Oral Presentation Freshwater Sciences 2023

Greenhouse Gas Emissions from Small Agricultural Ponds in Australia (#489)

Julian Sheppy 1 , Judith Rosentreter 1 , Bradley Eyre 1
  1. Centre for Coastal Biogeochemistry, Faculty of Science and Engineering, Southern Cross University, Lismore, NSW, Australia

Inland waters provide a substantial contribution to the global CO2, CH4, and N2O budgets. In particular, farm dams or man-made ponds in rural areas that store water for agricultural (cropping and livestock) purposes, have some of the highest greenhouse gas emissions per square meter among any freshwater ecosystem. Given the expansion of agriculture expected in the near future and subsequent increase in the cumulative surface area of farm dams, their contribution to greenhouse gas budgets will likely grow. Despite this, emissions from small man-made waterbodies, such as farm dams, are currently unaccounted for in global models because estimates of emissions are constrained by a lack of data on their spatial extent and a scarcity of direct flux measurements. Most attempts to quantify greenhouse gas emissions from farm dams have focused on daytime fluxes resulting in underestimates of total diel emissions. In this study, 24-hour floating chamber incubations were conducted to calculate light and dark greenhouse gas fluxes from >20 subtropical farm dams in the Northern Rivers region of Australia. CO2/CH4 loggers in conjunction with discrete samples were used to track changes in CO2, CH4, and N2O concentration within chamber headspaces allowing us to determine the rate and direction of greenhouse gas fluxes from each pond over a full day-night cycle. Our results provide insight into how nighttime fluxes from farm dams differ from daytime fluxes and improve our understanding of temporal variations in greenhouse gas emissions. This information will be valuable for estimating total greenhouse gas emissions from inland waters in Australia and quantifying their contribution to regional and global CO2, CH4, and N2O budgets.

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