Diamondback terrapins (Malaclemys terrapin) are the subject of this continuing project which will test the hypothesis that the diamondback can prove to be a powerful sentinel species to help track the accumulation and degradation of contaminants in estuarine and coastal environments.
Objectives of this study are to (1) Complete the long-term mercury feeding study and determine if bioaccumulation is occurring and finalize assessment of the validity of non-lethal blood and keratin sampling techniques, (2) Test the relationship of health endpoints to long-term mercury exposure, including reproductive, behavioral, and endocrine and (3) Determine if terrapins can be useful as a sentinel species for estuarine settings by linking terrapin sampling locations to existing projects investigating local mercury contamination, water quality parameters, and land-use criteria. To-date there has been several interesting findings. The larger females do have significantly higher Hg levels than the males which most likely relates to their prey items since females eat larger periwinkles (Littorina) than males do and larger periwinkles also have significantly higher Hg (121 ppb vs. 19 ppb). There is also a clear and significant seasonal drop in blood Hg in terrapins (both sexes) during August when they are maximally active metabolically. Our sampling in Georgia at the Purvis Creek super fund site (location of a former chlorine manufacturing plant) showed significantly elevated blood (746 ppb) and scute (3810 ppb) Hg at 10X or more higher levels than our sites in South Carolina. The female terrapins at Purvis Creek were also significantly smaller and showed indications of immunological deficiencies so they may have been directly impacted by the mercury.
The results will, in addition to being useful to terrapin conservation, also establish basic toxicity thresholds that may be relevant for other threatened reptilian taxa, such as sea turtles, that utilize estuaries. In addition, the biomonitoring tool to be developed should prove useful for resource management agencies, public health officials, and environmental impact assessment and remediation.