Results of a Puget Sound water chemistry study released last week by state and federal scientists confirmed what shellfish growers already fear: The water is turning more acidic.
The study showed that water in Puget Sound’s main basin is a victim of ocean acidification, which is caused by the ocean absorbing carbon dioxide originally spewed into the atmosphere from such sources as power plants, industry and vehicles and other human activity.
Acidic marine waters are a growing threat to shellfish and the commercial shellfish industry. It’s likely that ocean acidification is contributing to the recent high mortality rates in Northwest oyster hatcheries, and the collapse of wild oyster reproduction in recent years off the Washington coast.
Hood Canal, a critical commercial shellfish growing area, showed even lower pH levels than Puget Sound’s main basin, according to the study team.
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The study was sponsored by NOAA, the University of Washington Applied Physics Laboratory and School of Oceanography, the state Department of Ecology and the U.S. Environmental Protection Agency.
It was the first study of ocean acidification in a large estuary such as Puget Sound.
The foreboding results come as no surprise to commercial shellfish growers, which have been sounding the alarm for the past three years about the threats posed by corrosive seawater caused by greenhouse gases.
“The lack of oyster seed is leading to greatly reduced populations of these critical keystone species, which portends dire consequences up and down the entire food chain,” noted a January 2009 white paper prepared for Congress by the Pacific Coast Shellfish Growers Association.
Even if the nation, and the rest of the world, got serious about curbing carbon dioxide emissions, acidification rates are expected to continue to grow for years, the scientists said.
Oyster larvae are particularly vulnerable to acidic water. Shortly after they are born, their developing shell consists of a weak, soluble mineral called aragonite. Aragonite is especially sensitive to pH levels. Even a slight lowering of pH can prevent the shells from developing.
The threat of corrosive water is forcing shellfish growers to closely monitor saltwater intake at their hatcheries in search of water with lower pH levels at different depths and times of day.
Meanwhile, to better understand how ocean acidification is impacting Puget Sound shellfish, the Puget Sound Partnership and Puget Sound Restoration fund is working with scientists and the shellfish industry to study the relationship between shellfish larvae and water chemistry at two locations where shellfish are growing — Dabob Bay in Hood Canal and Totten Inlet in South Sound.
The studies are critical, but action to reduce concentrations of carbon dioxide in the atmosphere and in the ocean are even more so.