The effects of ocean acidification on walleye pollock ( Theragra chalcogramma) early life history stages

Since the Industrial Revolution of the late 1700’s, atmospheric and marine carbon dioxide levels have drastically increased. Ocean acidification is the result of the shift in the marine carbon cycle caused by the increase in marine and atmospheric carbon dioxide. Changing environmental conditions caused by ocean acidification have been shown to have adverse effects on different marine species as well as life history stages. As a result, ecologically and economically important teleost fish species such as walleye pollock (Theragra chalcogramma ) could be adversely affected by ocean acidification conditions. This study explores the responses of walleye pollock eggs and larvae incubated under different projected levels of ocean acidification, looking at hatch timing and growth parameters to examine potential adverse responses to more acidic conditions. Older walleye pollock juveniles (age 1+) were used to uncover potential physiological responses to ocean acidification pertaining specifically to stress, overall body condition indices, and blood chemistry. I found that while the two early life history stages of walleye pollock could survive under ambient, high, medium, and low pH conditions (pH 8.1, 7.9, 7.6, and 7.2, respectively), there were some physiological responses to projected levels of ocean acidification. Hatch timing was not delayed in the lowest pH treatment as expected. In addition, size at hatch, yolk area, and eye diameter did not differ among pH treatments. Walleye pollock juveniles reared under projected levels of ocean acidification demonstrated shifts in blood gas levels and blood pH. However, exposure to a lower pH environment of pH 7.9, 7.6, or 7.2 did not induce a response for either the stress indicators or body condition indices that were measured. To uncover the mechanism for their resilience, more testing is needed to gain further insight into underlying compensatory mechanisms of various life history stages and populations.

Fernandez E. R., 2014. The effects of ocean acidification on walleye pollock ( Theragra chalcogramma) early life history stages. MSc thesis, University of Alaska Fairbanks, 95 pp. Thesis (subscription required).

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