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.

火山二氧化碳喷口（Volcanic CO2 vents）是研究海洋生物对海洋环境变化（海洋酸化，Ocean Acidification, OA）的生物响应的极具价值的研究环境。海洋有壳软体动物对海水碳酸盐化学的变化极为敏感。本研究以大西洋东北部加那利群岛拉帕尔马岛周边的火山二氧化碳喷口为研究位点，该区域在潮汐周期内存在自然pH梯度，范围为7.0至8.2，以此探究pH降低对潮间带腹足类物种Phorcus sauciatus的影响。研究对对照位点与喷口位点的种群密度、个体大小频率分布、贝壳形态、贝壳完整性、抗断裂性能及抗干燥能力进行了评估。结果显示，在该pH梯度范围内，pH降低未对种群参数或抗干燥能力产生显著影响，但贝壳形态、贝壳完整性与抗断裂性能存在显著差异。相较于对照位点的个体，喷口位点的个体具有更高的贝壳长宽比、更严重的贝壳溶蚀与破损比例，且贝壳强度受损。本研究结果表明，长期暴露于高二氧化碳分压（pCO2）环境会对P. sauciatus的贝壳特性产生负面影响，但对种群表现无显著影响。此外，本研究推测贝壳特性的丧失可能会改变捕食者与猎物间的相互作用。