January 28, 2009

Climate change may expand ocean dead zones

Danish scientists are warning that uncontrolled global warming might significantly expand the ocean's dead zones, seriously affecting fish and shellfish.

Dead zones are low-oxygen areas in the ocean where higher life forms such as fish, crabs and clams are not able to live, the University of Copenhagen researchers said. In shallow coastal regions, such zones can be caused by runoff of excess fertilizers from farming.

Professor Gary Shaffer, who led the study, said unchecked global warming would lead to a dramatic expansion of low-oxygen areas zones in the global ocean by a factor of 10 or more.

The scientists said although some coastal dead zones could be recovered by controling fertilizer usage, expanded low-oxygen areas caused by global warming will remain for thousands of years, adversely affecting fisheries and ocean ecosystems far into the future.

Such expansion would lead to increased frequency and severity of fish and shellfish mortality events, for example off the west coasts of the continents like off Oregon and Chile, said Shaffer.

The findings are reported in the journal Nature Geoscience.