Bacteria‐driven production of alkyl nitrates in seawater

Abstract

AbstractAircraft‐ and ship‐borne measurements have shown that the ocean is a large, diffuse source for short chain (C1–C3) gas phase alkyl nitrates (RONO2). Photochemical production of RONO2 has been demonstrated previously as a viable mechanism in surface waters; however, it cannot account for the observed depth profile of RONO2, suggesting an additional, dark RONO2 production mechanism. We present measurements of gas phase C1–C5 alkyl nitrates emitted from seawater in a controlled mesocosm experiment conducted under low‐light conditions in a glass‐walled wave channel. Ethyl and butyl nitrate emission rates from seawater are strongly correlated with the abundance of heterotrophic bacteria (R2 ≥ 0.89) and show no correlation to chlorophyll a concentration. Controlled flask experiments conducted using ambient and sterile seawater, inoculated with a heterotrophic bacterium, confirm that bacterial driven production of select RONO2 can proceed efficiently in the absence of light.