Homogeneous selection shapes free‐living and particle‐associated bacterial communities in subtropical coastal waters

Abstract

Aim In microbial biogeography, it is crucial to link spatial patterns with underlying drivers in natural ecosystems. Bacterial communities driving key biogeochemical processes in coastal zones, which are important interfaces between terrestrial and marine ecosystems, are affected by perturbations due to both natural and anthropogenic factors. However, the assembly of bacterioplankton communities, either free‐living (FL) or particle‐associated, in coastal ecosystems is still poorly understood. Location Coastal South China Sea influenced by the Pearl River (SCSPR). Methods In this study, we investigated FL, nanoparticle‐associated (NA) and microparticle‐associated (MA) bacterial communities in the SCSPR, using environmental DNA metabarcoding based on the V4 region of the 16S rRNA gene. We assessed the relative importance of ecological processes using null model analyses based on a two‐step framework. Results We found that the observed amplicon sequence variants (ASVs) increased from FL, NA to MA communities, and a remarkably pervasive core set of ASVs closely belonged to potential hydrocarbonoclastic bacteria with wide habitat niche breadths. Analyses of similarity tests revealed that FL, NA and MA communities differed significantly but weakly, based on unweighted (R = 0.27, p < .001) and weighted (R = 0.18, p < .001) dissimilarities. Fundamental regulation of bacterial communities via homogeneous selection was most prominent in FL (90%), followed by NA (86.8%) and MA (73.3%), whereas the relative importance of dispersal limitation was most pronounced in MA (13.2%), followed by NA (11.7%) and FL (8.6%). Main conclusions Bacterial communities in the SCSPR can be predominantly influenced by human activities, as indicated by the core ASVs closely related to hydrocarbonoclastic bacteria. Importantly, anthropogenic influences can temporally overwhelm the large environmental heterogeneities in coastal ecosystems. This study fills knowledge gaps in bacterial community assembly, which may facilitate future studies regarding anthropogenic influences on coastal ecosystems.

Free-living and particle-attached bacterial community composition, assembly processes and determinants across spatiotemporal scales in a macrotidal temperate estuary

“…Ecological null modeling showed that FL and PA bacterial community assemblies were largely driven by homogeneous selection, indicating that the biotic and abiotic environmental conditions led to bacterial communities that were more similar than what would be expected by random changes. Few studies have quantified assembly processes for FL and PA communities in coastal ecosystems; however, homogeneous selection was an important driver in other land–sea transition areas 60 – 62 . The predominance of deterministic processes has been suggested to lead to communities being well adapted to their environment, thus potentially having a stronger biogeochemical impact than communities assembled through stochastic processes 63 .…”

The responses of prokaryotic communities to the algal blooms from the Pearl River estuary

“…We also found that bacteria and viruses have more apparent correlations to the prokaryotic communities than other factors (Table S5, Fig. 2D), which means the interactions among biotic factors may have a more signi cant positive in uence on community structure than previously forecasted (Wu et al 2020).…”

“…Prokaryotic communities in natural water bodies were shaped mainly by the homogeneous selection, which was imposed by low environmental variability and supported by the shallow distance-decay in the coastal East China Sea (Wu et al 2020). The stochastic processes were dominant in the process of algae outbreak and gradually transformed into deterministic processes with the blooming succession in this region (Shao et al 2020;Zhang et al 2018).…”

Cell size is a key ecological trait associated with biogeographic patterns of microbial eukaryotes in coastal waters

“…The concentration of dissolved oxygen was determined by the Winkler titration method, and nutrients (including NO 2 , NO 3 , PO 4 and SiO 3 ), dissolved organic carbon, and total suspended matter were all measured using standard protocols, as described in previous studies (Dai et al, 2009;Han et al, 2012). More details of the environmental factors measured are also as described previously (Wu et al, 2021).…”