14C-labeled tributyltin-chloride (TBT-Cl) was delivered to the water column of seagrass microcosms held in the laboratory under flow-through conditions. Benthic macroinvertebrate abundances across a three treatment, logarithmic dose gradient were compared to untreated control microcosms. Within 3 to 6 weeks, statistically significant mortality appeared in the high treatment. Sensitive species included surface deposit feeders of several phyla, as well as a suspension feeding mollusc. Results suggest that effects can arise because TBT is rapidly accumulated in surface sediments, as well as in Thalassia tissues. Concentration of tracer in plant tissues, animals, and sediments suggests that measurement of TBT (and total butyltin) in these components of seagrass beds would provide a better indicator of exposure regimes than occasional measurements in the water. A propensity for accumulation, along with a biological vulnerability, suggests a sentinel role for seagrass ecosystems in some shallow coastal areas. Experimental findings demonstrate concern for some key invertebrates within beds proximal to TBT sources, and ecological risks could radiate through coastal food webs dependent on these productive vegetated shallows.
Bibliographical noteFunding Information:
We thank Gayle Plaia for species identifications; Karen McClathery for assistance during breakdown of the experiment, for associated field measurements, and for doing the gypsum dissolution measurements; and Dr Charles D'Asaro, University of West Florida, for additional assistance through Cooperative Agreement Number CR811649 with the US EPA Gulf Breeze Laboratory. We are indebted to Al Uhler, Battelle Ocean Science (Duxbury MA), for organotin analysis of several animal tissue and sediment samples. Additionally, we thank Tom Duke for initiating this project and for constructive comments on the manuscript. Dave Flemer served as project officer and assisted at many times; his efforts and comments were most helpful. Our friend and colleague Mark Harwell was instrumental in the initial design of the project. This publication is ERC-204 of the Ecosystems Research Center (ERC) Cornell University. Partial funding was provided under the US EPA Ecological Risk Assessment Program from the Gulf Breeze EPA laboratory through US Environmental Protection Agency Cooperative Agreement Numbers CR812685, CR812685-02 and CR812685-03. Additional funding was provided by Cornell University and the University of West Florida. The work and conclusions published herein represent the views of the authors, and do not necessarily represent the opinions, policies, or recommendations of the Environmental Protection Agency.