Siegel Coauthors Major "Nature" Article

Professor David Siegel, professor of marine science in the Department of Geography and director of the Institute for Computational Earth System Science (ICESS), is a coauthor of a major article about climate warming in the current issue of Nature. “Climate Warming Reduces Ocean Food Supply” concludes that global warming leads to a corresponding reduction in phytoplankton, creating a potential threat to fisheries and ecosystems. In the UCSB press release, Professor Siegel states: “We show on a global scale that the growth of these plants, called phytoplankton, is strongly tied to changes in the warming of the ocean. Phytoplankton grow faster in a cool ocean and slower in a warm one. The scary part is that the oceans are warming now – probably caused by our emissions of greenhouse gases, like carbon dioxide.” (

The NASA press release, featured on the front page of its Dec. 13 web site (, states:

In a NASA study, scientists have concluded that when Earth’s climate warms, there is a reduction in the ocean’s primary food supply. This poses a potential threat to fisheries and ecosystems.By comparing nearly a decade of global ocean satellite data with several records of Earth’s changing climate, scientists found that whenever climate temperatures warmed, marine plant life in the form of microscopic phytoplankton declined. Whenever climate temperatures cooled, marine plant life became more vigorous or productive.The results provide a preview of what could happen to ocean biology in the future if Earth’s climate warms as the result of increasing levels of greenhouse gases in the atmosphere. “The evidence is pretty clear that the Earth’s climate is changing dramatically, and in this NASA research we see a specific consequence of that change,” said oceanographer Gene Carl Feldman of NASA’s Goddard Space Flight Center, Greenbelt. Md. “It is only by understanding how climate and life on Earth are linked that we can realistically hope to predict how the Earth will be able to support life in the future.” Feldman is a co-author on the study, which was published this week in Nature.Phytoplankton are microscopic plants living in the upper sunlit layer of the ocean. They are responsible for approximately the same amount of photosynthesis each year as all land plants combined. Changes in phytoplankton growth and photosynthesis influence fishery yields, marine bird populations and the amount of carbon dioxide the oceans remove from the atmosphere.”Rising levels of carbon dioxide in the atmosphere play a big part in global warming,” said lead author Michael Behrenfeld of Oregon State University, Corvallis. “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.”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.The uninterrupted nine-year record shows in great detail the ups and downs of marine biological activity or productivity from month to month and year to year. Captured at the start of this data record was a major, rapid rebound in ocean biological activity after a major El Niño event. El Niño and La Niña are major warming or cooling events, respectively, that occur approximately every 3-7 years in the eastern Pacific Ocean and are known to change weather patterns around the world.Ocean plant growth increased from 1997 to 1999 as the climate cooled during one of the strongest El Niño to La Niña transitions on record. Since 1999, the climate has been in a period of warming that has seen the health of ocean plants diminish.

Behrenfeld, M. J., O’Malley, R. T., Siegel, D. A., McClain, C. R., Sarmiento, J. L., Feldman, G. C., et al. (2006). Climate-driven trends in contemporary ocean productivity. Nature, 444, 752-755. For a pdf of the complete article, click here.

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