CULTIVATION EFFORTS AND SIZE FRACTIONATED RATES SUPPORT POTENTIAL SURFACE WATER NITROUS OXIDE CYCLE

Nitrous oxide (N₂O) is a potent greenhouse gas that is predicted to be the single greatest ozone depleting agent of the 21^st century. Despite making up only 3% of the surface ocean, oxygen minimum zones (OMZs) are responsible for as much as 15-21% of global N₂O emissions, predominately from denitrification. The only known biological sink for N₂O is the last step of the denitrification pathway, mediated by an enzyme that is thought to be oxygen intolerant. Therefore, N₂O respiration should not be favored in surface-living microbes. Previous work in the Eastern Tropical North Pacific OMZ, however, provided evidence for significant potential rates of surface water N₂O consumption, and implied a potential role for particles to serve as anoxic microsites. We tested this hypothesis by enriching for surface water N₂O reducers from the Eastern Tropical South Pacific (ETSP) OMZ targeting several size fractions and different organic substrates. Having obtained a few dozen N₂O-respiring isolates from surface water, we then characterize them in terms of their phylogeny, their capabilities for nitrous oxide consumption, and other anaerobic respiratory reactions. Additionally, we report simulated in-situ and potential N₂O production and consumption rates in surface water from varying size fractions and oxygen concentrations. These rates imply a potential cryptic N₂O cycle in surface water that is distributed across the particle size spectrum.

Presentation Preference: Poster

Primary Presenter: Jessica Hexter, Princeton University (jh6959@princeton.edu)

Authors:

Jessica Hexter, Princeton University  (jh6959@princeton.edu)

Xianhui Wan, Princeton University, Xiamen University  (xianhuiw@princeton.edu)

Hui Shen, Princeton University, Xiamen University  (hs6419@princeton.edu)

Moriah Kunes, Princeton University  (mkunes@princeton.edu)

Bess Ward, Princeton University  (bbw@princeton.edu)