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Report states sediment health in Central Puget Sound declining
OLYMPIA — Sediments in the bottom of Central Puget Sound show declining environmental health over a 10-year period, according to a just-released report from the Washington Department of Ecology (Ecology).
Central Puget Sound is the area south of Whidbey Island to the Tacoma Narrows. It includes industrialized and urbanized Elliott and Commencement bays, Sinclair Inlet and Bainbridge Basin.
“The overall decline in sediment health is important because it is an indicator of the health of Puget Sound,” said Valerie Partridge, Ecology’s lead author for the report.
The report, “Sediment Quality in Central Puget Sound, Changes Over a 10-Year Period,” compared sediment samples the state program collected in 2008 and 2009 to samples it collected in 1998 and 1999.
The comparison found the decline in health of sediment-dwelling life – known as benthic invertebrates – had spread to 28 percent of the region, up from seven percent.
Benthic invertebrates are a key part of the marine food web.
The decline could not be attributed to any significant chemical contamination that Ecology measured. The major driving factor contributing to the decline in sediment health was the change in the number and types of benthic invertebrates, including a shift to more pollution-tolerant species.
Ecology also found an increase in low-level toxicity in the sediments over a wider area compared with previous testing in Central Puget Sound.
The study also turned up good news. Central Sound sediments showed a decrease in concentrations of lead, mercury, silver, tin and polycyclic aromatic hydrocarbons. It also found that more samples are meeting state sediment quality standards in the heavily industrialized areas of Elliott and Commencement bays. These trends suggest positive results from collective cleanups and pollution prevention efforts in those areas.
Ecology scientists are not sure why the negative changes are taking place.
Maggie Dutch, lead scientist for Ecology’s Puget Sound Sediment Monitoring Program said: “The sediment monitoring program was established to measure levels of toxic chemicals throughout Puget Sound, and to determine their effects on benthic invertebrate communities. While we have seen improvements in the condition of these communities in urban areas that have undergone cleanup of toxics, we are also seeing unexpected declines in community condition where toxic chemicals we measure were not detected. Other human and natural factors in Puget Sound could be a cause.”
Dutch said some of the factors that may influence the health of the organisms in the sediments include:
• Changes in food resources that sink through the water and reach the bottom sediments.
• Changes in dissolved oxygen, pH, and levels of ammonia and sulfides in the water above and within the sediments.
• Natural population cycles of sediment-dwelling organisms that may be influenced by oceanic cycles.
• Sediment movement and burial.
• Unmeasured contaminants, including contaminants of emerging concern, contaminant mixtures, and contaminants that may sicken but not kill marine life.
Dutch said, “While we did not measure these other factors, we will link our data to other projects that may have this information to help us map out causes.”
The state’s regional sediment monitoring is part of the Puget Sound Ecosystem Monitoring Program (PSEMP). The program is a collaboration of state, federal, tribal, local government, non-governmental, watershed, business, private and volunteer groups dedicated to monitoring the environmental conditions of Puget Sound.
Ken Dzinbal, PSEMP lead for the Puget Sound Partnership, said: “Marine monitoring is important because you can’t fix what you don’t measure. Monitoring tells us if Puget Sound is getting better or if it’s getting worse.”
“We are seeing trends. We have ideas about the causes of problems. Our monitoring helps tell us if we are testing the right things and helps us identify solutions to pollution problems,” Dzinbal said.
Scientists have developed several ecological indicators to track the health of the Puget Sound ecosystem and how it changes over time. Ecology’s sediment science has been adopted by the Puget Sound Partnership as Vital Signs Dashboard Indicators.
While the Central Sound findings are for the region as a whole, Ecology’s marine monitoring program has separate surveys and separate reports for Elliott Bay, Commencement Bay and the Bainbridge Basin (including Sinclair Inlet). The stories of the bays are different from the story of the region as a whole.
Ecology has observed similar declines in benthic invertebrate health in other regions and bays throughout Puget Sound, including the Strait of Georgia, Hood Canal, Elliott Bay, Commencement Bay, and Bainbridge Basin. Poor sediment health also has been observed in Bellingham Bay, Budd Inlet, the Eastern Strait of Juan de Fuca, and the San Juan Islands.
Ecology is conducting follow-up sediment sampling in Elliott Bay. Sediment monitoring of urban bays is part of Ecology’s Urban Waters Initiative, which began in 2007.