Response of prokaryotic communities to extreme precipitation events in an urban coastal lagoon: A case study of Yundang lagoon, China

Increasing extreme precipitation events (EPEs) can induce biogeochemical disturbances in the coastal lagoon ecosystems. Very little is known about the response of prokaryotic communities to such influences, which are the key components mediating the biogeochemical cycling in lagoons. Here 16S rRNA gene amplicon sequencing and high-through quantitative PCR (HT-qPCR) were employed to investigate the distribution of prokaryotic communities and fecal indicator genes in the surface waters of Yundang lagoon, Xiamen, China during EPEs, respectively. Prokaryotic communities from rainwaters, influents (IFs) and effluents (EFs) from a nearby wastewater treatment plant were also characterised. The results indicated a significant variation in the composition of lagoon prokaryotic communities compared with rainwaters, IFs and EFs. Multivariate and phylogenetic signal analyses revealed that environmental filtering, mainly controlled by salinity, was the major ecological process responsible for the temporal succession of lagoon prokaryotic communities during EPEs. Moreover, the pollution indicator taxa (based on amplicon sequencing) and fecal indicator genes (based on HT-qPCR) demonstrated that EPEs may induce sewage overflows and fecal pollution (mainly from humans and dogs), resulting in an increase in the relative abundance of pollution indicator taxa and genes in Yundang lagoon. Network analysis illustrated that the number of network edges and keystone species decreased along the sampling times, implying that EPEs-induced disturbances may affect prokaryotic species associations. Taken together, this study provides an enhanced understanding of the responses of lagoon prokaryotic communities to EPEs-induced disturbances.