The potential of ocean acidifi cation on suppressing larval development in the Pacifi c oyster Crassostrea gigas and blood cockle Arca infl ata Reeve

We evaluated the effect of pH on larval development in larval Pacific oyster (Crassostrea gigas) and blood cockle ( Arca inflata Reeve). The larvae were reared at pH 8.2 (control), 7.9, 7.6, or 7.3 beginning 30 min or 24 h post fertilization. Exposure to lower pH during early embryonic development inhibited larval shell formation in both species. Compared with the control, larvae took longer to reach the D-veliger stage when reared under pH 7.6 and 7.3. Exposure to lower pH immediately after fertilization resulted in significantly delayed shell formation in the Pacific oyster larvae at pH 7.3 and blood cockle larvae at pH 7.6 and 7.3. However, when exposure was delayed until 24 h post fertilization, shell formation was only inhibited in blood cockle larvae reared at pH 7.3. Thus, the early embryonic stages were more sensitive to acidified conditions. Our results suggest that ocean acidification will have an adverse effect on embryonic development in bivalves. Although the effects appear subtle, they may accumulate and lead to subsequent issues during later larval development.

本研究探究了pH值对太平洋牡蛎（Pacific oyster, *Crassostrea gigas*）及血蚶（blood cockle, *Arca inflata Reeve*）幼体发育的影响。实验于幼体受精后30分钟或24小时启动，将受试幼体分别置于pH 8.2（对照组）、7.9、7.6及7.3的水体环境中培育。在早期胚胎发育阶段暴露于低pH环境，会抑制两种受试生物的幼虫贝壳形成。与对照组相比，在pH 7.6和7.3环境中培育的幼体，达到D形幼虫（D-veliger）阶段所需的时间更长。若幼体在受精后即刻暴露于低pH环境，则pH 7.3组的太平洋牡蛎幼体，以及pH 7.6和7.3组的血蚶幼体的贝壳形成会显著延迟。但若将酸化暴露的起始时间推迟至受精后24小时，则仅pH 7.3组的血蚶幼体的贝壳形成受到抑制。由此可见，早期胚胎阶段对酸化环境的敏感性更高。本研究结果表明，海洋酸化会对双壳类（bivalves）的胚胎发育产生不利影响。尽管此类影响看似微弱，但可能会逐步累积，并在后续的幼虫发育阶段引发各类问题。