Status and trends in sediment toxicity in Puget Sound

Multiple sediment bioassay methods have been applied to determine the toxicity of surficial sediments in Puget Sound. Over 600 individual sediment samples have been tested for either lethality or a variety of sublethal effects. The results show that samples collected near urban areas bordering the Sound are often toxic. The toxic spots are often associated with past dumping, nearby landfills, storm drains, sewer overflows, or industrial discharges. Those sites from which the majority of the samples were toxic for over half of the types of tests were judged to be significantly toxic. These sites encompassed about 4.0 square miles of the bottom of the Sound representing about 0.2% of the total 1900 square miles of the U.S. portion of the Sound, or about 3% of the 140 square miles tested thus far. Remedial action planning has been correctly focused upon the toxic sites and adjacent sources.