Gulf of Alaska | Lower Trophic Levels DOCTORATE POSTER PRESENTATION Co-occurrence networks of marine microbes in the northern Gulf of Alaska Presenter: Megan Brauner , mbrauner@alaska.edu Jacob Cohen , jecohen@alaska.edu, University of Alaska Fairbanks Brandon Briggs , bbriggs6@alaska.edu Gwenn Hennon , gmhennon@alaska.edu, University of Alaska Fairbanks
Microbial ecologists have long focused on competitive interactions between microbes, such as competition for a limiting resource. However, there is building evidence that many microbes have equally important beneficial interactions such as mutualism and commensalism that are crucial for supporting primary production. We hypothesize that phytoplankton and bacterial taxa will rely more heavily on these mutualistic or commensal interactions when nutrients (such as nitrate or iron) are limiting. We can test this hypothesis by leveraging the new wealth of DNA sequencing data from the Northern Gulf of Alaska (NGA) by creating co-occurrence networks where positive correlations between abundance of microbes indicate potential beneficial interactions within microbial communities. Water samples were collected from three onshore to offshore transects from Seward, Kodiak, and Middleton Island as part of the NGA-LTER program and from estuaries in Juneau and Kachemak Bay as part of the EPSCoR Fire and Ice program. DNA was extracted and amplified for the 16S (V4) and 18S (V9) rRNA genes and sequenced using the Illumina MiSeq and processed with the QIIME2 pipeline. Co-occurrence networks of amplicon sequence variants (ASVs) were constructed using statistically significant Spearman rank correlations (> 0.8, Bonferroni corrected p < 0.01). Our initial analysis identified over 840 bacterial nodes with 4335 edges representing significant positive correlations, which can be indicative of mutualistic interactions. We plan to use these analyses to identify keystone microbial species and investigate how these co- occurrence networks change across gradients of nutrient limitation in the NGA.
Alaska Marine Science Symposium 2023 133
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