Harnessing computational genomics to explore the dynamics of rapid adaptation to ocean acidification

Accurately forecasting biological responses to global ocean change hinges upon understanding the capacity for marine species to adapt in response to the shifting abiotic environment. Emerging methods from computational genomics provide a promising, and increasingly affordable, means to quantify levels of adaptive genetic variation within natural populations, thereby providing a proxy for this adaptive capacity. By linking the phenotypic and physiological traits affected by global change stressors to their underlying genetic basis, it is possible to probe the extent to which these traits may evolve under an ocean global change scenario. I will discuss a cross-disciplinary study that combined an extensive lab-based experiment with high-throughput sequencing to determine the capacity of the marine mussel, Mytilus galloprovincialis, to adapt to extreme and abrupt changes in seawater pH. Specifically, we tracked the shell size distribution and frequency of 30,000 single nucleotide polymorphisms of a single, and genetically diverse, larval population of M. galloprovincialis in ambient (pH_T = 8.1) and extreme low pH conditions (pH_T = 7.4) from the embryo stage through settlement. Additionally, we separated larvae by size to link a fitness-related trait to its underlying genetic background in each treatment. Our phenotypic and genetic data illuminate a reservoir of standing variation within the species to adapt to reductions in seawater pH. We further demonstrate that unique genotypic groups are associated with accelerated shell growth in the ambient and low pH treatments. Lastly, we report a resulting list of candidate genes that will be putatively under selection as ocean acidification progresses, as well as ongoing functional validations (utilizing qPCR and in situ hybridizations) to affirm these candidates.