A preliminary field-based assessment of greenhouse gas emissions from prawn aquaculture ponds in Bangladesh: effects of farm management and water quality

Abstract

Greenhouse gas (GHG) emissions from coastal aquaculture are an emerging environmental concern, with implications for ecosystem sustainability and climate mitigation. In this preliminary field-based study, we quantified carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous dioxide (N 2 O) fluxes from 35 randomly selected prawn farms in coastal Bangladesh, at a single time point using the floating chamber method, with concurrent water quality monitoring and farm management surveys, to identify key factors influencing in-pond GHG emissions. Extensive farming systems showed a higher CO 2 emission rate (1261.3 ± 727.0 g/ha/day) than semi-intensive farms, while CH 4 (10.3 ± 5.60 g/ha/day) and N 2 O (0.71 ± 0.53 g/ha/day) fluxes were higher in the semi-intensive farms. The total GHG emissions (CO₂ equivalent; CO₂e in a 100-year life span) were lowest in semi-intensive farms (898.3 ± 245.7 g/ha/day). Correlation analysis revealed significant negative associations between total CO 2 e emissions and salinity, feeding frequency, and carp stocking density, while standing crop showed a positive association. Random forest modelling further revealed that pond biomass, salinity, and feeding rate were important predictors of CO 2 , whereas CH 4 and N 2 O were primarily determined by water age and water source, respectively. Although this preliminary study was limited by the number of sampled farms and the temporal resolution of sampling, it cautiously proposes frequent water exchange, stocking-density optimization, carp integration, increased feeding frequency, and enhanced farmers’ knowledge as possible options to reduce emissions but warrants further longitudinal investigation.

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