Abstract

Benthic foraminifera are valuable environmental indicators of heavy metal contaminants in marine environments. To broaden their effectiveness as bioindicators, this study compares individually the effects of selected heavy metal contaminants, including both metabolically essential and non-essential elements, on temperate rotalids and subtropical miliolids, as well as associated monothalamid foraminifera. To accomplish these aims, assemblages of foraminifera were grown experimentally from propagules (small juveniles) collected from two coastal sites: Sapelo Island, Georgia, and Little Duck Key, Florida, that provide an effective comparison between environments and types of 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. Two metabolically essential trace elements, nickel, and zinc, and two non-essential elements, arsenic and cadmium were used to represent both types of heavy metal. Experimental conditions were held constant while varying only the metal concentrations.

In treatments from both origins, increasing concentrations of cadmium, nickel, and zinc led to decreases in abundance and diversity for the foraminifera. In addition, zinc, and to a lesser extent cadmium and nickel above certain concentrations, resulted in an increase of deformed tests among the foraminifera. Deformities occurred amongst the most common calcareous species from Sapelo island: Ammonia tepida and Haynesina germanica. Fewer deformities were observed in common calcareous species from Little Duck Key, the miliolids Quinqueloculina sabulosa and Quinqueloculina bosciana featured few deformities. Notably, monothalamid species such as Psammophaga sapela remained present at high metal concentrations. These results support previous research and reinforce the usefulness of rotalids such as A. tepida and H. germanica as bioindicators of heavy metal contamination as well as suggesting a possible use of monothalamids such as P. sapela in this manner.

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