

Grain size analyses suggest that particle transport and depositional processes may also play a role in controlling the distribution of benthic foraminifera on the shelf. Stations 1 and 5 had modal grain sizes in the coarse to very coarse sand range (34.6 m) and had the highest densities of fossil and total benthic foraminifera. Stations 2, 3, and 4 had modal grain sizes in the fine sand fraction and had lower densities of fossil and total benthic foraminifera. Cibicides appears to be the most abundant genus and was present at all 5 sample stations.