Not plenty of fish in the ocean due to global warming

Stan Beer
Thursday, 07 December 2006 18:24

Science - Climate

A new NASA study has found that the food supply of fish and other life in the ocean is diminishing as a result of global warming. The results of the study is based on correlating satellite data with records of the change in Earth's climate over the past nine years.

For the two years between 1997 and 1999, the Earth's climate cooled as it transitioned out of an El Nino event and the microsocopic marine plant life known as phytoplankton near the surface of the oceans increased. However, since 1999 there has been continual global warming and a corresponding decrease in phytoplankton.

The findings are from a NASA-funded analysis of data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument on the OrbView-2 spacecraft, launched in 1997. SeaWiFS is jointly operated by GeoEYE, Dulles, Va. and NASA.

The effect of a reduction of phytoplankton on the Earth's ecosystem has serious consequences for two major reasons. First, phytoplankton are the primary source of nutrients for the oceanic food chain which includes fish and the marine birds that feed off them. Second, phytoplankton play a similar and approximately equal role to land based plant life in the process of photosynthesis, which converts sunlight and nutrients into chlorophyll and removes carbon dioxide, the principle cause of global warming, from the atmosphere.

The effect of a reduction in phytoplankton therefore means less for fish to feed, less carbon dioxide removed from the atmosphere and increased global warming. The warming of the oceans near the surface creates a barrier between the warm surface and colder lower regions, which cuts of the access of phytoplankton to essential nutrients below that they need to flourish.

"Rising levels of carbon dioxide in the atmosphere play a big part in global warming," said Michael Behrenfeld of Oregon State University, Corvallis, who was lead author of the study which appears in the scientific journal Nature today. "This study shows that as the climate warms, phytoplankton growth rates go down and along with them the amount of carbon dioxide these ocean plants consume. That allows carbon dioxide to accumulate more rapidly in the atmosphere, which would produce more warming."