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Advances in nucleic acid sequencing technology are removing obstacles that historically prevented use of genomics within ocean change biology. As one of the first marine calcifiers to have its genome sequenced, purple sea urchins (Strongylocentrotus purpuratus) have been the subject of early research exploring genomic responses to ocean acidification, work that points to future experiments and illustrates the value of expanding genomic resources to other marine organisms in this new 'post-genomic' era. This review presents case studies of S. purpuratus demonstrating the ability of genomic experiments to address major knowledge gaps within ocean acidification. Ocean acidification research has focused largely on species vulnerability, and studies exploring mechanistic bases of tolerance toward low pH seawater are comparatively few. Transcriptomic responses to high pCO₂ seawater in a population of urchins already encountering low pH conditions have cast light on traits required for success in future oceans. Secondly, there is relatively little information on whether marine organisms possess the capacity to adapt to oceans progressively decreasing in pH. Genomics offers powerful methods to investigate evolutionary responses to ocean acidification and recent work in S. purpuratus has identified genes under selection in acidified seawater. Finally, relatively few ocean acidification experiments investigate how shifts in seawater pH combine with other environmental factors to influence organism performance. In S. purpuratus, transcriptomics has provided insight into physiological responses of urchins exposed simultaneously to warmer and more acidic seawater. Collectively, these data support that similar breakthroughs will occur as genomic resources are developed for other marine species.

Increasing terrestrial runoff due to anthropogenic activities has become a major problem for coral reef ecosystems around the world. Turbidity due to runoff can reduce light availability (via nutrient enrichment and sedimentation) and influence the biology and ecology of coral reefs. In this study, we explored the physiology and acclimatization potential of Porites rus , a morphologically variable reef-building coral that is common in Moorea, French Polynesia, and a species that thrives across turbidity gradients driven by proximity to terrestrial runoff. We compared tissue biomass, Symbiodinium identity, Symbiodinium density, chlorophyll concentrations, and stable isotope ratios in plating and branching areas of colonies sampled in turbid and non-turbid environments. A reciprocal transplant experiment (RTE) was also employed to compare the acclimatization capacity of P.rus from turbid and non-turbid environments. Our results indicate that the physiological differences between plating and branching regions within individual colonies of P. rus are greater than those of colonies from turbid and non-turbid environments. Plating regions of colonies had larger tissue biomasses than branching areas, regardless of environment. Plating regions also had higher chlorophyll concentrations than branching regions at the non-turbid site. The densities and genetic identity of Symbiodinium were the same at both sites. At the turbid site, δ 13 C signatures were lower in plating than branching regions of the colony, suggesting they exhibit different rates of photosynthesis and/or capacity for heterotrophy. δ 15 N were similar across sites and between morphologies, indicating that colonies from both sites were feeding at similar trophic levels and utilizing similar nitrogen sources. The RTE showed that P. rus acclimatizes differently when transplanted to the turbid and non-turbid environments. Corals from the non-turbid site grew less when transplanted to the turbid site, whereas corals from the turbid site showed no change in growth regardless of transplant location. Coral fragments transplanted to the non-turbid site, had lower levels of chlorophyll per tissue area than fragments transplanted to the turbid site, most likely reflecting the higher light levels at this site. Thus, our results demonstrate that there is significant variation in the physiology of P.rus at the colony level (branching vs. plate regions) and at the site level (turbid vs. non-turbid) and that this species can acclimatize to changes in environmental conditions on short time scales (weeks). This acclimatization potential may play an important role in enabling this coral species to diversify strategies for energy acquisition within the colony and facilitate persistence in turbid environments.