A Probabilistic Assessment of Condition of West Coast Estuaries: Results from the National Coastal Assessment 1999-2000

Walter G. Nelson, Henry Lee II, Janet O. Lamberson

U.S. Environmental Protection Agency, Newport, OR, USA

As part of the National Coastal Assessment, the Environmental Monitoring and Assessment Program of EPA is conducting a six year evaluation of benthic habitat condition for coastal waters of the western U.S. In 1999, probabilistic sampling for a range of biotic and abiotic condition indicators was conducted at 210 stations within the small estuary systems of Washington, Oregon and California. In 2000 an additional 171 stations were sampled in Puget Sound, the Columbia River, and San Francisco Bay. Results indicate that only a small percentage of the total area of these estuarine systems has levels of sediment contamination of either metals or organic compounds potentially toxic to benthic organisms. There was also a general absence of elevated mortality in sediment bioassays conducted with the amphipod Ampelisca abdita. Nonindigenous species were present at many sample sites and were the numerical dominants at several, but overall constituted only a relatively small percentage of the total fauna other than in San Francisco Bay. Within the Western estuaries, nonindigenous species may be a more spatially widespread form of disturbance to benthic communities than sediment chemical contaminants, although the relative severity of impacts is not yet known.

Keywords: west coast estuaries, assessment, benthic condition, water quality, sediment contamination, nonindigenous species