Conversion of earthen aquaculture ponds to integrated mangrove-aquaculture systems significantly reduced the emissions of CH4 and N2O

Abstract

Mangrove ecosystem helps mitigate regional and global climate change, but increasing land reclamation for aquaculture has degraded many mangroves wetlands. Integrated mangrove wetland-aquaculture systems can be a promising way to support both mangrove restoration and aquaculture, but its impacts on greenhouse gas emissions remain largely unknown. In this study, we compared CH₄ and N₂O fluxes between earthen aquaculture ponds (EAPs) and integrated mangrove-aquaculture systems (IMASs) in Beibu Gulf in southern China. Results showed that both EAPs and IMASs were CH₄ and N₂O emission sources with strong temporal variabilities. CH₄ fluxes were primarily affected by total organic carbon, dissolved oxygen and salinity. These fluxes were significantly larger in EAPs (976.3 ± 146.4µg m^-2h⁻¹) than in IMASs (60.3 ± 7.7µg m^-2h⁻¹). Ebullition was responsible for 52.9–93.4 % of the total CH₄ emission. The average N₂O flux in EAPs (3.4 ± 0.5µg m^-2h⁻¹) was 5.7 times higher than IMASs during the farming period and was mainly driven by nitrogenous substrate availability. The results highlight that integrated mangrove wetland-aquaculture systems can not only promote mangrove restoration and support aquaculture, but also mitigate greenhouse gases emissions from coastal wetlands.