Gulf of Alaska | Climate and Oceanography
The impact of glacial inputs on marine microbial communities in Alaska’s coastal margins Presenter: Gwenn Hennon , gmhennon@alaska.edu, University of Alaska Fairbanks Megan Brauner , mbrauner@alaska.edu Jacob Cohen , jecohen@alaska.edu, University of Alaska Fairbanks
Emily Williamson , erwilliamson3@alaska.edu, University of Alaska Fairbanks Emily Whitney , ejwhitney@alaska.edu, University of Alaska Southeast Jason Fellman , jbfellman@alaska.edu, University of Alaska Southeast
Alaska’s coastal margins support a range of habitats for intertidal species, forage fish and marine mammals that are crucial to the ecosystem’s function and services. Inputs of inorganic nutrients and dissolved organic matter (DOM) from watersheds surrounding these coastal systems fuel marine primary and secondary production, which in turn support the food web. Glacial and non-glacial watersheds have different biogeochemical fingerprints, with glacial rivers having lower concentrations of inorganic nitrogen and more bioavailable DOM compared with watersheds fed by forested areas. Here, we present data on the seasonal and spatial patterns of marine microbial community composition over a glacial watershed gradient in Lynn Canal and Kachemak Bay, Alaska from 2020-2021. Transitions in phytoplankton community composition were correlated with seasonal shifts in marine temperature, salinity, and nutrient concentrations as expected. However, community composition changes were not significantly correlated with glacial cover of the upstream watersheds, likely due to estuarine circulation integrating multiple source waters. Additionally, we present results of a week-long incubation experiment in Lynn Canal in 2021 testing the impact of glacial v. non-glacial freshwater inputs on marine microbial communities. We found a significant decrease in total dissolved nitrogen concentrations and an increase in dissolved organic carbon concentrations and nanophytoplankton abundance in incubations with the addition of non-glacial river water. It is predicted that glaciers will continue to recede in these regions suggesting that a shift towards non-glaciated watersheds may increase primary production and alter microbial community composition in Alaska’s coastal margins, with unknown implications for coastal marine food webs and ecosystem services.
Alaska Marine Science Symposium 2023 107
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