Microbial communities across nearshore to offshore coastal transects are primarily shaped by distance and temperature

Abstract

Summary Recent studies have focused on linking marine microbial communities with environmental factors, yet, relatively little is known about the drivers of microbial community patterns across the complex gradients from the nearshore to open ocean. Here, we examine microbial dynamics in 15 five‐station transects beginning at the estuarine Piver's Island Coastal Observatory (PICO) time‐series site and continuing 87 km across the continental shelf to the oligotrophic waters of the Sargasso Sea. 16S rRNA gene libraries reveal strong clustering by sampling site with distinct nearshore, continental shelf and offshore oceanic communities. Water temperature and distance from shore (which serves as a proxy for gradients in factors such as productivity, terrestrial input and nutrients) both most influence community composition. However, at the phylotype level, modelling shows the distribution of some taxa is linked to temperature, others to distance from shore and some by both factors, highlighting that taxa with distinct environmental preferences underlie apparent clustering by station. Thus, continental margins contain microbial communities that are distinct from those of either the nearshore or the offshore environments and contain mixtures of phylotypes with nearshore or offshore preferences rather than those unique to the shelf environment.

Seasonality in Spatial Turnover of Bacterioplankton Along an Ecological Gradient in the East China Sea: Biogeographic Patterns, Processes and Drivers

“…We found that seasonality overwhelmed spatial variability of bacterial community composition. In contrast, at the similar spatial scale, the spatial variability dominated patterns were found across a river-to-ocean gradient in the Columbia River margin [ 14 ] and along a nearshore-to-offshore gradient in the Sargasso Sea [ 10 ], corresponding to the stronger environmental gradients over space (salinity in the former and water temperature in the latter) compared with those in this work. Here, the strong seasonal succession in bacterioplankton could be due to the strong seasonal changes in water temperature and DO concentration.…”

“…In this study, we tested two biogeographic patterns: (i) covariation of community composition and distance to shore (land) (Pattern I) and (ii) distance–decay relationship (Pattern II). Wang et al found significant Pattern I in the Sargasso Sea by integrating data from many different months for years [ 10 ], but the existence of seasonality was not concerned. In our work, seasonal consistency in Pattern I was evidenced by significant correlation between DTL and PCoA 1 and 2 coordinates in the summer, autumn, and winter, but the spatial turnover of bacterial communities in the spring did not fit Pattern I.…”

“…Seasonal succession in bacterioplankton community composition is commonly driven by seasonal changes in environmental conditions such as water temperature, nutrients, and phytoplankton (as reviewed in [ 9 ]). On the other hand, seasonal variability of environmental conditions may depend on geographic factors such as latitude and distance to shore of the sampling stations [ 10 , 11 ]. With the change of latitude or distance to shore, multiple environmental gradients could be formed in coastal waters, thus leading to spatial turnover of bacterial communities [ 12 , 13 ].…”

“…With the change of latitude or distance to shore, multiple environmental gradients could be formed in coastal waters, thus leading to spatial turnover of bacterial communities [ 12 , 13 ]. Some previous studies have considered the coastal areas with ecological gradients as ideal models for understanding the interplay of seasonal and spatial variability in bacterioplankton communities [ 10 , 14 ]. However, the seasonality in biogeographic patterns and underlying processes of bacterioplankton along coastal environmental gradients is largely unknown.…”

“…With an increase in spatial scale and/or environmental gradient strength, the larger changes of environmental conditions over space and/or enhanced dispersal limitation due to the longer geographic distance lead to a pattern where spatial variability overwhelms seasonality [ 14 ]. Spatial variability of bacterial communities in coastal waters can be simultaneously constrained by abiotic factors, including salinity [ 16 , 17 ], water temperature [ 7 , 18 ], suspended particles [ 13 ] and nutrients [ 7 , 19 ], and spatial factors [ 10 , 11 ] in various oceanic provinces. Biotic factors like phytoplankton biomass and composition can also be crucial drivers [ 20 , 21 ].…”