Ideas and perspectives: A strategic assessment of methane and nitrous oxide measurements in the marine environment

Abstract

Abstract. In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics – namely production, consumption and net emissions – is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for a number of climate-active trace gases including methane (CH4) and nitrous oxide (N2O). The temporal and spatial distributions of CH4 and N2O are controlled by the interaction of complex biogeochemical and physical processes. To evaluate and quantify the importance of these mechanisms relevant to marine CH4 and N2O cycling requires a combination of traditional scientific disciplines including oceanography, microbiology, and numerical modeling. Fundamental to all of these efforts is ensuring that the datasets produced by independent scientists around the world are comparable and interoperable. Equally critical is transparent communication within the research community about the technical improvements required to increase our collective understanding of marine CH4 and N2O. An Ocean Carbon & Biogeochemistry (OCB) sponsored workshop was organized to enhance dialogue and collaborations pertaining to marine CH4 and N2O. Here, we summarize the outcomes from the workshop to describe the challenges and opportunities for near-future CH4 and N2O research in the marine environment.

Spatial Distribution of CO2, CH4, and N2O in the Great Barrier Reef Revealed Through High Resolution Sampling and Isotopic Analysis

“…inputs from river and groundwater discharge, can lead to large variability in continental shelf GHG dynamics that can differ from open ocean source/sink trends (Bange, 2006). Further compounding continental shelf GHG dynamics uncertainty is a paucity of measurements in coastal areas (Wilson et al, 2020).…”

“…With high oxygen saturation, sulfate availability and mostly oligotrophic seawater, lagoons should be unconducive for production of CH 4 (via methanogenesis) (Saunois et al, 2020). However, CH 4 supersaturation is common throughout aerobic oceanic surface waters in part due to microbial respiration of dimethylsulfoniopropionate (DMSP) and other phosphorus and sulfur containing compounds (Karl et al, 2008;Wilson et al, 2020). Coral reefs are hotspots for DMSP production (Broadbent et al, 2002;Deschaseaux et al, 2019), which may enhance CH 4 production by stimulating microbial respiration (Damm et al, 2009;Frade et al, 2016;Karl et al, 2008).…”