Spatial variability of particle-attached and free-living bacterial diversity in surface waters from the Mackenzie River to the Beaufort Sea (Canadian Arctic)

[摘要] We explored the patterns of total and active bacterial community structure ina gradient covering surface waters from the Mackenzie River to the coastalBeaufort Sea in the Canadian Arctic Ocean, with a particular focus onfree-living (FL) vs. particle-attached (PA) communities. Capillaryelectrophoresis–single-strand conformation polymorphism (CE-SSCP) showedsignificant differences when comparing river, coast and open sea bacterialcommunity structures. In contrast to the river and coastal waters, total (16SrDNA-based) and active (16S rRNA-based) communities in the open sea sampleswere not significantly different, suggesting that most present bacterialgroups were equally active in this area. Additionally, we observedsignificant differences between PA and FL bacterial community structure inthe open sea, but similar structure in the two fractions for coastal andriver samples. Direct multivariate statistical analyses showed that totalcommunity structure was mainly driven by salinity (a proxy of dissolvedorganic carbon and chromophoric dissolved organic matter), suspendedparticles, amino acids and chlorophyll a. Pyrosequencing of 16S rRNA genesfrom selected samples confirmed significant differences between river,coastal and sea samples. The PA fraction was only different (15.7%similarity) from the FL one in the open sea sample. Furthermore, PA samplesgenerally showed higher diversity (Shannon, Simpson and Chao indices) than FLsamples. At the class level, Opitutae was most abundant in the PAfraction of the sea sample, followed by Flavobacteria andGammaproteobacteria, while the FL sea sample was dominated byAlphaproteobacteria. Finally, for the coast and river samples andboth PA and FL fractions, Betaproteobacteria,Alphaproteobacteria and Actinobacteria were dominant. Theseresults highlight the coexistence of particle specialists and generalists andthe role of particle quality in structuring bacterial communities in thearea. These results may also serve as a basis to predict further changes inbacterial communities should climate change lead to further increases inriver discharge and related particle loads.

[学科分类] 地球化学与岩石