Effects of low p CO 2 conditions on sea urchin larval size

Ocean acidification results from an increase in the concentrations of atmospheric carbon dioxide ( CO 2 ) impacts on marine calcifying species, which is predicted to become more pronounced in the future. By the end of this century, atmospheric p CO 2 levels will have doubled relative to the pre‐industrial levels of 280 ppm. However, the effects of pre‐industrial p CO 2 levels on marine organisms remain largely unknown. In this study, we investigated the effects of pre‐industrial p CO 2 conditions on the size of the pluteus larvae of sea urchins, which are known to be vulnerable to ocean acidification. The larval size of H emicentrotus pulcherrimus significantly increased when reared at pre‐industrial p CO 2 level relative to the present one, and the size of A nthocidaris crassispina larvae decreased as the p CO 2 levels increased from the pre‐industrial level to the near future ones after 3 days' exposure. In this study, it is suggested that echinoid larvae responded to pre‐industrial p CO 2 levels. Ocean acidification may be affecting some sensitive marine calcifiers even at the present p CO 2 level.