Drivers of Regional Bacterial Community Structure and Diversity in the Northwest Atlantic Ocean.
Zorz J, Willis C, Comeau AM, Langille MGI, Johnson CL, Li WKW, LaRoche J
Front Microbiol. 2019. doi: 10.3389/fmicb.2019.00281
The authors of this study analyzed the effects of physicochemical gradients on bacterial community structure. They sequenced the V6V8 hypervariable region of the 16S rRNA gene to characterize the bacterial community of the Scotian Shelf sector of the Northwest Atlantic Ocean during spring and fall of 2014 and 2016. They collected 451 water samples which were categorized based on:
- Season: Spring or fall
- Depth: Surface, Photic or Deep
- Geographic position: On-shelf, Shelf break or Off-shelf
- Size fraction: Particle-associated (PA) bacteria or Free-living (FL) bacteria.
They also measured the temperature, salinity, and O2 concentration conditions.
The main objective of this study was to understand the factors that could change the microbial community structure and biodiversity across multiple features such as depth and season.
Bacterial concentrations decreased steadily with depth but were significantly higher in the fall than in the spring
Alphaproteobacteria and Gammaproteobacteria were the dominant taxa in the FL category, in both spring and fall samples and all depths
The PA size fraction was enriched in select bacterial taxa within Flavobacteriia, Deltaproteobacteria, Verrucomicrobiae, Saprospirae, and various classes of Planctomycetes
Temperature had the strongest correlation with the entire PA community, while oxygen had the strongest correlation with the entire FL community.
Bacteria preferentially found in the spring are likely copiotrophs able to achieve high growth rates in favorable conditions, whereas bacteria preferentially found in the fall could be considered oligotrophs with growth strategies adapted to low nutrients.
Cyanobacteria were the main taxa found more often in the fall.
In conclusion, this study provides a baseline description of the bacterial community structure on the Scotian Shelf and how it is correlated with environmental factors as salinity, temperature or dissolved oxygen.