Influence of environmental variables on methane related microbial activities in a tropical bio-secured zero-exchange shrimp culture system

Abstract

Recently, aquaculture has emerged as the fastest growing food-producing sector accounting for nearly 50% of the world's food fish and is an activity of economic importance worldwide. Aquaculture systems are considered as one of the potential contributors to atmospheric methane (CH4)-the second most important greenhouse gas (GHG). The present study was undertaken to assess the influence of environmental variables on the abundance of culturable methanotrophs (MOB), methane oxidation activity (MOA) and methane production activity (MPA) during a grow-out cycle in zero-exchange shrimp pond growing whiteleg shrimp, Litopenaeus vannamei. During the 96 days of culture (DoC), the abundance of MOB in the pond water and sediment, ranged between 3.04 x 103-1.8 x 104 CFU mL-1 and 3.36 x 105-3.17 x 106 CFU g-1, respectively. The mean potential rates of MOA and MPA in pond sediments were 392.71 ± 53.06 µmole g-1d-1 and 0.60 ± 0.30 µmole g-1d-1, respectively. The abundance of MOB and methane related activities were strongly influenced by the dissolved nitrogen species and total organic carbon (p < 0.05). In addition to providing the baseline data on microbial mediated methane activities, the study highlights the importance of methane oxidation/production processes in commercial earthen shrimp aquaculture system and the influence of environmental variables in regulating these processes. The results of this study would aid in developing environmental friendly management processes to reduce the efflux of GHG methane from shrimp aquaculture systems which is a thriving industry in the food sector.