A comparative investigation of the biodiversity, assembly, and interaction of epiphytic and epipelic biofilms in shallow lakes from four geographical zones

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Epiphytic and epipelic biofilms are two types of microbial assemblages growing on biotic and abiotic substrates, respectively, in shallow lakes. Nevertheless, little is understood about the factors governing the microbial community assembly and interaction of biofilms in shallow lakes located in different geographical zones. This study explored the differences in microbial community in biofilms on Ceratophylum demersum leaves and surface sediments in Lake Ulansu (China), Silkeborg Langsø (Denmark), Gaharwa (Rwanda), and Weija (Ghana). The results show that nutrients and environmental parameters differed significantly in overlying water among four lakes. The highest conductivity (2538.87 μS/cm) was detected in overlying water in Ulansu, and there were higher nutrient concentrations in two African lakes than Lake Ulansu and Langsø. Significant differences in bacterial and micro-eukaryotic α-diversity were detected between epipelic and epiphytic biofilms in each lake. Only 43 and 25 bacterial OTUs (6 and 1 micro-eukaryotic OTUs) were shared by epiphytic and epipelic biofilms in four lakes, respectively. The most dominant bacterial phyla were Actinobacteria, Proteobacteria, Firmicutes, and Planctomycetes. For micro-eukaryotes SAR, Phragmoplastophyta, Rotifera, and Ascomycota were dominant in all four lakes. The neutral and null models reveal that deterministic processes significantly influence microbial communities in epipelic and epiphytic biofilms of four global lakes. EC, pH, temperature, and nitrogen compounds were the main driving factors for microbial communities in these lakes. The examination of co-occurrence networks revealed that microbial interactions in epipelic biofilms were more stable and complicated than those in epiphytic biofilms. Overall, the findings provide new and additional insights to better understand the influence and role of epiphytic and epipelic biofilms and environmental parameters on bacterial and micro-eukaryotic biodiversity, interactions, assemblages, and ecological functions in global shallow lakes.