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Abstract
Benthic foraminifera have a long history as environmental indicators of heavy-metal contaminants in marine environments. This study compares the effects of selected heavy metal contaminants (arsenic, cadmium, nickel, and zinc) on benthic foraminifera, grown experimentally from propagules (small juveniles) collected from two coastal sites: Sapelo Island, Georgia, and Little Duck Key, Florida.
Surface sediment was collected from both locations and sieved immediately after collection. The propagules were then used to experimentally grow assemblages with each assemblage exposed to a different heavy metal. The goal here was to compare the effects of these heavy metals on the abundance, diversity, and possible test deformities in benthic foraminifera while also comparing possible different responses of rotalid, miliolid, as well as monothalamid foraminifera. Samples of the two most common 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 then selected for trace element analysis using LA-ICP-MS to quantify possible heavy-metal incorporation among the foraminifera. Finally, additional experimental foraminiferal assemblages were grown under different temperature and salinity regimes, including intermediate (22°C, 32 psu), elevated temperature (30°C, 32 psu), reduced temperature (18°C, 32 psu), elevated salinity (22°C, 40 psu), and reduced salinity (22°C, 12 psu) in an attempt to identify possible effects of salinity and temperature change on heavy-metal impact on foraminifera.
Increasing concentrations of the trace elements led to decreases in abundance and diversity for the foraminifera. Elevated concentrations above a certain threshold, especially with zinc, resulted in an increase of deformed tests among the foraminifera. However, test deformities did not consistently occur in different salinities and temperatures. Differences exist between the rotalid and miliolid species in their incorporation of the heavy metals. Rotalid species incorporated more cadmium as its concentration in the surrounding water increased, whereas miliolid species incorporated more of the metals zinc and nickel. These results underscore the importance of foraminifera as bioindicators, but also show that several factors, such as interspecific variation and environmental variability must be considered in using foraminifera in pollution studies.
Surface sediment was collected from both locations and sieved immediately after collection. The propagules were then used to experimentally grow assemblages with each assemblage exposed to a different heavy metal. The goal here was to compare the effects of these heavy metals on the abundance, diversity, and possible test deformities in benthic foraminifera while also comparing possible different responses of rotalid, miliolid, as well as monothalamid foraminifera. Samples of the two most common 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 then selected for trace element analysis using LA-ICP-MS to quantify possible heavy-metal incorporation among the foraminifera. Finally, additional experimental foraminiferal assemblages were grown under different temperature and salinity regimes, including intermediate (22°C, 32 psu), elevated temperature (30°C, 32 psu), reduced temperature (18°C, 32 psu), elevated salinity (22°C, 40 psu), and reduced salinity (22°C, 12 psu) in an attempt to identify possible effects of salinity and temperature change on heavy-metal impact on foraminifera.
Increasing concentrations of the trace elements led to decreases in abundance and diversity for the foraminifera. Elevated concentrations above a certain threshold, especially with zinc, resulted in an increase of deformed tests among the foraminifera. However, test deformities did not consistently occur in different salinities and temperatures. Differences exist between the rotalid and miliolid species in their incorporation of the heavy metals. Rotalid species incorporated more cadmium as its concentration in the surrounding water increased, whereas miliolid species incorporated more of the metals zinc and nickel. These results underscore the importance of foraminifera as bioindicators, but also show that several factors, such as interspecific variation and environmental variability must be considered in using foraminifera in pollution studies.