Microbial Comparison of Anoxic Saanich Inlet and Oxic Hood Canal using 16S Community Analysis

Abstract

Microbes play a critical role in the marine environment. They cycle nutrients, fix carbon, and can severely alter the water chemistry. Around the world, a place that they are especially important is in marine oxygen minimum zones (OMZs) where some are able to use alternative electron receptors other than oxygen and make up a majority of the organisms in these regions. This study compares the microbial community and water chemistry of Saanich Inlet and Hood Canal. Saanich Inlet is a seasonally anoxic fjord located on the southern tip of Vancouver Island and Hood Canal is a fjord located in the Puget Sound. Bacterial counts were taken throughout the water column at each location and compared to the water chemistry. 16S genome analysis was done to determine the microbial community composition. Bacterial concentrations and the water profile of the two locations showed that Hood Canal was fairly consistent throughout the water column, however Saanich Inlet had multiple regimes and showed a large change in chemistry at 100m depth where the oxygen approached 0 mg/L. This difference was corroborated by the genomic results that showed microbial community differences that could be explained by the oxygen deficiency and the metabolic characteristics of the dominant groups in each location. We found that Saanich Inlet was dominated by the sulfur oxidizing clade of chemolithoautotrophic bacteria SUP05 whereas Hood Canal was dominated by the Heterotrophic clade of bacteria SAR11. These results show how as OMZs grow, newly anoxic regions may show a shift in their microbial communities.