5.0 Condition of the Estuary

Contents

Summary of Overall Condition

Some Estuary contaminants are clearly reduced from peak levels seen in earlier decades. Nevertheless, there are several indications that the level of contamination today is high enough to impair the health of the Estuary ecosystem. These indications include the toxicity of water and sediment samples; the frequent presence of contaminant concentrations exceeding water, sediment and fish guidelines; and altered communities of sediment dwelling organisms. As a whole, the Estuary can be described as moderately contaminated. The remedy for this contamination involves both action by Estuary managers to decrease the continuing input of contaminants and undertake sediment clean up actions where appropriate, and the passing of time, to allow the large reservoir of contaminants in the sediment to decrease naturally through permanent burial by new sediment, degradation, and transport to the ocean.

Sites of greatest concern, sites of least concern

Overall, sites in the lower South Bay, the Petaluma River mouth, and San Pablo Bay are the more contaminated than other sites. Contamination in the Central Bay is lower primarily due to mixing with relatively clean ocean water. The site west of the Golden Gate is least contaminated.

Contaminants of greatest concern

Of the contaminants measured by the RMP, results suggest that levels of mercury, PCBs, diazinon, and chlorpyrifos are of highest concern. Also of concern are copper, nickel, zinc, DDT, chlordane, dieldrin, dioxins and PAHs. Work outside the RMP suggests that selenium is also of high concern. Of unknown concern are each of the many synthetic organic contaminants that may be in the Estuary but that the RMP does not currently measure.