Tidally Induced Spatial Heterogeneity of Greenhouse Gas Fluxes in an Estuary.

Estuaries naturally contribute greenhouse gas fluxes to the environment through biogeochemical processes that are heterogeneous in both space and time. Therefore, it is important to understand the driving forces behind greenhouse gas production, consumption, and overall flux to understand how it might change with the advent of environmental stressors. Water table depth and ensuing redox processes are the main drivers behind anaerobic respiration; in an estuary, the water table is influenced by the proximity to tidal channels. Here, we aim to identify the relationship between the water table fluctuations, sediment biogeochemistry, and greenhouse gas flux within a tidally influenced estuary.  High-resolution water table and gas flux data was correlated to biogeochemical trends in a site near a tidal channel, and an interior site further away from a tidal channel. We found that the near channel site had a more tidally dependent water table with consequent fluctuations in redox profiles, which contributed to the variability in greenhouse gas flux, whereas the interior site had a more seasonal water table and greenhouse gas trend.  These results will be discussed in the context of scaling up site heterogeneity for more robust climate modelling.