Meeting Abstract
Marine mollusks depend on their heavily calcified shells as body armor against a range of predators, including the formidable smashing mantis shrimp. While it has been established for multiple species of mollusks that ocean acidification-like conditions reduce calcification, it is not known how this change in mineralization manifests in the mechanical integrity of their body armor in the context of predation attempts. We hypothesized that changes in calcification in response to medium-term exposure to reduced pH conditions will be sufficient to alter the material properties of the shell in ways that reduce its impact resistance. We tested this hypothesis on two California mollusk species, the mussel Mytilus edulis and the periwinkle Littorina planaxis, that are common prey of the mantis shrimp Hemisquilla californienses. A total of 64 small individuals of each species (Mytilus: 47.4±3.1mm, Littorina: 9.2±0.7mm) were exposed to ambient (pH = 8.2) and reduced pH (stable 7.9, 7.6, fluctuating: 7.9±0.05) conditions for 10 weeks, after which shell growth was documented and shell hardness and stiffness were determined using nanoindentation. The experimental conditions were sufficient to induce significantly lower growth rates in the reduced pH treatments compared to the ambient control group. Mineralization is yet to be analyzed, but our nanoindentation measurements suggest that there is no effect of pH on shell hardness and stiffness in M. edulis and L. planaxis. Thus, for small molluscs, exposure to ocean acidification conditions may not cause changes sufficient to alter the function of their calcified armor.
