West Coast Estuaries: National Coastal Condition Assessment 2015

Setting

The West Coast region extends from the Salish Sea in Washington State, south to the California border with Mexico. The provinces of this region are the Columbian Province, which extends from the US-Canada Border into Northern California, and the Californian Province,  which goes from Northern California to the Mexico Border. The total area of the West Coast’s 410 estuaries, bays, and sub-estuaries is about 2,200 square miles. More than 60% of this area is within three large estuarine systems—the San Francisco Estuary, Columbia River Estuary, and Puget Sound (including the Strait of Juan de Fuca). Sub-estuary systems associated with these large systems make up another 27% of the West Coast. The remaining West Coast waterbodies, combined, compose only 12% of the total coastal area of the region.

There are major transitions in the distribution of human population along the West Coast, with increased population density occurring in the Seattle–Tacoma area of Puget Sound, around San Francisco Bay, and generally around most of the coastal waters of southern California. In contrast, the section of coastline north of the San Francisco Bay through northern Puget Sound has a much lower population density. With the exception of Del Norte County, California, the populations of all coastal shoreline counties on the West coast grew from 2010 to 2020 and the aggregated growth rate of West coast shoreline counties exceeded 6%¹.

Biological Condition

The NCCA found that in 2015, biological condition was good in 85% of the estuaries of the West Coast, according to the M-AMBI marine benthic index. This is better than the overall national estimate of estuaries in good biological condition of 71% and is a statistically significant increase over the proportion of West Coast area rated good in 2010. Care must be taken in interpreting these results because from 2010 to 2020, there was also a statistically significant decrease in unassessed area.

Eutrophication Index

The eutrophication index, which examines the potential for estuarine area to undergo social eutrophication based upon measurements of nutrients, chlorophyll a, dissolved oxygen and water clarity, found that 76% of West Coast estuarine area was in good condition, 19% of area was in fair condition and 5% in poor condition. This indicates that the estuarine area in the West is less likely to experience eutrophication than the country as a whole. While this is a slight improvement, the condition in 2015 doesn’t represent a statistically significant change since 2010. Continued monitoring of West Coast will help to determine if nutrient management efforts lead to improved conditions in the region.

Sediment Quality Index

About 67% of West Coast estuarine area had good sediment quality based on measures of chemical contaminants found in sediments and laboratory tests of toxicity. While this is lower than the overall estuarine area in the continental US in 2015, it shows statistically significant increase in area (by 34%) over the NCCA results for sediment quality in the West Coast in 2010. West Coast estuarine area rated fair for sediment remained steady since 2010, while area rated poor and not assessed both declined by statistically significant amounts. Continued attempts to improve sediment sample collection in West Coast estuaries will help to determine whether the increase in area rated good represents true improvements in sediment quality in the region.

Ecological Fish Tissue Contaminants

Ecological fish tissue contamination was degraded in estuaries of the West Coast in 2015 with only 25% of the area rated good and area rated fair and poor both at 24%. However, a closer look at the data reveals that the area of the West Coast that is not assessed (area for which fish suitable for analysis could not be caught) is 28%. Care must be taken when comparing populations when the unassessed area is greater than each of the assessed conditions. The NCCA is looking at way to improve sampling success in areas where fish were difficult to collect. It is important to note that this assessment of potential for adverse effects applies only to wildlife that eat fish and does not apply to people.

Human Health Indicators

More than 99% of West Coast estuarine waters have low levels of bacteria and microcystin and are safe for recreation.

Because field crews were unable to catch fish that were suitable for human consumption, 54% of the estuarine area in the West Coast was unassessed for mercury contamination in fish fillet plug samples; no estimate of area with mercury contamination either above or below the 300 parts per billion human health consumption benchmark is available for that proportion of the West Coast. Less than 1% of West Coast estuarine area have fish with concentrations of mercury in fillet plug samples exceeding the human health benchmark while fish from 46% of the area posed little to no risk for human consumption. In order to address the large proportion of area that was unassessed, the NCCA implemented new fish fillet plug sampling procedures in 2020.

A fish fillet “plug” is a small biopsy sample taken from a live fish. The fish is released after sampling.

PCBs and PFOS in whole fish fillets were only assessed in Great Lakes nearshore waters.

Recreational anglers should consult local fish consumption advisories before eating their catch.

To access more indicator graphics please visit the interactive NCCA dashboard.​

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