WASHINGTON -- In a "sneak peak" revealing a grim side effect of future warmer seas, new NASA satellite data found that the vital base of the ocean food web shrank as the world's seas got warmer.
The discovery has scientists worried about how much food marine life will have as global warming progresses.
The data show a significant link between warmer water -- either from the El Niño weather phenomenon, or global warming -- and a reduced production of phytoplankton of the world's oceans, according to a study in today'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 yesterday that the recent dramatic drop 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.
"Everything else up the food web is going to be impacted," said oceanographer Scott Doney of the Woods Hole Oceanographic Institute in Massachusetts . He 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," Doney said.
This is yet another recent scientific study with real-time data showing that the much-predicted harmful effects of global warming are, in some cases, already here, researchers said.
A satellite commissioned by the National Aeronautics and Space Administration tracked water temperature and the production of phytoplankton from 1997 to 2006, finding that for most of the world's oceans, when one went up, the other went down and vice versa, Behrenfeld said.
As water temperatures increased 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.
However, the satellite first started taking measurements in 1997, when water temperatures were at their warmest because of El Niño, the regular cyclical warming of part of the Pacific Ocean.
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.
Other oceanographers agree that an El Niño link exists but said that with only a decade of data it is harder to make global warming connections.