Publication Summary

The Marine Sediment Monitoring Program (MSMP) was implemented in 1989 to characterize baseline sediment quality conditions and trends throughout Puget Sound. The MSMP has adopted the Triad approach to sediment monitoring. Components of the Triad are the measurement of sediment contaminants, the evaluation of biological conditions, and the assessment of potential for sediment toxicity. Individually, the components of the Triad do not provide for an adequate understanding of sediment quality. In combination, the biological significance of actual and potential contaminant levels can be assessed by analysis of benthic community structure and toxicity in laboratory bioassays.

The Appendices are linked as a separate file.

The Marine Sediment Monitoring Program (MSMP) was implemented in 1989 to characterize baseline sediment quality conditions and trends throughout Puget Sound. The MSMP has adopted the Triad approach to sediment monitoring. Components of the Triad are the measurement of sediment contaminants, the evaluation of biological conditions, and the assessment of potential for sediment toxicity. Individually, the components of the Triad do not provide for an adequate understanding of sediment quality. In combination, the biological significance of actual and potential contaminant levels can be assessed by analysis of benthic community structure and toxicity in laboratory bioassays.

Data were collected annually from 1989-1995. Eighty-six stations were established throughout Puget Sound, Hood Canal, the Strait of Georgia, and the Strait of Juan de Fuca. Locations included centers of major basins, bays and inlets, shallow subtidal areas, and historic sampling sites. Stations were grouped in two categories: core stations sampled annually, and rotating stations sampled once every three years alternating between North, Central and South Puget Sound regions. At each station, replicate sediment samples were collected for the analysis of chemical contaminants, sediment variables, and benthic community structure. In addition, sediments from each station were tested in laboratory bioassays for toxicity to the amphipod Rhepoxynius abronius. This volume addresses the chemistry and toxicity testing portions of the MSMP. Volume 2 presents results of benthic community analysis.

Overall, contaminant concentrations at monitoring stations were generally low and below sediment quality standards. Of five chemical groups (metals, VOC, ABN, PCB, pesticides) analyzed for, metals and semi-volatile organic compounds were most frequently detected. The highest metal and organic contamination was found in locations associated with urban and industrial centers. Low metal concentrations were also detected in some rural areas and in deep depositional environments. Contaminant concentrations occasionally exceeded regulatory sediment quality standards. However, there was no consistent pattern across years. A notable exception was mercury in Sinclair Inlet and Dyes Inlet, with concentrations above standards for each of the seven years monitored.

Amphipod bioassay results indicated significant mortality in both rural and urban stations. Mortality from seven samples could be attributed to chemical toxicity, but there was no consistent pattern across years. Sulfides in sediments of Puget Sound were primarily associated with areas where restricted water circulation and density stratification may contribute to low dissolved oxygen episodes.

Because the range of contaminant concentrations was generally low and did not reflect spatial conditions at urban bays, we recommend a comprehensive approach that investigates both ambient sediments and gradients of pollution near sources. Since sediment chemistry reflect multi-year deposition, we recommend that the sampling frequency of contaminants be reduced. Additionally, we recommend the use of alternative sediment bioassays as screening tools, and support of research on the source, transport, and fate of contaminants in Puget Sound.