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Images: A Drop in the Ocean is Teeming with Life

MIT/WHOI Joint Program student Jamie Becker sets up incubation experiments aboard the research vessel Melville during a research cruise to the South Pacific in the fall of 2010. Becker served as junior chief scientist on the BiG RAPA cruise, which was part of the C-MORE program (Center for Microbial Oceanography: Research and Education). During the cruise, researchers studied microbes along sharp biogeochemical gradients from the coast of Chile to Easter Island. The incubation experiments were designed to reveal how natural microbial communities respond to dissolved organic carbon from different sources.
(Photo by Mar Nieto-Cid, Woods Hole Oceanographic Institution)

Flasks contain samples to be injected into a liquid chromatograph-mass spectrometer to reveal the dissolved organic carbon in them. The brown fluid in the flask on the right contains organic carbon compounds produced and released by a specific autotroph. (The left flask is a control for the experiment, containing a seawater-based incubation medium with no autotrophs added.) Some  dissolved organic carbon compounds, like the brown pigments here, can be seen with the naked eye, but most are colorless and can’t be seen without the help of instruments such as a mass spectrometer.
(Photo by Jamie Becker, MIT WHOI Joint Program)

By closely examining the stew of organic carbon compounds dissolved in the ocean, scientists are beginning to reveal previously unknown relationships between specific marine microbes, forged by the materials they produce and consume. Autotrophic microbes convert carbon dioxide into organic carbon that heterotrophic microbes rely on for their survival. At one extreme (left), all autotrophs may produce a variety of compounds that a variety of heterotrophs consume. At the other extreme (right), specific autotrophs may produce specific compounds that specific heterotrophs consume. And there are many potential scenarios in between. These microscopic interactions are important cogs that mediate ocean food webs and influence the chemistry of our entire planet. (Illustration by Amy Caracappa-Qubeck, Woods Hole Oceanographic Institution)