Carbon from lush plankton blooms never reaches the deep ocean

May 7th, 2009 - 3:22 pm ICT by ANI  

Washington, May 7 (ANI): A new analysis has revealed that most of the carbon from lush plankton blooms, whether artificially fertilized or natural, never reaches the deep ocean.

The analysis was based on data collected by deep-diving Carbon Explorer that floats continuously, straight through the Antarctic winter.

The researchers who did the analysis were oceanographers Jim Bishop and Todd Wood of the US Department of Energy’s Lawrence Berkeley National Laboratory, who measured the fate of carbon particles originating in plankton blooms in the Southern Ocean.

Their study reveals that most of the carbon from lush plankton blooms never reaches the deep ocean.

The surprising discovery deals a blow to the simplest version of the Iron Hypothesis, whose adherents believe global warming can be slowed or even reversed by fertilizing plankton with iron in regions that are iron-poor, but rich in other nutrients like nitrogen, silicon, and phosphorus.

The Southern Ocean is one of the most important such regions.

“Just adding iron to the ocean hasn’t been demonstrated as a good plan for storing atmospheric carbon,” said Bishop, a member of Berkeley Lab’s Earth Sciences Division and a professor of Earth and planetary sciences at the University of California at Berkeley.

“What counts is the carbon that reaches the deep sea, and a lot of the carbon tied up in plankton blooms appears not to sink very fast or very far,” he added.

The reasons, while complex, are most likely due to the seasonal feeding behavior of planktonic animal life, and specifically to the effects of the dark Antarctic winter on plant and animal growth and the mixing of surface and deep waters by winter storms.

Phytoplankton blooms in the spring may indicate that much of the zooplankton (animal) population essential for carbon sedimentation has starved during the winter.

“We would never have made these surprising observations if the autonomous Carbon Explorer floats hadn’t been recording data 24 hours a day, seven days a week, at depths down to 800 meters or more, for over a year after the experiment’s original iron signature had disappeared,” Bishop said. (ANI)

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