Carry-over effects of ocean acidification in a cold-water lecithotrophic holothuroid

Ocean acidification (OA) due to anthropogenic CO2 emissions is predicted to affect the world's oceans in the near future. To date, knowledge remains limited on the response of species that are weakly calcified, produce lecithotrophic (non-feeding) larvae and live in polar/subpolar environments. The cold-water sea cucumber Cucumaria frondosa represents an ideal model for such investigations. One of the most abundant echinoderms in the world, it is annually-spawning, slow-growing and has been commercially exploited in the North Atlantic for over 35 yr. The present study examined the effects of predicted near-future OA scenarios on gametogenesis, spawning and embryonic development of C. frondosa, as well as on processes that may compete or coincide with reproductive effort such as ossicle formation and lipid synthesis. Sea cucumbers were exposed to a 0.4 unit pH decrease over 19 wk using a fully open flow-through design allowing for natural fluctuations in pH, light, temperature, salinity and nutrient levels. There were 2 treatment groups, ambient pH (7.9-8.2; pCO(2) 430-470 mu atm) and low pH (7.5-7.7; pCO(2) 1330-1530 mu atm). Results indicate that low pH/high pCO(2) interferes with gamete synthesis, leading to discrepancies in oocyte/embryo buoyancy and morphology and developmental tempo, translating into 100% mortality before the blastula stage. Differences in the microstructural appearance of ossicles and the lipid contents of muscles, gonads and spawned oocytes were also highlighted. Such findings draw attention to previously understudied impacts of OA, including transgenerational effects in cold-water species with maternally provisioned eggs, and the resulting implications for temperate, subpolar and polar ecosystems.