Plankton are able to thrive in acidic oceans

London, April 19 : Scientists have discovered that some plankton can thrive in acidic oceans, which are a result of increased levels of carbon dioxide.

According to a report in New Scientist, this was discovered by Debora Iglesias-Rodriguez from the National Oceanography Centre at the University of Southampton, UK, and her colleagues.

Most life in the ocean will suffer as carbon dioxide levels increase and the water becomes more acidic. Some plankton will buck the trend, however, thriving and putting on weight as carbon dioxide levels rise.

Evidence in support of this hypothesis was gathered by Rodriguez and her colleagues when they simulated the increase in dissolved carbon dioxide in surface ocean waters by bubbling carbon dioxide through cultures of coccolithophores, a type of single-celled photosynthesising plankton.

In previous experiments, water acidity had been regulated by simply adding acid or base, but this method has been criticised for being too artificial.

Rodriguez's method found that higher carbon dioxide concentrations increased calcification, speeding up growth of the tiny calcite plates on the plankton cell.

Coccolithophores appear to benefit in two ways.

The extra carbon dioxide aids photosynthesis, while the more acidic waters increase the concentration of bicarbonate - the main ingredient for coccolith plates, known as liths.

Making the liths results in the release of carbon dioxide, but when dead plankton fall to the ocean floor, the carbon in the shells is locked away in deep ocean chalk deposits.

"Increased bicarbonate appears to stimulate an increase in mass of calcium carbonate produced by each coccolithophore cell," said Paul Halloran, a co-author from the University of Oxford.

The team's result is not confined to the lab.

By studying fossil coccolithophores from a deep ocean core, they found that there has been a 40% increase in average coccolith mass over the last 220 years, mirroring the rise in carbon dioxide levels.

Other scientists think the results make sense and help to explain how coccolithophores survived the last rapid global warming event - the Palaeocene-Eocene thermal maximum 56 million years ago.

"Coccolithophores seemed to sail through the surface water acidification then, so perhaps they are quite insensitive to this kind of change," said Paul Bown from University College London.

ANI