Effects of climate change induced ocean acidification and low oxygen on larval rockfish

• Main Author: Kristin Saksa
• Other Authors: Scott Hamilton, Cheryl Logan, Susan Sogard, Gitte McDonald
• Format: Master Thesis
• Language: English
• Published: Moss Landing Marine Laboratories 2021
• Subjects: Ocean acidification
• Online Access: https://hdl.handle.net/20.500.12680/k930c368p

"A thesis presented to the faculty of Moss Landing Marine Laboratories." ABSTRACT: The California Current ecosystem is experiencing dramatic changes in ocean chemistry resulting in ocean acidification (i.e., decreasing pH) and lower dissolved oxygen [DO] levels. These changes are exacerbated by increases in upwelling intensity and the shoaling of the oxygen minimum zone. Gopher rockfish (Sebastes carnatus) and blue rockfish (Sebastes mystinus) are ecologically and economically valuable rockfish species, whose habitat is becoming increasingly inundated with low pH and low DO water. To test how ocean acidification and hypoxia may interact to influence the reproductive process in rockfishes, I exposed gravid females of both species to four treatments throughout the gestation period: 1) low pH (7.5); 2) low DO (DO 4.0 mg/L); 3) combined stressor (7.5 pH x DO 4.0 mg/L); and 4) control (~8.0 pH x ~DO 8.0). Post-parturition, larvae from each brood were seeded into each of the four treatments to evaluate survivorship, metabolism, and hypoxia tolerance as a function of the prior maternal treatment conditions and the subsequent larval treatment. I assessed the impact of maternal rockfish exposure to climate change stressors on fecundity, percent deformity, and larval morphology. My research indicates that Gopher rockfish larvae are resilient to low pH (pH 7.5) and low DO (DO 4.0mg/L) based on both maternal and larval exposures to these stressors. Gopher rockfish may be adapted or acclimatized to gestating in these conditions because their reproductive season overlaps with Spring upwelling on the central California coast. Blue rockfish also exhibited resiliency; larval survivorship, metabolic rate, hypoxia tolerance, and percent deformity were not impacted by low pH, low DO or combined stressor. However, blue rockfish larval morphology was impacted by gestating in the combined stressor treatment, resulting in a reduction in larval eye size. Adult blue rockfish peak reproductive season is in winter and they may not be as ...