| Summary: | Thesis (Master's)--University of Washington, 2017-06 Ocean acidification (OA) is decreasing the pH of surface waters in Puget Sound, Washington, an area already prone to low pH from natural processes such as upwelling, freshwater inputs, and high respiration/decomposition rates. High rates of production and long residence times in Puget Sound can also lead to low dissolved oxygen (DO) levels (hypoxia) in some areas. Studies have shown the negative effects of these stressors on marine organisms, particularly calcifiers. I examined how changes in pH and oxygen in seawater affect adult fecundity and larval survival of the native Olympia oyster (Ostrea lurida). Through three discrete trials, I observed the following trends: Adult oysters conditioned at ~400 µatm released significantly more larvae than those conditioned at higher pCO2 levels ranging from 1000 to 2475 µatm pCO2. Larval survival decreased in two multi-stressor treatments when challenged with varying combinations of pCO2 and DO. Offspring of parents conditioned under high pCO2 experienced reduced survival when exposed to both high pCO2 and low DO (14.7% survival). In addition, progeny of adults conditioned under low pCO2 died when exposed to high pCO2 and high DO (22% survival). Our results suggest that elevated pCO2 negatively affects fecundity in O. lurida but that the synergistic effects of high CO2 and low DO on larval survival is more complicated than previously reported. Multigenerational, multi-stressor studies such as this are important in determining how species will respond to an environmental change in the ocean.
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