STRATEGIES FOR USING SHALLOW-WATER BENTHIC FORAMINIFERS AS BIOINDICATORS OF POTENTIALLY TOXIC ELEMENTS: A REVIEW

This review examines environmental factors affecting potentially toxic elements (PTEs) in coastal waters with the goal of proposing ways to enhance the use of benthic foraminifers as bioindicators of such pollution. Pollution of coastal systems by PTEs, often referred to as heavy metals, is a major concern for scientists, resource managers, and regulatory agencies. Bioavailability, uptake rates, speciation, clay mineralogy, pH, complexation, and other factors control the behavior of PTEs in marine systems, especially in estuaries. While breakthrough work has examined incorporation and assimilation of metals into marine macroinvertebrates, similar research on marine protists is still in the developmental stage. Many studies assume or conclude that foraminiferal assemblages and the frequency of deformed tests are first-line indicators of pollution, but others present confounding results. Understanding the complex geochemistries of PTEs, coastal waters, and sediments is critical to the design and interpretation of meaningful studies. Applications of foraminifers as bioindicators require strong scientific models based on both field and laboratory experiments and which specifically examine the influence of PTEs and other pollutants at community, assemblage, population, individual, and gene-expression levels. Genomic studies of key foraminiferal taxa with strong potential as bioindicators are critically needed as a basis for studies of gene expression indicating exposure to specific stressors. Though major challenges exist to fully realizing the potential for application of foraminifers as environmental indicators, their global importance in the past and present argues strongly for further development of these promising tools.