| Summary: | Thesis (M.S.) University of Alaska Fairbanks, 2022 One of the consequences of anthropogenic carbon emissions is ocean acidification (OA). As atmospheric concentrations of carbon dioxide (CO₂) continue to rise, oceanic absorption of CO₂ changes the balance of dissolved inorganic carbon species (DIC) in seawater and alters marine carbonate chemistry. OA is predicted to be more pronounced in high-latitude environments, highlighting the importance of characterizing nearshore carbonate chemistry in polar and subpolar habitats, such as Alaska's marginal seas. OA can have significant impacts on calcifying organisms (including pteropods, clams, mussels, and oysters), lowering the saturation of calcium carbonate minerals that are essential for shell formation in seawater. Despite the economic, subsistence, and cultural importance of vulnerable Alaskan marine biota, to date there are limited in situ data tracking the nearshore carbonate chemistry fluctuations of coastal Alaskan waters. To address this knowledge gap, this study's research goal is to compare, in highfrequency resolution, the seasonal carbonate chemistry fluctuations in two representative nearshore Alaskan ecosystems: Kaktovik Lagoon (Arctic Ocean) and Kachemak Bay (Gulf of Alaska). Moored sensors detected pH, temperature, salinity, and O₂ data to characterize which physicochemical variables have the greatest average contributions to site-specific pH variability across one year (September 2018-August 2019) in these two regions. Analyses of the annual time series from both regions revealed interregional disparities, especially related to seasonality, biotic activity, and physicochemical fluctuations in the seawater. The pH dynamics of the Kachemak Bay mooring sites demonstrated a strong connection to a seasonal biotic signal, specifically through the push-pull effect of photosynthesis and respiration on DIC. Kaktovik's pH dynamics suggested an interplay among salinity, biotic activity, and seasonal ice coverage. Both regions demonstrated high pH ...
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