Ocean Acidification/Collaborative Research/RUI: Effects of Ocean Acidification on Larval Competence, Metamorphosis, and Juvenile Performance in a Planktotrophic Gastropod

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Levels of CO2 in the air are now about 40% higher than they were 200 years ago at the start of the Industrial Revolution. At least 1/3 of excess CO2 production has been absorbed by the ocean, making it more acidic as the CO2 forms carbonic acid. Understanding the likely impact of this increasing ocean acidification (OA) on marine animals and ecosystems is complicated by the fact that other features of the environment are also expected to change appreciably (e.g., seawater temperatures will increase and food availability and nutritional value may decline), by the fact that stresses experienced in early development can have lasting effects, and because the molecular mechanisms of the responses are poorly understood. This study examines how OA under different environmental conditions will impact the development, dispersal, and metamorphosis of the marine snail Crepidula fornicata, a common species native to the eastern U.S. that has now become established in the Pacific Northwest, Europe, and elsewhere. This study will include: 1) the impact of OA on relative rates of tissue and shell growth in larvae; 2) long-term impact of larval exposure to OA on the survival and growth of juveniles; 3) influence of OA on gene expression patterns in both larvae and juveniles; 4) impact of OA on time until metamorphosis and on the ability to metamorphose in response to environmental inducers; 5) effect of elevated temperature on responses to OA; 6) impact of larval diet on vulnerability to OA; and 7) impact of OA on larval swimming ability and settlement behavior. The study species is native to the East coast of the United States but has now become an important invasive in many other parts of the world. The results will have important implications for understanding the continued spread of this species. In addition, the work includes opportunities for graduate and undergraduate student training, outreach to high school teachers and development of new classroom exercises. Molluscan larvae are expected to be especially susceptible to the effects of ocean acidification (OA) in the coming years, due to their thinly calcified shells. In addition, water temperatures are expected to amplify some impacts of OA. Some effects, such as potentially reduced growth rates, reduced shell thickness, and altered dispersal capability are likely to be immediate, while others (latent effects) may appear only later in development, well after metamorphosis has taken place. In addition, OA--with or without ocean warming--may alter larval behavior and physiology in ways that affect the timing of metamorphosis and the fitness of juveniles,thus altering dispersal potential and vulnerability to predators. OA may also alter the abundance and nutritional quality of phytoplankton. We will investigate the consequences of OA under different environmental scenarios for larvae of the marine gastropod Crepidula fornicata, an easily cultured species that is receiving increasing attention both as a general model for lophotrochozoan development and as an ecologically significant invader in benthic subtidal communities. Our study will include: 1) impact of OA on rates of larval tissue and shell growth; 2) latent effects of larval exposure to OA on juvenile survival and growth; 3) effect of elevated temperature on responses to OA; 4) influence of elevated OA on larval and juvenile gene expression; 5) impact of OA on the development of competence for metamorphosis; 6) impact of OA on the response of competent larvae to a variety of metamorphic inducers; 7) impact of larval diet quality on vulnerability to OA, both in the larval stages and following metamorphosis (latent effects); and 8) impact of OA on larval swimming and settlement behaviors, and the neural correlates of those behaviors.