N2O in Surface Ocean

The goal of the project is to understand nitrous oxide (N2O) consumption in surface waters, by measuring rates of N2O consumption, determining what factors control the rates, and characterizing the microbes involved in the process. Nitrous oxide consumption in surface waters has the potential to reduce net emissions of N2O to the atmosphere, but because biological N2O consumption is considered to be an obligately anaerobic process, it is generally not considered in evaluating N2O flux from the surface ocean. We have detected the presence of microbes capable of N2O consumption, and have measured potential rates of N2O consumption, in fully oxygenated surface waters. In order to assess its potential importance on a global scale, we need to measure N2O consumption in regions where N2O production is low on an aerial basis, but large overall because those regions comprise 97% of the surface ocean. Ship time is requested for one expedition to the North Atlantic, a region where N2O is close to equilibrium with the atmosphere, and can be a weak net source or sink. The region in the North Atlantic is not directly connected to any strong oceanic N2O sources and thus represents the vast oxygenated surface ocean where the only known source of N2O is nitrification. The proposal describes a multi prong attack on the problem, including field work (see below) and molecular biological analysis of microbes and pathways associated with N2O consumption.