The Washington State Department of Ecology has been collecting data on Puget Sound sediment-dwelling (benthic) invertebrates since 1989, as part of the Marine Sediment Monitoring Program. Benthic organisms serve key functions, including processing and storage of organic material and cycling of nutrients needed by other components of the ecosystem. Benthic invertebrates are an integral part of the marine food web and biogeochemical processes that support salmon, orcas, and humans and are a key component of the Puget Sound ecosystem. We are finding significant declines in the overall condition of benthic communities, with 44% of the study area adversely affected. Many of the adversely affected benthic communities were found in terminal inlets and bays. Throughout Puget Sound, an increase of pollution/hypoxia-tolerant species and a decrease in sensitive species has occurred over time. Deterioration of benthic communities does not correspond well with changes in individual chemical contaminants measured or laboratory tests of sediment toxicity. The spatial distribution of benthic communities is in part defined by the changing physical and oceanographic habitat. Changes in the abundance and composition of the benthic invertebrate community over time may indicate responses of the ecosystem to climatic stressors and large-scale ecological shifts such as changing hydrological, nutrient, oxygen, or acidic conditions
