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UBC Theses and Dissertations

The effect of climate change-related environmental acidification on the growth, development and energetics of the early life stages of pink salmon (Oncorhynchus gorbuscha) Ou, Michelle


As a consequence of increasing atmospheric CO₂, the partial pressure of CO₂ (pCO₂) in the oceans is rising, causing a decrease in pH and carbonate ions known as ocean acidification (OA). Since freshwater systems have the same potential for atmospheric equilibrium with CO₂, similar scenarios of acidification will occur in freshwater, yet little is known about the potential impacts of climate change-related acidification on freshwater species and ecosystems. Moreover, virtually no research has investigated the effect of oscillating pCO₂ tensions on fish, which are more likely to reflect natural coastal conditions. The goal of this thesis is to address some of these knowledge gaps by studying the potential effects of climate change-related acidification on pink salmon (Oncorhynchus gorbuscha) at a sensitive and critical life-stage during development in both freshwater and seawater under future elevated and fluctuating pCO₂ tensions (freshwater: 400 μatm, 1000 μatm, 2000 μatm, 400-2000 μatm (over 24hr); seawater: 400 μatm, 1600 μatm, 400-1600 μatm). Growth, production efficiencies and aerobic scope were measured starting 2 weeks pre-hatch in freshwater up until 2 weeks post-seawater transfer. Growth was reduced during freshwater rearing and following seawater transfer. Specifically, size, production efficiencies and absolute growth rates were reduced at freshwater tensions of 1000 and 2000 μatm and seawater tensions of 1600 μatm. However, no significant effects on growth were seen in response to oscillating pCO₂ tensions. Similarly, aerobic scope was reduced at high pCO₂ following seawater transfer through a reduction in maximal oxygen consumption rate (ṀO₂max) (but not routine (ṀO₂routine)), indicating that exercise in pink salmon fry may be particularly affected by climate change-related acidification. Given that control fish exhibit a dramatic increase in ṀO₂max 7 days post-seawater transfer, which is likely associated with a change in life history from a sedentary to a migratory stage, elevations in seawater pCO₂ may have implications for their seaward migration success. Overall, this thesis demonstrates that pink salmon, under predicted future increases in pCO₂, may be faced with sublethal impacts of acidification on various aspects of their physiology at a very critical time in their life history.

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Attribution-NonCommercial-NoDerivs 2.5 Canada