Seawater carbonate chemistry and density and size-frequency distribution, shell morphology, shell integrity, fracture resistance, and desiccation tolerance of intertidal gastropod

Volcanic CO2 vents are useful environments for investigating the biological responses of marine organisms to changing ocean conditions (Ocean acidification, OA). Marine shelled molluscs are highly sensitive to changes in seawater carbonate chemistry. In this study, we investigated the effects of reduced pH on the intertidal gastropod, Phorcus sauciatus, in a volcanic CO2 vent off La Palma Island (Canary Islands, North East Atlantic Ocean), a location with a natural pH gradient ranging from 7.0 to 8.2 over the tidal cycles. Density and size-frequency distribution, shell morphology, shell integrity, fracture resistance, and desiccation tolerance were evaluated between populations from control and CO2 vent sites. We found no effects of reduced pH on population parameters or desiccation tolerance across the pH gradient, but significant differences in shell morphology, shell integrity, and fracture resistance were detected. Individuals from the CO2 vent site exhibited a higher shell aspect ratio, greater percentages of shell dissolution and break, and compromised shell strength than those from the control site. Our results highlight that long-term exposure to high pCO2 can negatively affect the shell features of P. sauciatus but may not have a significant effect on population performance. Moreover, we suggest that loss of shell properties could lead to changes in predator-prey interactions.

火山CO₂喷口是探究海洋生物响应海洋环境变化（海洋酸化，Ocean Acidification, OA）的理想研究场所。海洋带壳软体动物对海水碳酸盐化学环境的变化极为敏感。本研究以东北大西洋加那利群岛拉帕尔马岛近海的一处火山CO₂喷口区域为研究位点，该区域在潮汐周期内存在自然pH梯度（范围7.0至8.2），并以此探究pH降低对潮间带腹足类物种锈凹螺（Phorcus sauciatus）的影响。本研究对对照位点与CO₂喷口位点的该物种种群的密度、尺寸频率分布、贝壳形态、贝壳完整性、抗断裂性能以及耐旱性进行了评估。研究结果显示，在整个pH梯度范围内，pH降低对种群参数与耐旱性均无显著影响，但贝壳形态、贝壳完整性及抗断裂性能存在显著差异。相较于对照位点的个体，CO₂喷口位点的个体贝壳长宽比更高，贝壳溶解与破损比例更大，且贝壳强度受损。本研究结果表明，长期暴露于高pCO₂环境会对锈凹螺的贝壳性状产生负面影响，但对种群生存表现无显著影响。此外，本研究推测贝壳性状的丧失可能会改变捕食者与猎物之间的相互作用关系。