Abstract
From July to August 2010, the IBRV ARAON journeyed to the Pacific sector of the Arctic Ocean to monitor bacterial variation in Arctic summer surface-waters, and temperature, salinity, fluorescence, and nutrient concentrations were determined during the ice-melting season. Among the measured physicochemical parameters, we observed a strong negative correlation between temperature and salinity, and consequently hypothesized that the melting ice decreased water salinity. The bacterial community compositions of 15 samples, includicng seawater, sea-ice, and melting pond water, were determined using a pyrosequencing approach and were categorized into three habitats: (1) surface seawater, (2) ice core, and (3) melting pond. Analysis of these samples indicated the presence of local bacterial communities; a deduction that was further corroborated by the discovery of seawater- and ice-specific bacterial phylotypes. In all samples, the Alphaproteobacteria, Flavobacteria, and Gammaproteobacteria taxa composed the majority of the bacterial communities. Among these, Alphaproteobacteria was the most abundant and present in all samples, and its variation differed among the habitats studied. Linear regression analysis suggested that changes in salinity could affect the relative proportion of Alphaproteobacteria in the surface water. In addition, the species-sorting model was applied to evaluate the population dynamics and environmental heterogeneity in the bacterial communities of surface mixed layer in the Arctic Ocean during sea-ice melting.
Highlights
During summer, water from the north Pacific enters the Arctic Ocean after passing through the Bering Strait, intermixing with freshwaters from melting ice
Microbial communities in the surface waters would be affected by environmental changes resulting from melting sea-ice because the amount of sea-ice is dramatically reduced in this area during summer
The aims of this study were to examine the composition of the bacterial community in Arctic marine environments and to understand the population dynamics of bacterial communities in surface water mixing with fresh water
Summary
Water from the north Pacific enters the Arctic Ocean after passing through the Bering Strait, intermixing with freshwaters from melting ice. Microbial communities in the surface waters would be affected by environmental changes resulting from melting sea-ice because the amount of sea-ice is dramatically reduced in this area during summer. The species-sorting model of the metacommunity concept describes variation in the abundance and composition of bacterial communities. If the species-sorting process is effective, different bacterial communities should be found in different habitats. Species-sorting effects on bacterial community composition can be relatively weak when other metacommunity aspects, such as the source-sink dynamics and neutral model, operate at the same time. The speciessorting process may be influenced by other elements during the formation of a bacterial community, or it may depend on how many generalist (commonly occurring in the surrounding habitat regardless of environmental conditions) and specialist (habitatspecific) taxa are present in a community [5]
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