TEST DEFORMATION, ABUNDANCE, AND DIVERSITY RESPONSES OF BENTHIC FORAMINIFERA TO HEAVY METAL POLLUTANTS: AN EXPERIMENTAL APPROACH

To better understand the application of benthic Foraminifera in field-based pollution studies, a pilot study was conducted to examine the response of some common species of shallow-water, temperate Foraminifera grown in the lab with exposure to selected heavy metal contaminants (Cd, Hg, Pb, Zn). Sediments, collected from a natural, pristine mudflat on Sapelo Island, GA, were sieved, and the <63-µm fraction was retained for use in subsequent experiments. This fine sediment fraction, which contains a large number of tiny juvenile foraminifers from the natural environment, was subdivided into a series of 20-ml aliquots, each placed in an experimental container with 40 ml of Instant Ocean (~30 psu) and a specified concentration of a single heavy-metal contaminant. Concentrations were based on the EPA National Recommended Water Quality Criteria for Saltwater (Cd 40 µg/L, Hg 1.8 µg/L, Pb 210 µg/L , Zn 90 µg/L) and increased by an order of magnitude for 4 concentration levels of each heavy metal. The experimental containers were kept at a constant temperature (18° C) and illuminated on a 12-hr cycle. Replicates and controls were also run. All containers were harvested after 4 weeks, fixed and stained (formalin / rose Bengal), and sieved again at 63 µm. The material >63 µm contained assemblages of foraminifers that had grown during the course of the experiment, and these were examined for abundance, diversity, and the presence of deformed tests. Experimental assemblages were dominated by Ammonia tepida, Haynesina germanica, Psammophaga simplora, and Ovammina opaca. Hg and Pb had no major affect on test deformation and abundances at all experimental concentration levels. Zn levels of 90000 µg/L produced significant test deformation, particularly in Haynesina germinica. Cd levels of 40000 µg/L did not produce abundant test deformations but resulted in decreased abundances. Replicate samples produced similar results, and collectively results indicate that Foraminifera respond to the presence of individual heavy metal contaminants, but that overall assemblages respond to each contaminant differently.