New testing methods utilized by South Carolina Sea Grant ecotoxologist Thomas Chandler show that thriving estuarine habitats can help absorb and reduce some impacts of toxic chemicals on aquatic creatures. Speaking of previous methods, Chandler says, "You can get an overestimate of a substance's toxicity to the multitude of species in an estuary based only on a single-species test in the lab." Chandler and his colleague, Bruce Coull, took an intact community of five species of copepods (tiny shrimp-like creatures) from an estuary and kept it in a healthy state. He then exposed the copepods to increasing doses of chlorpyrifos, a commonly used insecticide, looking for sublethal affects. "Chlorpyrifos can be very toxic to invertebrates such as shrimp and copepods, shutting down nerve function." Yet, they could find no effect on the copepods in an intact community at a dose that will kill 50 percent of the organisms in a lab single-species test. At higher levels, some problems began to develop, but in a natural environment where huge amounts of water heavily dilute chemicals, such levels are unlikely. "Perhaps the pesticide binds to carbon-rich particles in the sediment of the intact community, or bacteria break down the chemical making it less available," Chandler speculates. He hopes that his findings will lead to improved ecosystems-based approaches to pollution regulations and legislation.
CONTACT: Thomas Chandler, South
Carolina Sea Grant (O) 803-777-9481,