Microbe cities' may solve a key ocean mystery

"When marine snow made of dead plankton's shells, fish poop, dust particles, and other debris descends to the ocean floor, it carries atmospheric carbon the plankton used to make their calcite shells. It's one of the ways the ocean stores carbon, helping to keep greenhouse gases from turning the planet into an oversize toaster oven. Yet scientists realized that something has been dissolving those calcite shells and releasing carbon dioxide, reducing the ocean's carbon-trapping capacity."

"The study published in the Proceedings of the National Academy of Sciences USA identified the culprit: dense microbe cities living inside the marine snow. The individual cities are microscopic, but collectively they have powerful effects on Earth's climate because the ocean is home to an inconceivable number of microbes. A shot glass full of seawater can contain millions of bacterial cells."

"If you were to take every bacterial cell in the ocean and string them end to end like a chain of pearls, it would stretch 50 times around the Milky Way, says study co-author Andrew Babbin, an oceanographer at the Massachusetts Institute of Technology. To study the microbial cities, we brought the ocean into the laboratory, says Benedict Borer, lead study author and a biogeochemist at Rutgers University."

"The scientists introduced microbes to a microfluidic chip designed to mimic marine-snow particles and added fluorescent molecules whose glow changed with oxygen levels and acidity. (The system was so sensitive that at first, people breathing in the lab were affecting measurements.)"

Marine snow made of dead plankton shells, fish feces, dust, and other debris transports atmospheric carbon to the ocean floor. Plankton calcify their shells using carbon, so sinking particles help store carbon in the ocean and limit greenhouse gas buildup. Scientists found that calcite shells are being dissolved, releasing carbon dioxide and weakening this carbon storage pathway. A study identified dense microbe communities inside marine snow as the cause. Individual microbial cities are microscopic, but the ocean contains vast numbers of microbes, giving them large climate impacts. Laboratory experiments used microfluidic chips that mimic marine-snow particles and fluorescent molecules that respond to oxygen and acidity, revealing how these conditions drive shell dissolution.

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