Comparative study on effects of different seawater acidification scenarios on embryogenesis and larval spicule development of the sea urchin Hemicentrotus pulcherrimus

To compare the effects of CO2-induced seawater acidification and HCI-induced seawater acidification on benthic echinoderms, Hemicentrotus pulcherrimus inhibiting intertidal coastal zone in northern China was utilized in the current study. Under two seawater acidification scenario conditions, embryogenesis and larval spicule development were investigated and compared, respectively. Based on the projection of IPCC, present natural seawater condition （pH=8.06 ± 0.01） and six laboratory-controlled acidified conditions （three CO2-treated groups and three HCI-treated groups, respectively） were set up. Results showed that： （a） early embryonic cleavage tended to be delayed as pH declined in all acidified seawater groups, embryonic cleavage delay of CO2-treated groups tended to be more severe as compared to that of HCI-treated groups; （b） impaired larval symmetry were observed both in CO2-treated groups and HCI-treated groups, there was no significant difference between the two; （c） alteration in skeletal elements was observed in all acidified groups as compared to control, and elongated spicules were observed in CO2-treated groups and shorten spicules were found in HCI-treated groups. Also, when A pH=-0.5, spicule corrosion in CQ-treated group was worse than that in HCI-treated group. All data observed in this study suggest that different seawater acidification scenarios had different effects on sea urchins. Compared to HCI-induced seawater acidification, the effects of CO2-induced seawater acidification on sea urchins were more profound.