Oregon State University

Ocean Acidity

George Waldbusser

Increasing ocean acidification is a major global concern. Acidification due to anthropogenic sources can affect important shellfish such as oysters and clams, as well as other important coastal resources.

Benthic ecologist George Waldbusser studies the effect of ocean acidification on shelled animals, particularly juvenile bivalves such as  hard clams. A recent study that he led in Chesapeake Bay has found that increased acidity in certain parts of the bay is reducing rates of juvenile oyster shell formation.

“In Chesapeake Bay we see large daily and seasonal changes in pH that are related to sunlight, photosynthesis and freshwater input.” However, Waldbusser added, “we should be aware that increasing atmospheric CO2 and eutrophication appears to be shifting the baseline within these other cycles.” Off the Oregon coast, seasonal upwelling also drives changes in acidity.

According to Waldbusser, acidification in the coastal ocean and estuaries is a complex process to study. “Although post-larval hard clamspreliminary predictions on winners and losers in an acidified ocean have been based on shell mineralogy, we have an interesting system here in Oregon with introduced oysters that seem to be sensitive to seasonally acidified water and native oysters that appear much less sensitive to acidification. Both species have similar shell mineralogy, but different life history strategies.”

Waldbusser is leading a newly funded National Science Foundation project with an interdisciplinary Oregon State University project team including carbon biogeochemist Burke Hales, isotope geochemist Brian Haley, and shellfish physiologist Chris Langdon. Using their complementary expertise, the team has designed an incubator system to test how native and non-native oysters, clams, and mussels to the Pacific Northwest will respond to changes in the carbonate system.

“We’ll be developing a novel experimental approach to tease apart just what component of acidifi cation is actually affecting the organism,” Waldbusser said. “For example, decreased pH may aff ect the internal acid-base balance of an organism, but the correlated decrease in calcium carbonate saturation state may also alter the stability of their mineral shells. Scientists know very little, to date, about specific modes of action triggered by acidification.”

Waldbusser is also interested in the sustainability of oyster reefs in an acidified ocean. Built from the calcium carbonate shells of many generations of oysters, oyster reefs share some similarities to coral reefs. Oyster reefs support a diversity of other organisms, are important to larval oysters in providing larvae habitat and some refuge from predators, and healthy reefs are important to biogeochemical cycling. Waldbusser has measured dissolution rates of oyster shells from Chesapeake Bay and is working to develop a better understanding of how oyster reefs may respond to changes to acidity.

Article courtesy of the College of Earth, Ocean, and Atmospheric Sciences 2010 Research Highlights

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