evelopment of Sediment Quality Objectives for California's Enclosed Bays and Estuaries: Fid-Bau Portal

evelopment of Sediment Quality Objectives for California's Enclosed Bays and Estuaries

Beegan, Chris

Sediments in bays and estuaries are often contaminated with a variety of pollutants as a result of industrial and agricultural discharges, municipal wastewater treatment plants and other point and nonpoint source discharges. Exposure to contaminated sediments can have a significant effect on the health, diversity and abundance of benthic invertebrates such as clams and worms that live within and on the sediment. Fish and birds foraging on benthic invertebrates may also be exposed through ingestion of benthic invertebrates and sediment. Animals in higher trophic levels can also be exposed to bioaccumulative pollutants by eating contaminated fish. These effects underscore the necessity of developing sediment quality objectives for the protection of both marine and terrestrial ecosystems and human health and welfare. Sediment quality objectives are defined in the California Water Code as the "level of a constituent in sediment, which is established, with an adequate margin of safety for the reasonable protection of beneficial uses of water or prevention of nuisances." The current effort proposed by the State Water Resources Control Board to develop sediment quality objectives focuses on evaluating the risk to benthic organisms under the assumption that by protecting these communities, higher trophic levels will also be protected. Although this assumption is somewhat simplistic, many of the tools that have been developed for assessing sediment quality are based on the effects on benthic invertebrates; either through sediment toxicity testing or benthic community assessments that evaluate structure, diversity and abundance. Benthic invertebrates are considered excellent indicators of sediment quality because they exhibit low mobility and are directly exposed for relatively long durations. While benthic invertebrates can be useful as indicators, evaluation of benthic conditions is difficult due to a high degree of variability that exists for the following reasons: 1) Biological response is dependent upon both the individual organism health and sensitivity and the bioavailability of the contaminants. Neither factor is well understood. 2) Benthic community structure can also exhibit a high degree of seasonal and temporal variability. 3) Other confounding factors include the presence of opportunistic nonindigenous species that can have a profound effect on community makeup and structure. 4) Sediment toxicity test results can be influenced by other factors not directly related to in situ bioavailability, such as sample manipulation and disturbance. The State Water Resources Control Board will also evaluate the development of chemical-specific sediment quality criteria. There are several different methods for developing chemical specific sediment quality guidelines have been used successfully to evaluate dredged materials and to prioritize remedial efforts throughout the nation. Empirical approaches include the Apparent Effects Threshold (AET) Approach and the Effects Range (ER) Approach.