Sydney: Climate change and acidification of oceans will significantly reduce the reproductivity of certain marine species by 2100, a team of biologists has warned.

A Macquarie University team led by Anne Williamson joined forces with the University of Gothenburg (Sweden) to study the effects of acidification on sea urchin fertility, finding a link between decreased pH (increased acid) levels and a reduction in sperm swimming speed and motility.

"What we have now is evidence that the world's marine life is far more sensitive to ocean acidification than first suspected, and that means our oceans may be very different places in the not too distant future," Williamson said.

She said sea urchin gametes and larvae used in the research were exposed to the same acid levels that are predicted to be present in the world's oceans by the year 2100.

The surface of the ocean absorbs up to 30 percent of the yearly emissions of carbon dioxide. This absorbed gas dissolves in the water and forms a weak acid that is gradually increasing the acidity of the oceans.

"It is widely believed that seawater is chemically well-buffered, but these results show that the acidification process already well underway may threaten the viability of many marine species," Williamson said.

"Our results show that carbon dioxide-induced acidification of seawater, at levels predicted for the year 2100, reduced fertilisation success of an ecologically dominant marine species by 25 percent."

The Macquarie University study is especially significant, as equivalent results have only previously been found at far more extreme levels of acidification.

Heliocidaris erythrogramma species is found commonly in inshore waters around south-eastern Australia.

These findings were published in Tuesday's issue of Current Biology. IANS