The Impact Of Ocean Acidification On Larval Development In Sea Urchin Strongylocentrotus Intermedius

Ocean acidification(OA) after ‘Warm House’ is another global environmental problemcaused by increasing emissions of anthropogenic carbon dioxide(CO2). Ongoing oceanacidification increasingly affects marine ecosystems and commercial fisheries by changingseawater pH and CaCO3saturation. On one hand, ocean acidification as an environmentalstressor could destroy internal acid-base homeostasis of marine life. On the other hand, thedecrease of seawater pH and CaCO3saturation caused by ocean acidification would affect theformation of carbonate shell and the process of biomineralization of marine life because of thechange of dynamic balance of ocean CO2—carbonate system.The objectives of this study are to investigate the impact of ocean acidification on larvalgrowth, morphology and calcification in the sea urchin Strongylocentrotus intermedius, andaccess the potential threat of ocean acidification to commercial industry of the sea urchin S.intermedius. To achieve our objectives, we firstly invented a laboratory experimental system sothat CO2-driven OA can be simulated under lab conditions. According to the fouth report ofIPCC—OA scenarios project a ΔpH=–0.3to–0.5units by the end of this century, three differentsea water pH level treatments were set up in this study: natural sea water pH－0.3units(OA1),natural sea water pH－0.4units(OA2) and natural sea water pH－0.5units(OA3). Laboratory OAscenarios experiments to study the impact of OA on larval floating rate, survival rate, larvalmophology, spicule calcifiction and spicule morphology in sea urchin S. intermedius werecarried out. Our results showed that:1、The progressive uptake of CO2can significantly increase the partial pressure of CO2(pCO2) and reduce sea water pH value. As well, over-emission of CO2can alter the dynamicequilibrium of ocean CO2—carbonate system by increasing the concentrion of hydrogencarbonate([HCO3-]), decreasing the abundance of carbonate ion(CO32-).2、Compared to the embryos cultured in natural seawater, the floating rate of each OAtreatments(OA1, OA2and OA3) did not change significantly. With the reduction of seawater pH,the survival rate of S. intermedius larvae in each OA treatments were20.00±6.00%(OA1),14.00±3.46%(OA2) and9.33±7.02%(OA3), respectively, the reduction was statisticallysignificant comparing to natural seawater group. Moreover, we found that the body symmetry ofS. intermedius larvae was affected by acidified seawater to some extent.3、By measuring total length(TL), the length of body rod (BR)and the length of post oralarm(PO), we found that TL and the lenth of PO of lavae exposured in different pH conditionswere significantly differed from that of cultured in natural seawater, however, no significantly differences were found in the length of body rod between natural seawater group and acifiedseawater.4、The results of scanning electron microscopy(SEM) showed that the both surface andcross-section of spicules in S. intermedius larvae cultured in natural seawater are smooth,uniform and compacted. However, we found crossion in both surface and cross-section ofspicules in S. intermedius larvae in seawater bubbled with different concentration of CO2All in all, this study will enrich our knowledge of the potential threats of ocean acidificationon early development of marine organisms in the future, add more evidences to the pool ofmarine species’ vulnerability to progressive ocean acidification, and as well might provide usmore clues to find strategies for sustainable development of marine commercial industry innear-future climate change.