Award: OCE-1521597

One of the major aims of marine science is to understand how marine resources and ecosystems will change in the future. One environmental change is ocean acidification, which is the decline in seawater pH, and other aspects of ocean chemistry, associated with absorption of anthropogenic carbon dioxide emissions. Ocean acidification presents a major challenge to marine species that depend on present day or historical seawater chemistry conditions for growth and survival. For laboratory experiments testing the impact of ocean acidification on marine organisms, the lack of environmental realism may limit the predictive power of experimental results. In fact, pH varies greatly in time and space. How this natural variability in ocean chemistry alters species responses to ocean acidification is not well understood. This project assessed the influence of pH variability on the early development and physiology of the Mediterranean mussel. Specifically, the project addressed the impact of daily pH fluctuations. This variability is common in coastal environments with dominant photosynthesizing species, such as seagrass, and is relevant to the early development of mussels, which occurs over a few days. The project developed an experimental system by which to manipulate pH variability and grow mussel larvae. Technological aspects of these methods were published in order to share the methods with other research groups, and a two-day international workshop was held in France to assist research groups with implementing pH sensing technologies for both field- and laboratory-based research. The main discovery from this project was that pH variability had little effect on mussel growth but that the timing of the pH fluctuations at specific developmental time points was important. Certain developmental events were found to be pH sensitive and short in duration. If pH happened to by high, development progressed as normal, but if pH happened to be low, development progressed abnormally. This project did not find evidence for a consistent beneficial effect of natural pH variability on early mussel development. In natural systems, depending on the local pH variability, timing at which fertilization occurs may determine the success of a larval cohort and therefor contribute to more variation in future recruitment.For aquaculture, the results indicate that management of the early developmental stage, if implemented at the right time, could have a beneficial outcome for successful larval development through settlement. The project was conducted in collaboration with Prof. Todd Martz at Scripps Institution of Oceanography and Dr. Jean-Pierre Gattuso at the Oceanographic Laboratory of Villefranche in France, where the majority of the work took place. The project supported a postdoctoral fellow for two years and provided research opportunities (2-6 months in duration) for total of five students from three different countries, including one PhD student from the United States. Through this project, additional research and fellowship funding was secured for an intern, Master student, and PhD student. For the PhD project, the experimental work is complete but data analyses are on-going. Specifically, this aspect of the project is assessing the potential for genetic adaptation to ocean acidification conditions and the influence of long-term exposure to stable and variable environmental conditions on mussel physiology. Last Modified: 12/24/2017 Submitted by: Lydia Kapsenberg