Thursday, December 07, 2006
Santa Barbara, California: - Alarming new satellite data show that the warming of the world's oceans is reducing ocean life while contributing to increased global warming.
The ocean's food chain is based upon the growth of billions upon billions of microscopic plants. New satellite data show that ocean warming is reducing these plants - thus imperiling ocean fisheries and marine life, according to an article in the November 7 issue of the scientific journal Nature.
"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," said David Siegel (homepage), co-author and professor of marine science in the Department of Geography at the University of California, Santa Barbara. Siegel is also director of the Institute for Computational Earth System Science (ICESS).
"Phytoplankton grow faster in a cool ocean and slower in a warm one," said Siegel. "The scary part is that the oceans are warming now - probably caused by our emissions of greenhouse gases like carbon dioxide."
These microscopic plants are predicted to grow even slower in the warmer oceans of the future. This in turn will reduce the food available to fish and other organisms, including marine birds and mammals, which are supported by the ocean’s food chain. Phytoplankton are responsible for about the same amount of photosynthesis each year as all the plants on land combined.
Based on the Letter to Nature "Climate-driven trends in contemporary ocean productivity":
First Paragraph (Full text is also currently available from this link):
Contributing roughly half of the biosphere's net primary production (NPP), photosynthesis by oceanic phytoplankton is a vital link in the cycling of carbon between living and inorganic stocks. Each day, more than a hundred million tons of carbon in the form of CO2 are fixed into organic material by these ubiquitous, microscopic plants of the upper ocean, and each day a similar amount of organic carbon is transferred into marine ecosystems by sinking and grazing. The distribution of phytoplankton biomass and NPP is defined by the availability of light and nutrients (nitrogen, phosphate, iron). These growth-limiting factors are in turn regulated by physical processes of ocean circulation, mixed-layer dynamics, upwelling, atmospheric dust deposition, and the solar cycle. Satellite measurements of ocean colour provide a means of quantifying ocean productivity on a global scale and linking its variability to environmental factors. Here we describe global ocean NPP changes detected from space over the past decade. The period is dominated by an initial increase in NPP of 1,930 teragrams of carbon a year (Tg C yr-1), followed by a prolonged decrease averaging 190 Tg C yr-1. These trends are driven by changes occurring in the expansive stratified low-latitude oceans and are tightly coupled to coincident climate variability. This link between the physical environment and ocean biology functions through changes in upper-ocean temperature and stratification, which influence the availability of nutrients for phytoplankton growth. The observed reductions in ocean productivity during the recent post-1999 warming period provide insight on how future climate change can alter marine food webs.
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