Methane production in aerobic oligotrophic surface water in the central Arctic Ocean

[摘要] A methane surplus relative to the atmospheric equilibrium is a frequentlyobserved feature of ocean surface water. Despite the common fact thatbiological processes are responsible for its origin, the formation ofmethane in aerobic surface water is still poorly understood. We report onmethane production in the central Arctic Ocean, which was exclusivelydetected in Pacific derived water but not nearby in Atlantic derived water.The two water masses are distinguished by their different nitrate tophosphate ratios. We show that methane production occurs if nitrate isdepleted but phosphate is available as a P source. Apparently the low N:Pratio enhances the ability of bacteria to compete for phosphate while thephytoplankton metabolite dimethylsulfoniopropionate (DMSP) is utilized as aC source. This was verified by experimentally induced methane production inDMSP spiked Arctic sea water. Accordingly we propose that methylatedcompounds may serve as precursors for methane and thermodynamic calculationsshow that methylotrophic methanogenesis can provide energy in aerobicenvironments.

[学科分类] 地球化学与岩石