1. United States Department of Agriculture, Agricultural Research Service, Environmental Chemistry Laboratory, Beltsville, Maryland 20705, National Marine Fisheries Service, South East Fisheries Science Center, Charleston, South Carolina 29422-2607, Department of Chemistry and Biochemistry and Marine Science Program, University of South Carolina, Columbia, South Carolina 29208, Russian Academy of Science, Limnological Institute, Irkutsk, Russia, and Institute of Fisheries, Moscow, Russia