Global Ocean Phytoplankton Declines By 6% Since 1980s - NASA

Ocean Plant Life Slows Down And Absorbs Less Carbon

"Plant life in the world's oceans has become less productive since the early 1980s, absorbing less carbon, which may in turn impact the Earth's carbon cycle, according to a study that combines NASA satellite data with NOAA surface observation of marine plants.

Microscipic ocean plants called phytoplankton account for about half the transfer of carbon dioxide (CO2) from the environment into plant cells by photosynthesis. Land plants pull in the other half. In the atmosphere, CO2 is a heat-trapping greenhouse gas.

Watson Gregg, a NASA GSFC researchers and lead author of the study, finds that the oceans' net primariy productivity (NPP) has declined more than 6 percent globally over the last two decades, possibly as a result of climatic changes. NPP is the rate at which plant cells take in CO2 during photosynthesis from sunlight, using the carbon for growth. The NASA funded study appears in a recent issue of Geophysical Review Letters.

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In the high latitudes, rates of plankton growth declined by 7 percent in the North Atlantic basin, 9 percent in the North Pacific basin, and 10 percent in the Antarctic basin when comparing the 1980s dataset with the late 1990s observations."

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http://www.sciencedaily.com/releases/2003/09/030917072352.htm

A 10 percent NPP decline translates to millions of tons of atmospheric carbon dioxide per annum. In addition, unlike terrestrial plants, oceanic phytoplankton have considerable potential for long-term carbon mineralization and storage.

Over a year ago, in August 2002, declines of up to 30% were reported in northern oceans. Here's an archived link to the story:

http://archives.mundoacuatico.com/aug02/14augplummetingplankton.pdf

The paper modeled what would happen to upwelling if ocean circulation slowed due to global warming producing fresher warmer water and capping the downwelling zones near Greenland. The result was lower nutrient export from depths and therefore lower phytoplankton growth. A year or two ago a paper came out with evidence that ocean circulation had slowed. There are probably more factors than simply ocean circulation being affected by global warming in the decline in phytoplankton growth but it looks like that modeler may have been right.