Biogeography of globally distributed bacteria in temperate and boreal Québec lakes as revealed by tag pyrosequencing of 16S rRNA genes

Sequence data of 16S rRNA genes reveal that many bacterial taxa are found in all freshwater lakes. However, the global data set is highly weighted toward lakes in temperate regions of North America and northern Europe, and it is unclear whether bacterial communities in other northern latitude environments, such as boreal lakes in North America, differ from those in lower latitudes. This study used pyrosequences of the 16S rRNA gene to examine bacterial diversity in 37 temperate and boreal lakes in Quebec, Canada, over the course of a year. Nearly all taxa in the global data set were also found in the Quebec lakes, but relative abundances differed. Community structure varied geographically and seasonally for 97% similar operational taxonomic units (OTUs) but not at lower levels of similarity. Seasonal shifts in community structure were larger in temperate lakes than in boreal lakes, and community structure differed between boreal and temperate lakes in summer but not in winter. The differences in taxonomic composition between temperate and boreal lakes appear to be driven mostly by environmental processes influencing community structure of temperate lakes in summer. Our results provide a baseline for interpreting impacts of climate change in boreal biomes where community structure is driven by environmental factors.