Publication Summary

Sediment chemistry and biota samples collected from 1989 - 2000 for the Puget Sound Ambient Monitoring Program were analyzed to establish conditions at ten monitoring stations in Puget Sound, and to identify changes occurring over time. Generally, metals concentrations in 2000 were lower than in 1989-1996, while the opposite was true of polycyclic aromatic hydrocarbons (PAHs). Grain size and benthic community changes in the Strait of Georgia were probably linked to increased precipitation, Fraser River flow, and sediment loading events. This 12-year time series provides a valuable long-term record of Puget Sound sediment conditions against which we can compare future environmental changes.

As part of the Sediment Component of the Puget Sound Ambient Monitoring Program (PSAMP), samples from ten long-term monitoring stations collected from 1989 through 2000 were summarized to establish a record of sediment conditions for a variety of habitats and geographic locations throughout Puget Sound and to identify significant changes, if any, in physical, chemical, and biological sediment parameters that have occurred over time.

Less than one-third (32%) of almost 13,000 chemical measurements made were detected during testing. Those detected most often exceeded sediment quality guidelines in urban embayments: Sinclair Inlet (mercury), Thea Foss Waterway (polycyclic aromatic hydrocarbons, or PAHs).

In general, metals concentrations in 2000 were lower than in 1989-1996 far more often than they were higher, while the opposite was true of PAHs. At the Port Gardner and Inner Budd Inlet stations, concentrations of a number of priority pollutant and ancillary metals also decreased significantly. Individual PAH levels decreased at the Point Pully station, but increased significantly at the Bellingham Bay, Port Gardner, and East Anderson Island stations. Total HPAH levels increased significantly at the Bellingham Bay and East Anderson Island stations. Total LPAH and total PAH levels increased significantly at the Strait of Georgia, Bellingham Bay, East Anderson Island, and Budd Inlet stations. These changes may reflect changes in anthropogenic input of contaminants to the estuarine system over this 12-year study period.

Additionally, changes in grain size and benthic infaunal community composition seen at the Strait of Georgia station were probably linked to increased precipitation and subsequent increased flow and sediment loading from the Fraser River in 1996 and 1997.

This 12-year time series of Puget Sound sediment data provides a vital record of the past and existing condition of sediments, and a valuable long-term perspective against which we can measure the magnitude of future environmental changes.