Heterogeneous selection dominated the temporal variation of the planktonic prokaryotic community during different seasons in the coastal waters of Bohai Bay

To explore temporal and spatial effects on the planktonic prokaryotic community composition (PCC) in the coastal region of the Bohai Sea, surface water samples were collected from 12 to 28 regularly distributed sites in Bohai Bay across 3 months from different seasons to characterize the PCC using high-throughput sequencing of the 16S rRNA V4 region. Prokaryotic α- and β-diversity showed significant temporal variation during the three sampling months. VPA analysis based on both weighted and unweighted UniFrac distances exhibited a shift of environmental and spatial effects on PCC variation with temporal variation. Quantification analysis of assembly processes on community turn over showed that “heterogeneous selection” dominated for PCC temporal variation, with basic abiotic parameters such as temperature, pH, ammonia nitrogen as the driving factors. Analysis of seasonal features showed that seasonal specific OTUs (ssOTUs) exhibited different seasonal attributions under the same phylum; meanwhile, the ssOTUs showed significant correlations with the driving environmental factors, which suggested that finer-level analysis was needed to more strictly reflect the temporal variation. Moreover, predicted nitrogen and sulfur metabolism were significantly shifted during the temporal variation. Our results clearly showed that seasonally varied environmental factors drive the “heterogeneous selection” process for PCC assembly in seawaters of Bohai Bay during different sampling seasons.