Archaeal community in a human-disturbed watershed in southeast China: diversity, distribution, and responses to environmental changes

The response of freshwater bacterial community to anthropogenic disturbance has been well documented, yet the studies of freshwater archaeal community are rare, especially in lotic environments. Here, we investigated planktonic and benthic archaeal communities in a human-perturbed watershed (Jiulong River Watershed, JRW) of southeast China by using Illumina 16S ribosomal RNA gene amplicon sequencing. The results of taxonomic assignments indicated that SAGMGC-1, Methanobacteriaceae, Methanospirillaceae, and Methanoregulaceae were the four most abundant families in surface waters, accounting for 12.65, 23.21, 18.58 and 10.97 % of planktonic communities, whereas Nitrososphaeraceae and Miscellaneous Crenarchaeotic Group occupied more than 49 % of benthic communities. The compositions of archaeal communities and populations in waters and sediments were significantly different from each other. Remarkably, the detection frequencies of families Methanobacteriaceae and Methanospirillaceae, and genera Methanobrevibacter and Methanosphaera in planktonic communities correlated strongly with bacterial fecal indicator, suggesting some parts of methanogenic Archaea may come from fecal contamination. Because soluble reactive phosphorus (SRP) and the ratio of dissolved inorganic nitrogen to SRP instead of nitrogen nutrients showed significant correlation with several planktonic Nitrosopumilus- and Nitrosotalea-like OTUs, Thaumarchaeota may play an unexplored role in biogeochemical cycling of river phosphorus. Multivariate statistical analyses revealed that the variation of alpha-diversity of planktonic archaeal community was best explained by water temperature, whereas nutrient concentrations and stoichiometry were the significant drivers of beta-diversity of planktonic and benthic communities. Taken together, these results demonstrate that the structure of archaeal communities in the JRW is sensitive to anthropogenic disturbances caused by riparian human activities.