delware environmental institute

NSF: Ocean acidification a culprit in commercial shellfish hatcheries' failures

The mortality of larval Pacific oysters in Northwest hatcheries has been linked to ocean acidification. Yet the rate of increase in carbon dioxide in the atmosphere and the decrease of pH in near-shore waters have been questioned as being severe enough to cause the die-offs. Now, a new study of Pacific oyster and Mediterranean mussel larvae found that the earliest larval stages are sensitive to saturation state, rather than carbon dioxide (CO2) or pH (acidity) per se.

Saturation state is a measure of how corrosive seawater is to the calcium carbonate shells made by bivalve larvae, and how easy it is for larvae to produce their shells. A lower saturation rate is associated with more corrosive seawater.

Increasing CO2 lowers saturation state, the researchers say, and saturation state is very sensitive to CO2.

The scientists used unique chemical manipulations of seawater to identify the sensitivity of saturation state for larval bivalves such as mussels and oysters.

Results of the study, which was funded by the National Science Foundation (NSF), are reported this week in the journal Nature Climate Change.