Microbial dynamics in the Arctic Chukchi Sea : differences in microbial abundance and bacterial community composition in high and low production regimes
Hodges, Lisa Renee
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This research examines the importance of bottom-up and top-down controls on bacterial abundance and community composition during summertime production in the coastal Arctic Ocean. Bacterial and viral abundance, bacterial community composition, and free-living (3 µm-filtered, FL) and particle-associated (unfiltered, FL+PA) assemblages were examined in the Chukchi Sea during August 2000. Nutrients, chlorophyll a, and particulate organic matter (POM) were also measured. Bacteria were isolated and analyzed by DGGE, 16S rDNA sequence analysis, and for substrate utilization. Increased bacterial and viral abundance, decreased species richness, and decreased similarity (Sorenson’s Index) between FL and PA assemblages occurred in high versus low POM regions. Bacterial abundance, species richness, and Sorenson’s Index correlated best with POM, while viral abundance correlated best with bacterial abundance. Algal bloom conditions producing high POM concentrations may therefore increase bacterial and viral abundance, reducing species richness, and promote differences between FL and PA assemblages.