Sixteen panels of four different clumps of marine microorganisms collected from a methane seep off the coast of northern California. Each clump, called an aggregate, is about 10 microns (millionths of a meter) across. The microbes have been tagged with fluorescent markers. DNA glows blue.
Off the western coast of Costa Rica, where the crust of the North American continent ends, the underwater terrain is smooth and barren. A thousand meters deep, the seafloor is beyond the reach of the sun and low in oxygen. “It’s just amazing—the bottom of the deep ocean at that site is surprisingly desolate,” says Anne Dekas, a graduate stu dent in Assistant Professor of Geobiology Victoria Orphan’s lab. “It’s just flat and gray sediment for as long as you can see.” Break ing the monotony are occasional methane seeps—places where methane trapped in ice (see box) is released and bubbles out through cracks in the seabed—and at these seeps, Dekas says, “it’s completely differ ent. It’s an oasis of life.” Boasting clams, crabs, tube worms, shrimp, and microbial mats, these dark, deep-sea oases are made possible by microorganisms that eat the bountiful methane, producing nutrients and sources of energy for the rest of the food chain.
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