Distribution and fluxes of trimethylamine in the Northwest Pacific marginal seas

Abstract

Trimethylamine (TMA) is one of the dominant volatile amines that can impact atmospheric nucleation and serve as important carbon and nitrogen sources for microbes in marine environments. Despite the significance of this climate relevant gas, the distribution, fluxes and controls of TMA remain largely unconstrained in the ocean. Here we reported the abundance of TMA in the water column, sediment and atmosphere of Northwest Pacific marginal seas, and illustrated the distribution, source and exchange fluxes across the sea-air and sediment-water interfaces. TMA in surface waters ranged from 0.3 nM to 10.1 nM (2.5 ± 2.6 nM) and decreased from inshore to offshore waters. Significant relationships were observed between TMA and chlorophyll a, suggesting the biological control of TMA production from phytoplankton. The average sea-to-air flux of TMA in the Yellow Sea and East China Sea was 0.12 μmol m⁻² d⁻¹, contributing to an annual emission of 0.7 Gg N TMA to the atmosphere, which suggested a significant relative contribution of continental shelf seas to global oceanic TMA emissions. In marine sediments, dissolved TMA in the porewater was low (2.5–22.4 nM), while the exchangeable and base-extractable pools of TMA from the solid phase were much more abundant (> 200 nmol kg⁻¹). Surface sediment was a source of TMA in the overlying waters, and the estimated sediment-water flux was 3.5 nmol m⁻² d⁻¹. Collectively, these results shed light on the sources and sinks of TMA across the air-sea and sediment-water interfaces and highlighted the importance of coastal waters as a significant source of TMA to the atmosphere.