Microbial communities in swamps of four mangrove reserves driven by interactions between physicochemical properties and microbe in the North Beibu Gulf, China

Mangroves are distributed in coastal and estuarine regions and are characterized as a sink for terrestrial pollution. It is believed that complex interactions between environmental factors and microbial communities exist in mangrove swamps. However, little is known about environment-microbe interactions. There is a need to clarify some important environmental factors shaping microbial communities and how environmental factors interact with microbial assemblages in mangrove swamps. In the present study, physicochemical and microbial characteristics in four mangrove reserves (named ZZW, Qin, Bei, and GQ) in the North Beibu Gulf were determined. The interactions between environmental factors and microbial assemblages were analyzed with statistical methods in addition to CCA and RDA. Higher concentrations of sulfate (SO42--S) and Fe but lower concentrations of total phosphorus (TP) and NO3--N were detected in ZZW and Qin. Nutrient elements (NO3--N, NH4+-N, organic matter (OM), SO42--S, Fe, and TP) were more important than heavy metals for determining the microbial assemblages, and NO3--N was the most important factor. NO3--N, SO42--S, TP, and Fe formed a significant co-occurrence network in conjunction with some bacterial taxa, most of which were Proteobacteria. Notably, comparatively elevated amounts of sulfate-reducing bacteria (Desulfatibacillum, Desulfomonile, and Desulfatiglans) and sulfur-oxidizing bacteria (Thioprofundum and Thiohalophilus) were found in ZZW and Qin. The co-occurrence network suggested that some bacteria involved in sulfate reduction and sulfur oxidation drive the transformation of P and N, resulting in the reduction of P and N in mangrove swamps. Through the additional utilization of multivariate regression tree (MRT) and co-occurrence network analysis, our research provides a new perspective for understanding the interactions between environmental factors and microbial communities in mangroves.

Automated summary

The interactions between environmental factors and microbial communities in mangroves were studied in this research. The results showed that nutrient elements played a more important role than heavy metals in determining the microbial assemblages. The co-occurrence network analysis revealed the involvement of sulfate-reducing and sulfur-oxidizing bacteria in the transformation of phosphorus and nitrogen.