We need the ocean to trap carbon.
Plankton pull atmospheric CO2, turn it into calcite shells, and eventually die. Their bodies sink. This “marine snow”—a slurry of shells, fish waste, and dust—carries that carbon toward the deep. It is a critical filter, keeping greenhouse gases from turning our planet into a broiler oven.
Or it was.
Something is chewing through those shells before they hit the floor. It dissolves the calcite and releases carbon dioxide right back into the water. We lost that storage potential.
A study in Proceedings of the National Academy of Sciences finally named the culprit: microscopic cities. Dense colonies of bacteria living inside the falling snow itself.
A galaxy of germs
One cell doesn’t matter. The population does.
There are so many microbes in the ocean that the number defies normal comprehension. Andrew Babbin, an MIT oceanographer, put it into perspective. If you strung every bacterial cell in the sea together? The chain would wrap around the Milky Way 50 times.
Yes. Fifty times.
“If you were to take every microbial city… and string them end to end, it would stretch around our galaxy dozens of times over.”
Building the snow
Benedict Borer from Rutgers led the effort. He couldn’t just watch from a boat. The action was happening inside single particles. Too small to see.
So he brought the ocean to his desk.
Using microfluidic chips designed to mimic snowflakes, he added glowing molecules that reacted to oxygen and pH levels. The setup was sensitive. Painfully so. Early tests showed that researchers just breathing near the chip skewed the data.
“We had to account for the exhalation of the scientists in the room.”
They found the secret. The microbes weren’t just sitting there. They were breathing. Hard.
In tight quarters, these oxygen-guzzling bacteria consumed carbon and pumped out CO2. In seawater, that becomes carbonic acid. Acid eats calcium.
The result? Hot pockets of acidity dissolved the very shells that were supposed to carry carbon down.
Slower sink, faster escape
Here is the problem.
As the shells dissolve, the particles lose weight. Light things don’t sink fast.
The snow slows down. It lingers. And while it lingers, that carbon has time to leak back into the surface water instead of getting buried in the abyss. We wanted long-term storage. Instead, we’re getting a leaky bucket.
Hongjie Wang from the University of Rhode Island called it what it is: small-scale interactions driving large-scale chaos. Babbin called it terraforming.
Who are we to argue?
The microbes are rewriting the chemical rules of our planet. We are just starting to calculate the full acid balance, because the dissolving rock does fight back a little. But the clock is ticking on those sinking flakes.
Do we understand what they are really building down there?
Not quite yet. But they are certainly working.
