Scientists solve important marine puzzle

Washington, Jan 18 (ANI): An international team of scientists has solved a marine puzzle, by finding that fish contribute a significant fraction of the oceans' calcium carbonate production, which affects the delicate pH balance of seawater.

The study gives a conservative estimate of three to 15 percent of marine calcium carbonate being produced by fish, but the researchers believe it could be up to three times higher.

The findings highlight how little is known about some aspects of the marine carbon cycle, which is undergoing rapid change as a result of global CO2 emissions.

Until now, scientists believed that the oceans' calcium carbonate, which dissolves in deep waters making seawater more alkaline, came from marine plankton.

The recent findings explain how up to 15 percent of these carbonates are, in fact, excreted by fish that continuously drink calcium-rich seawater.

The ocean becomes more alkaline at much shallower depths than prior knowledge of carbonate chemistry would suggest which has puzzled oceanographers for decades.

The new findings of fish-produced calcium carbonate provides an explanation: fish produce more soluble forms of calcium carbonate, which probably dissolve more rapidly, before they sink into the deep ocean.

The researchers suggest that fish carbonates dissolve much faster than those produced by plankton, and at depths of less than 1,000 m.

Less soluble carbonates, produced by plankton, are more likely to sink further and become locked up in sediments and rocks for tens or hundreds of millions of years before being released.

Fish carbonates, on the other hand, are likely to form part of the 'fast' carbonate system by more rapidly dissolving into seawater.

"As a marine chemist who has been studying the global carbon cycle and its impacts on the pH of the water and marine ecosystems for 40+ years, these results offer an important piece of the equation," said Dr. Frank Millero from the University of Miami's Rosenstiel School of Marine and Atmospheric Science.

"By working with scientists in several disciplines we were able to come at this from different perspectives and combine data sets that hadn't been previously used together, to solve this problem. We can now employ the knowledge gained from this study to examine how ocean acidification due to the adsorption of CO2 from the burning of fossil fuels affects the ocean carbon system," he added. (ANI)