Humans are pumping roughly 33 billion tonnes (36 billion tons) of carbon dioxide into the air each year. If all that showed up in the atmosphere, it would accelerate global warming even further. The ocean, however, absorbs around half of that CO2. Phytoplankton (essentially, microscopic plants) that live near the sea’s surface take in a lot of it as they photosynthesize, ultimately flushing the CO2 into the cold, dense depths, where it stays trapped for centuries.

How does it travel all those fathoms? Until now, scientists have chalked it up mainly to gravity—to the sinking of phytoplankton that have either died or been eaten and excreted by fish. But new research reveals that we have deep-sea fish to thank for transferring a lot of that carbon into the depths—and that sinking alone wouldn’t do the trick.

In fact, bottom-dwellers transfer more than a million tonnes of CO2 a year from surface waters of the UK and Ireland, helpfully storing between €8 million and €14 million ($10.9 million and $19 million) a year in carbon credit value, says a new study (paywall) by a University of Southampton team. Killing too many of those fishes, as well as the ones they feed on, risks damaging the ocean’s ability to store carbon, leaving more CO2 in the atmosphere.

We need to make more fish!!