Up to 15% of a potent greenhouse gas in the atmosphere comes from an unlikely source: the guts of tiny aquatic invertebrates. When these creatures feed off of bottom sediments and suspended food particles, they ingest bacteria. The bacteria usually use oxygen to help them break down and process their food, but when they are subjected to oxygen-poor conditions in the invertebrate’s belly, they turn to nitrate. The result: nitrous oxide–a greenhouse gas with 310 times the warming effect of CO2. The invertebrates need nitrate-rich waters to spur the process. However, so managing the two big nitrate polluters–fertilizer and sewage runoff–would help to decrease the creatures’ emissions, the researchers report online 2 March in Proceedings of the National Academy of Sciences. (Photo: Christian Lott (MPI Bremen/HYDRA))
