MEPS 578:87-97 (2017)  -  DOI: https://doi.org/10.3354/meps12227

ABSTRACT: Solar-powered animals are particularly susceptible to climate change because photosynthesis brings major risks to animals under environmental stress. Although some groups have been widely studied (e.g. corals), little information is available on how other less charismatic photosynthetic animals (e.g. sea slugs) will respond to future ocean conditions. This study is the first to evaluate the impact of future ocean conditions on the fitness of tropical photosynthetic sacoglossan sea slugs throughout different life stages. Adults of Elysia clarki were exposed (30 d) to conditions simulating present-day and predicted scenarios of ocean acidification (ΔpH = 0.4) and warming (+4°C). Egg masses were incubated under the same conditions as adult broodstock until 15 d after metamorphosis. Exposure to ocean acidification and warming scenarios led to a significant decrease in the number of spawned egg masses and in their membrane thickness. Moreover, a significant decrease in the volume of embryo capsules was accompanied by an increase in embryo volume. These findings suggest that sea slugs shifted their energy allocation towards embryo quality rather than to structures that confer protection from environmental challenges. Climate change-related stress significantly reduced the survival and length of veligers and increased the incidence of deformities, but did not affect chloroplast acquisition by juvenile slugs. The lower reproductive output of adults and the adverse impacts on early life stages recorded under future ocean conditions allows us to anticipate negative consequences for the recruitment of these sea slugs’ populations in the oceans of tomorrow.

KEY WORDS: Acidification · Warming · Sacoglossan sea slugs · Ontogenetic development · Growth · Malformations · Chloroplast acquisition