Sediment microbial community structure, enzymatic activities and functional gene abundance in the coastal hypersaline habitats

Abstract

Salt marsh vegetation, mud at and salt production are common features in worldwide coastal areas; however, their in uence on microbial community composition and structure has been poorly studied and rarely compared. In the present study, microbial community composition (phospholipid fatty acid (PLFA) pro ling and 16S rRNA gene sequencing (bacterial and archaeal)), enzymatic activities and abundance of functional genes in the sediments of salt ponds (crystallizer, condenser and reservoir), mud at and vegetated mud at were determined. Physicochemical characteristics of the sediments were also studied. Enzyme activities (β-glucosidase, urease and alkaline phosphatase) were considerably decreased in saltpan sediments because of elevated salinity while sediment of vegetated mud at showed the highest enzyme activities. Concentrations of total and microbial biomarker PLFAs (total bacterial, Gram-positive, Gram-negative, fungal and actinomycetes) were the highest in vegetated mud at sediments and the lowest in crystallizer sediments. Nonmetric-multidimensional scaling (NMS) analysis of PLFA data revealed that the microbial community of crystallizer, mud at and vegetated mud at was signi cantly different from each other as well as different from condenser and reservoir. The most predominant phyla within the classi ed bacterial fractions were Proteobacteria followed by Firmicutes, Bacteroidetes and Planctomycetes, while Euryarchaeota and Crenarchaeota phyla dominated the classi ed archaeal fraction. Cyanobacterial genotypes were the most dominant in the condenser. Mud at and vegetated mud at supported a greater abundance of Bacteroidetes and Actinobacteria, respectively. The results of the present study suggest that salt ponds had signi cantly decreased the microbial and enzyme activities in comparison to mud at and vegetated mud at sediments due to very high salinity, ionic concentrations and devoid of vegetation.