Porewater toxicity testing: A novel approach for assessing contaminant impacts in the vicinity of coral reefs

Coral reef communities can be deleteriously affected by exposure to low levels of anthropogenic contaminants. Sediments in the vicinity of coral reefs serve as a sink (and when resuspended, as a source) for contaminants and provide an integrative measure of low and intermittent exposure. Sediment porewater toxicity tests using gametes and embryos of the sea urchin Arbacia punctulata were employed to provide a measure of the presence of bioavailable contaminants. As sediments are patchy and composed predominately of sand in reef areas, sediment samples were collected by divers using hand cores. The utility of this approach was assessed at coral reef sites in Hawaii and southeastern Mexico. Toxicity was observed at several reef sites off Waikiki Beach in Honolulu, Hawaii and at the Sian Ka'an Biosphere Reserve in Quintana Roo, Mexico. The results of these studies have demonstrated that porewater toxicity tests are sensitive enough to differentiate among sediments with low to moderate levels of contamination and would be a valuable tool for assessing and monitoring contaminant exposure in coral reef ecosystems.