Defining seasonal marine microbial community dynamics

TLDR

The study presents the longest high‑resolution 16S rRNA time‑series of marine microbes, sampling monthly for six years at a temperate coastal site off Plymouth, UK. Community richness was estimated from the 16S data, yielding 8,794 OTUs by single‑linkage preclustering and 21,130 OTUs after denoising. The community was dominated by Alphaproteobacteria, with seasonal dynamics driven mainly by environmental variables—especially day length, which explained over 65 % of diversity variance—while bacterial–bacterial correlations were stronger than those with eukaryotes or environmental factors.

Abstract

Abstract Here we describe, the longest microbial time-series analyzed to date using high-resolution 16S rRNA tag pyrosequencing of samples taken monthly over 6 years at a temperate marine coastal site off Plymouth, UK. Data treatment effected the estimation of community richness over a 6-year period, whereby 8794 operational taxonomic units (OTUs) were identified using single-linkage preclustering and 21 130 OTUs were identified by denoising the data. The Alphaproteobacteria were the most abundant Class, and the most frequently recorded OTUs were members of the Rickettsiales (SAR 11) and Rhodobacteriales. This near-surface ocean bacterial community showed strong repeatable seasonal patterns, which were defined by winter peaks in diversity across all years. Environmental variables explained far more variation in seasonally predictable bacteria than did data on protists or metazoan biomass. Change in day length alone explains >65% of the variance in community diversity. The results suggested that seasonal changes in environmental variables are more important than trophic interactions. Interestingly, microbial association network analysis showed that correlations in abundance were stronger within bacterial taxa rather than between bacteria and eukaryotes, or between bacteria and environmental variables.