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Cooperation and control in ocean microbial communities

Alan Flurry

The volume of the world’s oceans defines the gigantic scale on Earth – 300 million cubic miles, and an average depth of 12,000 feet. Of all the activity taking place there at every moment, any one part can be difficult to understand, making predictions difficult if not impossible. But scientists are starting to figure out some of its most complex processes.

The concentration of bacteria around phytoplankton, for example, and how these organisms associate and release compounds hold enormous consequences for carbon cycling in the oceans. New research from the University of Georgia describes the biological possibilities of successful actors in microbial communities and sets the stage for how half of all organic carbon in the oceans is processed.

The findings were published Feb. 3 in the Proceedings of the National Academy of Sciences.

Phytoplankton in the oceans use sunlight and carbon dioxide to make organic compounds. Bacterial communities in the oceans subsist on the organic compounds released by phytoplankton. This relationship results in close physical associations between phytoplankton and bacteria in seawater, and provides opportunities for the two groups to interact, each providing certain compounds that the other needs to live.

“We wanted to understand why these organisms associate and what controls the associations,” said Mary Ann Moran, Regents’ Professor in the Franklin College of Arts and Sciences department of marine sciences and lead author on the study. “The possibility that phytoplankton control the species of bacteria that survive in the microbial communities forming around them allowed us to understand who and what determines success in the communities.”


Image: Mary Ann Moran (center) at the Coastal Summer Semester Program on Sapelo Island (Photo by Dorothy Kozlowski/UGA)

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