Effect of Rhizophora apiculata plantation for improving water quality, growth, and health of mud crab.

Abstract

A deteriorated water quality is closely associated with disease outbreaks in aquaculture, where microorganisms play indispensable roles in improving water quality and aquatic animals' health. Mangrove is known to be a natural water quality filter and microbiological buffer of pathogen and prebiotics. However, it is unclear how and to what extent Rhizophora apiculata plantation is of benefits to the gut microbiota and growth over mud crab (Scylla paramamosain) aging. To address these concerns, we explored the bacterial communities in mud crab gut and rearing water at 45, 114, and 132 days after incubation, roughly corresponding to juvenile, pre-adult, and adult stages of mud crab. Results showed that 1-year R. apiculata plantation slightly increased the body weight of mud crab and improved water quality to a certain extent. Both bacterioplankton and gut bacterial communities were highly temporal dynamic, while the two communities were significantly distinct (ANOSIM r = 0.90, P = 0.0001). Relative abundances of dominant taxa in water and gut significantly varied between the plantation and the control conditions over mud crab aging. R. apiculata plantation promoted the stability of gut microbiota, as evidenced by more diverse core species. Furthermore, R. apiculata plantation led to the dominance of Verrucomicrobiae species in water and probiotic Bacteroidetes and Lactobacillales taxa in gut. A structural equation model revealed that water variables directly constrained gut microbiota, which in turn affected the body weight of mud crab (r = 0.52, P < 0.001). In addition, functional pathways facilitating immunity and lipid metabolism significantly increased in mud crab gut under the plantation, while those involved in infectious diseases exhibited the opposing trend. These findings greatly expand our understanding of the R. apiculata plantation effects on water quality, gut microbiota, and growth feature of mud crab. Overall, R. apiculata plantation is beneficial for mud crab growth and health. KEY POINTS: • A short-term R. apiculata plantation could potentially improve water quality. • Bacterioplankton is more sensitive than mud crab gut microbiota in response to R. apiculata plantation. • R. apiculata plantation enhances mud crab resistance against pathogen invasion. • R. apiculata plantation alters mud crab gut microbiota, which in turn promotes their body weight.