AUTHOR=Vroom Renske J. E. , Kosten Sarian , Almeida Rafael M. , Mendonça Raquel , Muzitano Ive S. , Barbosa Icaro , Nasário Jonas , Oliveira Junior Ernandes S. , Flecker Alexander S. , Barros Nathan TITLE=Widespread dominance of methane ebullition over diffusion in freshwater aquaculture ponds JOURNAL=Frontiers in Water VOLUME=5 YEAR=2023 URL=https://www.frontiersin.org/journals/water/articles/10.3389/frwa.2023.1256799 DOI=10.3389/frwa.2023.1256799 ISSN=2624-9375 ABSTRACT=

An ever-increasing demand for protein-rich food sources combined with dwindling wild fish stocks has caused the aquaculture sector to boom in the last two decades. Although fishponds are potentially strong emitters of the greenhouse gas methane (CH₄), little is known about the magnitude, pathways, and drivers of these emissions. We measured diffusive CH₄ emissions at the margin and in the center of 52 freshwater fishponds in Brazil. In a subset of ponds (n = 31) we additionally quantified ebullitive CH₄ fluxes and sampled water and sediment for biogeochemical analyses. Sediments (n = 20) were incubated to quantify potential CH₄ production. Ebullitive CH₄ emissions ranged between 0 and 477 mg m⁻² d⁻¹ and contributed substantially (median 85%) to total CH₄ emissions, surpassing diffusive emissions in 81% of ponds. Diffusive CH₄ emissions were higher in the center (median 11.4 mg CH₄ m⁻² d⁻¹) than at the margin (median 6.1 mg CH₄ m⁻² d⁻¹) in 90% of ponds. Sediment CH₄ production ranged between 0 and 3.17 mg CH₄ g C⁻¹ d⁻¹. We found no relation between sediment CH₄ production and in situ emissions. Our findings suggest that dominance of CH₄ ebullition over diffusion is widespread across aquaculture ponds. Management practices to minimize the carbon footprint of aquaculture production should focus on reducing sediment accumulation and CH₄ ebullition.