Global warming harms world's ocean food chain
www.chinaview.cn 2006-12-07 10:17:21

    BEIJING, Dec. 7 (Xinhuanet) -- New satellite data show the vital base of the ocean food chain -- hytoplankton --decreases when the world's seas warm up and that has scientists worried about how much food marine life as oceans become warmer because of global warming.

    The data show a significant link between warmer water -- either from the El Nino weather phenomenon or global warming -- and reduced production of phytoplankton, according to a study in Thursday's journal Nature.

    Phytoplankton are the microscopic plant life that zooplankton and other marine animals eat, essentially the grain crop of the world's oceans.

    Study lead author Michael Behrenfeld, a biological oceanographer at Oregon State University, said Wednesday the recent dplunge in phytoplankton production in much of the world's oceans is a "sneak peak of how ocean biology" will respond later in the century with global warming.

    A satellite commissioned by NASA recorded water temperature and phytoplankton production from 1997 to 2006. It revealed that for most of the world's oceans when increased the other decreased and vice versa, Behrenfeld said.

    As water temperatures rose from 1999 to 2004, the crop of phytoplankton dropped significantly, about 200 million tons a year. On average about 50 billion tons of phytoplankton are produced yearly, Behrenfeld said.

    "Everything else up the food web is going to be impacted," said oceanographer Scott Doney of the Woods Hole Oceanographic Institute, who was not involved in the study. "What's worrisome is that small changes that happen in the bottom of the food web can have dramatic changes to certain species at higher spots on the food chain."

    This is yet another recent scientific study with real-time data showing the much predicted harmful effects of global warming are not just coming, but in some cases are already here and can be tallied scientifically, researchers said.

    When the satellite first started taking measurements in 1997 water temperatures were at their warmest because of El Nino, a warming of part of the Pacific Ocean that affects climate worldwide.

    After that year, the ocean significantly cooled until 1999 and the phytoplankton crop soared by 2 billion tons during those two years.

    "The results are showing this very tight coupling between production and climate," Behrenfeld said.

    Phytoplankton, which turn sunlight into food, need nutrients such as nitrogen, phosphates and iron from colder water below, Behrenfeld said. With warmer surface water, it is harder for the phytoplankton to get those nutrients.

    Another worry is with reduced phytoplankton, the world's oceans will absorb less carbon dioxide and increase Earth's primary global warming gas, said NASA ocean biology project manager Paula Bontempi. That's because phytoplankton take carbon dioxide out of the atmosphere in making food.

    (Agencies)

Editor: Gareth Dodd
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