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article imageAcid seas hit commercial shellfish production

By Tim Sandle     Dec 23, 2014 in Environment
Scientists have discovered that larval oysters and mussels are sensitive to reduced pH. This is due to rising levels of acidity in the world’s oceans.
Climate change has been affecting commercial oyster and mussel growers for several years. However, scientists were not sure how rising carbon dioxide levels and the resultant ocean acidification (reduced pH) harmed the farmed bivalves.
Now a new theory has been proposed: saturation state. In a new paper, scientists from Oregon State University have reported that the larvae of Pacific oysters and Mediterranean mussels have a difficult time forming their calcium carbonate shells as the surrounding seawater’s saturation state falls. Saturation state is a measure of how corrosive the seawater is to the shells that the larvae make as they grow, and as carbon dioxide increases in the atmosphere, saturation state drops. A lower saturation state means more corrosive water.
Discussing the research further, David Garrison, program director in the US National Science Foundation’s Division of Ocean Sciences, said in a research note: “Biological oceanographers have speculated that early life stages of marine organisms might be particularly sensitive to ocean acidification, but the underlying mechanisms remain unknown for most species.
“This research is an important step in being able to predict, and perhaps mitigate, the effects of ocean acidification on coastal resources.”
To test out the theory, researchers exposed shellfish larvae to chemically manipulated seawater in a laboratory and tracked the effects of falling saturation state on their growth. They found that if water was too acidic, the free-swimming larvae had to expend too much energy on shell growth, which diverted energy from feeding and swimming activities. This was especially damaging because the developing mollusks have a brief, 48-hour window in which they must begin feeding at a rate that ensures their survival.
In the commercial world, hatcheries call this ‘lazy larvae syndrome.’ This is because these tiny oysters just sink in the water and stop swimming.
It would seem that shellfish are very sensitive windows to ocean acidification. The findings have been published in the journal Nature Climate Change. The research is headed “Saturation-state sensitivity of marine bivalve larvae to ocean acidification.”
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