Tributyltin and invertebrates of a seagrass ecosystem: Exposure and response of different species

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.