Bioturbation by the razor clam (Sinonovacula constricta) on the microbial community and enzymatic activities in the sediment of an ecological aquaculture wastewater treatment system

Bioturbation by the razor clam, Sinonovacula constricta, influenced the redox conditions and changed the sedimentary environment, providing a suitable micro-environment for microbial growth. However, the mechanism of the integrated razor clam-microbial community in organic matter mineralization remains elusive. To study this mechanism, an in situ experiment was conducted to investigate the bioturbation effects of S. constricta on the microbial community and enzymeactivities in the sediment of an ecological aquaculture wastewater treatment system. According to principal coordinate analysis (PCoA) and PERMANOVA, we found that the microbial community was significantly (P < 0.05) influenced by the bioturbation effect of S. constricta. Linear discriminant analysis effect size (LEfSe) showed that species involved in reduced effluent concentrations of TN and TP, such as Prolixibacteraceae, Nitrospira and Actinobacteria, were increased significantly (P < 0.05) by S. constricta. Molecular ecological network (MENs) analysis indicated that the bioturbation effect of S. constricta increased the complexity of interspecies interaction and changed the topological properties of individual OTUs. The results elucidated that S. constricta increased the microbial community network, as substantiated by a higher total number of nodes and a shorter geodesic distance. Zi < 2.5 and Pi < 0.62 inMENs showed that the S. constricta treatment significantly increased (P < 0.05) the potential microbial community, with the keystone (OTU747049) Proteobacteria and (OTU74388) Bacteroidetes family Prolixibacteraceae, which connected different co-expressed OTUs. Furthermore, S. constricta significantly increased (P < 0.05) the enzymatic activities (alkaline phosphatase (APA),dehydrogenase and urease) of the substrate at different sampling depths. Overall, this study provides evidence that the bioturbation effect of S. constricta changes the microbial community structure, increases enzymatic activities and accelerates the degradation of organic matter in an aquaculture wastewater environment. (C) 2018 Published by Elsevier B.V.