Saturday, March 2, 2013

New study reveals how sensitive US east coast regions may be to ocean acidification

Science Daily: A continental-scale chemical survey in the waters of the eastern U.S. and Gulf of Mexico is helping researchers determine how distinct bodies of water will resist changes in acidity. The study, which measures varying levels of carbon dioxide (CO2) and other forms of carbon in the ocean, was conducted by scientists from 11 institutions across the U.S. and was published in the journal Limnology and Oceanography.

"Before now, we haven't had a very clear picture of acidification status on the east coast of the U.S.," says Zhaohui 'Aleck' Wang, the study's lead author and a chemical oceanographer at Woods Hole Oceanographic Institution (WHOI). "It's important that we start to understand it, because increase in ocean acidity could deeply affect marine life along the coast and has important implications for people who rely on aquaculture and fisheries both commercially and recreationally."

Coastal ocean acidification, Wang says, can occur when excess carbon dioxide is absorbed by, flushed into or generated in coastal waters, setting off a chain of chemical reactions that lowers the water's pH, making it more acidic. The process disproportionately affects species like oysters, snails, pteropods, and coral, since those organisms cannot effectively form shells in a more acidic environment.

...Since the waters of the northeast U.S. are already susceptible to rising acidity, Wang says this raises big questions about how species of marine life -- many of which are important to the commercial fishing and shellfish industry there -- will fare in the future. "For example, how are oysters going to do? What about other shellfish? If the food chain changes, how are fish going to be impacted?" Wang asks. "There's a whole range of ecological and sociological questions." There is a great need for need for more robust coastal ocean chemistry monitoring and coastal ocean acidification studies, he adds. A better understanding of the changing chemistry will help fisheries regulators to better manage the stocks....

By collecting and analyzing water samples, Wang and his colleagues charted the coastal ocean’s capacity to buffer itself from increase input of CO2or resist a change in pH (shown as a ratio of total alkalinity, TA, to dissolved inorganic carbon, DIC). The dark blue color indicates a low capacity; red indicates a higher capacity. The waters in the Gulf of Mexico are more resistant to change; the waters off New Hampshire and Massachusetts are less resistant. In the figure, the contour lines labeled with numbers represent the calcium carbonate saturation state of aragonite, a mineral form of calcium carbonate. The higher numbers mean shell-building organisms have more carbonate with which produce their shells than areas with lower numbers, where less carbonate is available for shell building. Shells will dissolve in waters with a saturation state value below 1, but organisms will feel the effect of low saturation state before it reaches 1. (Credit: Courtesy Wang, et al., 2013)

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