Shell dissolution rates differ fourfold between mussel species

Marine mussels display differential habitat preferences, with species like Mytilus californianus favoring fully saline environments and Mytilus trossulus inhabiting sites with greater freshwater input. Determining abiotic dissolution rates of these species under ocean acidification is essential for predicting future consequences of climate change for coastal populations. We examined shell dissolution rates of these congeners under a range of pH (6.5-9.3) and aragonite saturation states (0.1-9.0). We additionally quantified experimentally the relative importance of dissolution from interior versus exterior shell surfaces. M. trossulus exhibited 4x higher shell dissolution rates than M. californianus. When the shell interior was sealed against seawater exposure, dissolution rates decreased significantly in both species, indicating high abiotic dissolution on the shell interior. Results demonstrate that dissolution rates can vary between congeners inhabiting the same biogeographic region. Our finding that freshwater-tolerant M. trossulus has higher abiotic dissolution under ocean acidification is important because low salinity may further retard calcification, altering future intertidal population structure along freshwater-influenced coastlines.

海洋贻贝展现出差异化的栖息地偏好，如加州贻贝 (Mytilus californianus) 偏好全盐度环境，而紫贻贝 (Mytilus trossulus) 则栖息于淡水输入量更高的区域。明确这两个物种在海洋酸化 (ocean acidification) 条件下的非生物溶解速率，对于预测气候变化对沿海种群的未来影响至关重要。我们针对这两种同属贻贝，在pH值范围6.5~9.3以及文石饱和度 (aragonite saturation states) 范围0.1~9.0的实验条件下，测定了其贝壳溶解速率；此外，我们通过实验量化了贝壳内表面与外表面溶解的相对重要性。实验结果显示，紫贻贝的贝壳溶解速率是加州贻贝的4倍。当将贝壳内表面密封以隔绝海水接触时，两种贻贝的溶解速率均显著下降，表明贝壳内表面存在较高的非生物溶解作用。研究结果表明，栖息于同一生物地理区域的同属物种，其贝壳溶解速率可存在差异。我们的研究发现，耐淡水的紫贻贝在海洋酸化条件下具有更高的非生物溶解速率，这一发现具有重要意义：低盐度环境可能进一步延缓钙化作用，进而改变受淡水影响的海岸线沿线未来的潮间带种群结构。