Robustness of Paracentrotus lividus larval and post-larval development to pH levels projected for the turn of the century

Abstract

Ocean acidification is causing changes to the chemistry and biology of the marine environment, in ways that we are only just beginning to understand. Growing evidences demonstrate that ocean acidification can influence the survival, growth, development, and physiology of marine invertebrates. Here, we assessed the impact of ocean acidification on the sea urchin Paracentrotus lividus larval development (from embryos exposed to experimental conditions from the 24 h gastrula stage to 35 days) and settlement. Samples were collected from the Canary Islands (28°24′N, 16°18′W) in March 2012. Three pH treatments were tested: (1) pH 8.1, the present average pH; (2) pH 7.7, the average predicted for the year 2100, but already experienced in the natural environment during extremes of variability; and (3) pH 7.4, predicted extremes of natural variability by 2100. The mortality rate was significantly increased by 40 % at the lowest pH. Time required by larvae to achieve each developmental stage (from gastrula to competent stage) was decreased at pH 7.7 (larval development speed increased by 18 %), but larval morphology at a given size did not differ from the other pH treatments. Settlement was delayed by 8 days at pH 7.7 compared to pH 8.1, and no settlement was observed at pH 7.4. Overall, only sublethal effects were observed in larvae exposed to pH 7.7, while pH 7.4 induced both lethal and sublethal effects. Our results support the hypothesis that P. lividus is robust to survive in an environment with the present natural variation. However, the species is sensitive to extreme levels of pH that are predicted within the next 90 years.