Fish “crucial” in ocean carbon cycle

Fish may play a more vital role in the marine carbon cycle than previously thought, the British journal Nature reported. A research team has found that bony fish excrete great amounts of calcium carbonate -- a discovery that may help explain why surface ocean waters are less acidic than scientific models have predicted.


Published in the American journal Science, “this is the first study that has even tried to link carbonate production by fish to global carbon cycles,” said Rod Wilson, a fish physiologist at Britain’s University of Exeter.

Biologists knew that bony fish – which most fish are — produced calcium carbonate in their guts to rid themselves of excess calcium ingested from seawater. The process had not been factored into ocean-chemistry models, however.


Wilson and colleagues from the United Kingdom, the United States and Canada sought to estimate what role fish played in global marine carbonate production. They determined that bony fish produce 40 million to 110 million tonnes of calcium carbonate per year – 3% to 15% of the estimated total of fish biomass. Carbonate produced by fish contains magnesium, an impurity that causes the mineral to dissolve more readily, thereby reducing the water’s acidity.

The new laboratory results can be extrapolated to global fish populations, Wilson says, because the predictions are based on well-studied links between fish metabolism, mass, activity level and temperature. However, he added, the calcium-carbonate production estimate is conservative and could be as high as 45%.


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