Spatial and temporal variability of methane emissions and environmental conditions in a hyper-eutrophic fishpond

Abstract. Estimations of methane (CH4) emissions are often based on point measurements using either flux chambers or a transfer coefficient method, which may lead to strong underestimation of the total CH4 fluxes. In order to demonstrate more precise measurements of the CH4 fluxes from an aquaculture pond, using a higher resolution sampling approach we examined the spatiotemporal variability of CH4 concentrations in the water, related fluxes (diffusive and ebullitive) and relevant environmental conditions (temperature, oxygen, chlorophyll a) during three diurnal campaigns in a hyper-eutrophic fishpond. Our data show remarkable variance spanning several orders of magnitude while diffusive fluxes accounted for only a minor fraction of total CH4 fluxes (4.1 %–18.5 %). Linear mixed-effects models identified water depth as the only significant predictor of CH4 fluxes. Our findings necessitate complex sampling strategies involving temporal and spatial variability for reliable estimates of the role of fishponds in a global methane budget.