N2O in the nBUS - Cruise 2 of 2

Amendment to the original description: Unforeseen challenges occurred when sampling in the northern Benguela Upwelling System (nBUS). We were unable to obtain samples for NSF projects 2342607 and 2342606, therefore we will sample in the northern Gulf of Mexico for cruise 2 of 2, which is funded by the original NSF award 2113936, and referred to as N20 in the nBUS. This second cruise in the northern Gulf of Mexico (nGOM), provides an opportunity to sample sediments underlying a hypoxic water mass. Using multi-isotope and microbial ecology approaches we will use these samples to investigate sedimentary nitrous oxide production and consumption in the nGOM. Concentration, stable isotopic and isotopomer data, 15N-labeled rate measurements as well as molecular ecology data will be generated and synthesized to determine 1) the net sediment-water column flux of N2O, 2) N2O production and consumption rates for different processes, 3) controls by environmental conditions (e.g., oxygen (O2), hydrogen sulfide (H2S), and nutrient concentrations, O2 penetration depth, as well as organic matter elemental composition), and 4) the link between measured rates and the active processes that lead to N2O production by bacteria, archaea, and microbial eukaryotes, as well as bacterial and archaeal N2O consumption.