INCORPORATION OF HEAVY METALS IN EXPERIMENTALLY GROWN FORAMINIFERA FROM SAPELO ISLAND, GEORGIA AND LITTLE DUCK KEY, FLORIDA, USA

Benthic foraminifera are valuable indicators in marine pollution monitoring. While most foraminiferal biomonitoring research utilizes abundance and distributional data, further value resides in better understanding the incorporation of heavy metal pollutants in foraminiferal calcite. By experimentally growing assemblages of foraminifera from propagules (small juveniles) gathered from Sapelo Island, Georgia and Little Duck Key Florida, this study examines foraminiferal incorporation of arsenic, cadmium, nickel, and zinc over a range of concentrations.

Surface sediment was collected and sieved to concentrate the propagules. The propagules were then used in experimentally grown assemblages with each assemblage exposed to a different heavy metal. Different concentrations of two essential elements (nickel and zinc) and two non-essential elements (arsenic and cadmium) were added. After one month, the resulting foraminifera were harvested and examples of the two most common calcareous species from each location (Ammonia tepida (Cushman) and Haynesina germanica (Ehrenberg) from Sapelo island and Quinqueloculina sabulosa Cushman and Triloculina oblonga (Montagu) from Little Duck Key) were selected. Calcite of the tests was analyzed using LA-ICP-MS to determine the amount of heavy metal incorporation.

Foraminifera incorporated all four of the metals in some capacity. Relatively minor variation in incorporation is present within individual foraminifera, with the exception of rotalid species exposed to nickel. Great intraspecific variation also occurs, especially in A. tepida and H. germanica exposed to arsenic and nickel. Clear differences exist between the rotalid and miliolid species in their response to essential and non-essential metals. Rotalid species A. tepida and H. germanica incorporated more of the non-essential metal cadmium as its concentration in the surrounding water increased, whereas miliolid species Q. sabulosa and T. oblonga incorporated more of the essential metals zinc and nickel as their water concentration increased. This study shows that while foraminiferal incorporation of heavy metals has great potential use as a biomonitoring tool, variation based on multiple potential factors must be considered carefully in future marine environmental research.