Gulf of Alaska | Fishes and Fish Habitats DOCTORATE POSTER PRESENTATION Characterizing the direct and indirect effects of ocean acidification on juvenile pink salmon ( Oncorhynchus gorbuscha ) Presenter: Marina Alcantar , mwalcantar@alaska.edu, University of Alaska Fairbanks, College of Fisheries and Ocean Sciences Shelby Bacus , scbacus@alaska.edu, University of Alaska Fairbanks, College of Fisheries and Ocean Sciences Amanda Kelley , alkelley@alaska.edu, University of Alaska Fairbanks, College of Fisheries and Ocean Sciences The increase in anthropogenic carbon dioxide expelled into the atmosphere is driving a long-term decrease in ocean pH, a process known as ocean acidification (OA). Previous research has shown that OA can have direct, negative impacts on marine organisms, notably during early life stages. Additionally, food web dynamics can be altered as a consequence of OA, as lower trophic level organisms are affected which subsequently influence higher trophic level species who rely on them. This study is a fully factorial, multi-stressor experiment assessing the direct effect of elevated pCO2, and the indirect effect of reduced food availability, on newly osmocompetent juvenile pink salmon ( Oncorhynchus gorbuscha ). Juvenile pink salmon were exposed to ambient pCO2 (400 µatm)/ambient food availability (3% body mass), elevated pCO2 (1,100 µatm)/ambient food availability, ambient pCO2/reduced food availability (1.5% body mass) or ambient pCO2/reduced food availability treatments for six weeks in 2021. This study detected a significant, negative effect of elevated pCO2 on conditional index and mass. Further, assessment of the endocrine response in juvenile pink salmon showed a significant increase in cortisol expression under elevated pCO2 conditions, an increase that appears to correlate with the onset of experimental mortality. Additionally, otolith analysis revealed a relationship between time in culture vessels and the amount of the calcium carbonate polymorph vaterite present in otoliths, as well as a correlation between otolith vaterite presence and mortality in juvenile pink salmon. Routine metabolic rate (RMR) was also assessed, with a significant, positive effect on RMR correlated with elevated pCO2 exposure. These noted effects of elevated pCO2 exposure establish pink salmon juveniles as a species vulnerable to the direct and indirect effects of OA, potentially resulting in population level impacts to this valuable Alaskan species.
Alaska Marine Science Symposium 2023 179
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