Effect of Bellamya purificata on organic matter degradation in surface sediment as revealed by amino acids

The accumulation of organic matter (OM) in the sediment of aquaculture ponds is a potential threat for aquaculture ecosystems and the surrounding environment. The snail Bellamya purificata is a potential bioremediation species which may solve this problem. To investigate the effects of B. purificata on OM degradation in surface sediment, an 84 d experiment was carried out. The experimental setup entailed 6 glass tanks which were divided into B. purificata treatment (BPT) and control (CON). At the end of the experiment, a significantly lower degradation index (DI), reactivity index (RI), and carbon-normalized yield of amino acids were observed in BPT compared to CON, with mean ± SD values of -0.47 ± 0.43, 1.24 ± 0.01, and 6.24 ± 0.44, respectively. BPT showed higher oxidation-reduction potential and bacterial 16S rRNA gene copies than CON. Total organic carbon, total nitrogen, and total hydrolysable amino acid concentrations in the BPT treatment were 1.83 ± 0.10%, 0.07 ± 0.01%, and 22.38 ± 0.53 µmol g -1 , respectively, all of which were significantly lower than in CON. A clustered heat-map of different indexes related to OM degradation in sediments showed the final BPT as one separate category, which was different from the initial samples and the final CON. Overall, B. purificata could effectively facilitate OM degradation by promoting oxidation-reduction potential and bacterial populations, and ultimately by inhibiting the OM accumulation in sediment. Our results therefore provide support for the application of B. purificata to reduce the risk of endogenous pollution caused by OM accumulation in aquaculture ponds.