Seawater carbonate chemistry and processes during experiments with seaurchins Hemicentrotus pulcherrimus and Echinometra mathaei, 2004@en

Increased carbon dioxide (CO2) concentration in the atmosphere will change the balance of the components of carbonate chemistry and reduce the pH at the ocean surface. Here, we report the effects of increased CO2 concentration on the early development of the sea urchins Hemicentrotus pulcherrimus and Echinometra mathaei. We examined the fertilization, early cleavage, and pluteus larval stage to evaluate the impact of elevated CO2 concentration on fertilization rate, cleavage rate, developmental speed, and pluteus larval morphology. Furthermore, we compared the effects of CO2 and HCl at the same pH in an attempt to elucidate any differences between the two. We found that fertilization rate, cleavage rate, developmental speed, and pluteus larval size all tended to decrease with increasing CO2 concentration. Furthermore, CO2-seawater had a more severe effect than HCl-seawater on the fertilization rate. By contrast, the effects on cleavage rate, developmental speed, and pluteus larval morphology were similar for CO2- and HCl-seawater. Our results suggest that both decreased pH and altered carbonate chemistry affect the early development and life history of marine animals, implying that increased seawater CO2 concentration will seriously alter marine ecosystems. The effects of CO2 itself on marine organisms therefore requires further clarification.大气中二氧化碳（CO₂）浓度升高会改变碳酸盐化学（carbonate chemistry）组分的平衡，并降低海洋表层海水的pH值。本研究探讨了CO₂浓度升高对两种海胆——刻肋海胆（Hemicentrotus pulcherrimus）与马氏长海胆（Echinometra mathaei）——早期发育的影响。我们通过观测受精、早期卵裂及长腕幼虫（pluteus larval stage）三个发育阶段，评估了CO₂浓度升高对海胆受精率、卵裂速率、发育速度以及长腕幼虫形态的影响。此外，本研究设置了相同pH条件下的CO₂酸化海水与HCl酸化海水对照，以阐明二者对海胆早期发育的影响差异。结果显示，随着CO₂浓度升高，海胆的受精率、卵裂速率、发育速度以及长腕幼虫体长均呈现下降趋势。进一步分析发现，CO₂酸化海水对海胆受精率的抑制作用显著强于HCl酸化海水；而二者对卵裂速率、发育速度以及长腕幼虫形态的影响则无显著差异。本研究结果表明，海水pH降低与碳酸盐化学组分改变均会对海洋动物的早期发育与生活史产生影响，这意味着海水CO₂浓度升高将严重扰动海洋生态系统。因此，CO₂本身对海洋生物的具体作用机制仍需进一步阐明。