Effects of ocean acidification on juveniles sea urchins: Predator-prey interactions

Increasing CO2 concentration in the atmosphere during the last decades has led to a significant decrease in ocean pH. Organisms that need carbonate to build their calcareous skeletons could be severely affected. In this study we focused on the effects of ocean acidification on juveniles of the sea urchins Paracentrotus lividus and Diadema africanum. We assessed the effects of decreased pH on two skeletal structures, spines and test, and their impacts on species performance to avoid predation events in the field. Juveniles of both study species were exposed for 100 days to two treatments of pH: a pH of 8.0 (413.2 μatm) and pH of 7.6 (1349 μatm). Our results showed that D. africanum juveniles from the acidic treatment were more predated than those kept in the control treatment. These differences were not observed between treatments in P. lividus. Diadema africanum may be more sensitive to the indirect effects of ocean acidification on predator avoidance than P. lividus. However juveniles reared in a pH of 7.6 showed changes in shape in skeletal structures in both species. Considering these results in future scenarios, P lividus may be considered a “winning species”, and D. africanum a “losing species” in the climate change stake.