The oceans emit an estimated 30% of the nitrous oxide (N2O) entering the atmosphere. Nitrous oxide gives rise to NO (nitric oxide) when it reacts with oxygen atoms, and this NO in turn reacts with ozone. As a result, N2O is the main naturally occurring "regulator" of stratopheric ozone. N2O is also a potent GHG; it has 310-times the heat-trapping potential of CO2. [In soil, N2O is produced during the microbial processes of nitrification and denitrification.]
Yet the oceanic source of N2O has puzzled researchers for years. Bacteria, long the leading candidate, can generate N2O, but the seas do not appear (it is believed) to contain enough bacteria to account for all of the N2O that the marine world has been producing. Now researchers offer an alternative view, archaea (see http://en.wikipedia.org/wiki/Archaea), which were once thought to be a type of bacteria. Despite their vast numbers, the presence of marine archaea only came to light in 1992.
Researchers have found that archaea transform ammonia into N2O (at least in the lab). Since there is no shortage of ammonia in the oceans, the researchers believe that they have found a likely key to the "mystery."
The study can be found at http://www.sciencemag.org/content/early/2011/07/27/science.1208239.abstract.