Natural Variation and Evolutionary Responses to Climate Change Stressors in Marine Invertebrates

Our rapidly changing climate is putting many species at risk of extinction and there is an urgent need to understand how species will respond to these changes. In this dissertation, I evaluate how three species of marine invertebrates (corals, oysters, and copepods) respond to stressful conditions in their current environments and how plasticity and evolutionary adaptation could alter their response to future climate change stressors. I first employed a space for time study to elucidate population differences in the response of cold-water corals, Balanophyllia elegans, to future ocean acidification. I found evidence that upwelling history (natural low pH exposure) influences the physiological and transcriptomic response of B. elegans to laboratory low pH exposure. I found that populations that naturally experience low pH (due to more frequent upwelling events) may be more tolerant to future ocean acidification. I also used a space for time study on two Louisiana populations of the eastern oyster, Crassostrea virginica, and found evidence of local adaptation and plasticity that influences their response to stressful low salinities. The population that naturally experiences high salinity was unable to maintain growth in low salinity conditions and employed a different plastic response to the low salinity population. Finally, I used a combination of quantitative genetics and experimental evolution studies to identify standing genetic variation in populations of C. virginica, and the species as a whole, involved in tolerance to current and potentially future stressful environments. I show that the two Louisiana populations of C. virginica have ample genetic variation for selection to act on and that they are capable of adapting to low salinity. I also demonstrate the use of hybridization and experimental evolution to increase the fitness of the copepod, Tigriopus californicus, to future warming scenarios. In my dissertation, I have contributed to our knowledge of how marine invertebrates respond to stressors in their environments which will inform conservation efforts under future climate change scenarios