Apparently, bacteria aren’t the only microorganisms in the sea that pump large quantities of certain greenhouse gases into the atmosphere. A new study shows that marine archaea – a distinct group of single-celled microorganisms – might be the primary source of nitrous oxide emissions from the world’s oceans. These marine archaea differ from bacteria in that they contain several genes and metabolic pathways that are more closely related to eukaryotic organisms. Alyson Santoro and colleagues grew cultures of archaea from the Pacific Ocean in the laboratory and found that the microorganisms produce significant amounts of heat-trapping nitrous oxide through the oxidization of ammonia. Isotopic measurements show that these marine archaea produce more nitrous oxide than marine bacteria, suggesting that they could be largely responsible for the large amounts of the greenhouse gas moving from the oceans to the atmosphere.