Plankton blooms off New Zealand leave track of ocean warming: study

White blooms of plankton have drifted southwards, indicating the oceans is responding to global climate change, according to a New Zealand study out Monday.

Under favorable, warm conditions, algae known as coccolithophores grew rapidly and turned the ocean's surface milky white when they bloomed, leaving remains known as coccoliths, said Victoria University researcher Bella Duncan.

Satellite and ship-based observations showed coccolith blooms were moving south as the ocean warmed and became less turbulent, similar to the way it did around 130,000 years ago when the last major warm period occurred.

Coccoliths were deposited on the ocean floor and formed white mud similar to the White Cliffs of Dover, the iconic natural landmark in Britain that was also formed during a previous warm period about 70 million years ago.

"Our results show that during that last warm period, when the ocean was about 1 to 2 degrees (centigrade) warmer than present, sediments on the seabed were mainly made up of coccoliths," Duncan said in a statement.

The research team examined cores of sediment from sub-Antarctic waters on the vast Campbell Plateau south of New Zealand, and used a laser-based method to determine the presence of coccoliths.

"In a 2-meter core you have a 200,000-year-old record of sediment deposition. We took samples at frequent, regularly-spaced intervals down the cores to gain an insight into coccolith production in the past," said Duncan.

The phenomenon suggested the New Zealand ocean was responding the present phase of global warming a trend increasingly observed in other parts of the world, Professor Lionel Carter said in the statement.

"While the ramifications of this change on fish stocks, uptake of carbon dioxide and general ocean health have yet to be evaluated, it is clear that change is underway," said Carter. Endit