Warming Oceans Put Kink in Food Chain, Study Says

January 30, 2007

The growth of tiny plants at the base of the ocean food chain is tightly linked to changes in the climate, according to a recent study.

The finding shows that as temperatures warm, the growth of single-celled ocean plants called phytoplankton slows at Earth's mid and low latitudes. The plants' growth increases when the climate cools.

While the findings are related to short-term changes in climate, they help scientists predict how the ocean will respond to long-term climate change, according to Jorge Sarmiento, an atmospheric and ocean scientist at Princeton University in New Jersey.

"This is telling us we can expect reduced biological production [the ability to support life such as plants, fish, and wildlife] with global warming in many regions of the world," he said.

Sarmiento is a co-author of the study, which was published last month in the science journal Nature.

Michael Behrenfeld, a botanist at Oregon State University in Corvallis, was lead author of the study. He said the research demonstrates a solid link between climate change and marine life.

The growth of phytoplankton, for example, influences how much food fish have to eat, which in turn affects the marine birds that eat the fish.

As the Earth warms, Behrenfeld said, changes in the upper ocean will change not only phytoplankton but also the species that dominate different regions of the environment.

"It will change the structure of the ecosystem," he said.

Shifting Growth

Behrenfeld's team calculated the growth rates of the tiny ocean plants using satellite data collected between 1997 and 2006. The growth rates were then correlated with records of Earth's climate during that time.

The satellite imagery detected shifts in the color of the ocean from blue to green. The color shifts reflect changes in the amount of phytoplankton in the water.

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