Marine Sediment Quality

A functioning, resilient Puget Sound ecosystem is defined to include marine sediment quality that supports functioning, healthy communities of sediment-dwelling invertebrates. The sediment (gravel, sand, silt, and clay) on the floor of Puget Sound forms a unique habitat that is home to clams, marine worms, burrowing shrimp, bottom-dwelling fish, and thousands of other unique species. In turn, these animals form a critical part of the marine food web, are instrumental in mixing and oxygenating the sediments, and they process the sediments allowing nutrients to cycle between the sediments and the overlying waters.

The sediments are burdened with chemical contaminants in some locations in Puget Sound. This Vital Sign tells us about the level and toxicity of chemical contaminants in Puget Sound sediments and their ability to support the aquatic life that live in and on them. They help us understand whether efforts to reduce pollutants to marine waters are effective.


Key Messages

      Benthic marine organisms. Dep. of Ecology

  • Sediment chemistry - The majority of Puget Sound sediments sampled from 1997-2015 do not have elevated levels of measured chemical contaminants. Highest concentrations were near population and industrial centers, with improvements seen in these areas over time.
  • Sediment toxicity – 88 percent of Puget Sound sediments measured from 1997-2015 were non-toxic. Sediments with low, moderate, or high toxicity were located near urban and non-urban terminal inlets and areas with poor circulation, low dissolved oxygen, and high sulfides.
  • Benthic invertebrates – Significant declines in total abundance and taxa richness occurred in sediment-dwelling invertebrate assemblages in Puget Sound regions and bays sampled from 1997-2015. Declines were also noted for these stations grouped by harbor, urban, passage, and rural characteristics.
  • Little correspondence between measures – Statistical analyses revealed low correspondence between the sediment chemistry, toxicity, and invertebrate community characteristics measured in sediments throughout Puget Sound from 1997-2015.
  • Alternative environmental pressures – Declines occurring in invertebrate community condition despite low and declining sediment contaminant levels point to stresses from other environmental pressures, for example climate change, ocean acidification, nutrient loading, which should now be examined.

Other Resources

Contributing Partners

Margaret Dutch, Marine Sediment Monitoring Team, Washington State Department of Ecology. Key messages were reviewed by the PSEMP Toxics Work Group.
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