Ocean acidification alters properties of the exoskeleton in adult Tanner crabs, <i>Chionoecetes bairdi</i>

ABSTRACT Ocean acidification can affect the ability of calcifying organisms to build and maintain mineralized tissue. In decapod crustaceans, exoskeleton is a multilayered structure composed chitin, protein mineral, predominately magnesian calcite or amorphous calcium carbonate (ACC). We investigated effects on mature (post-terminal-molt) female southern Tanner crabs, Chionoecetes bairdi. Crabs were exposed one three pH levels – 8.1, 7.8 7.5 for 2 years. Reduced led suite body region-specific exoskeleton. Microhardness claw was 38% lower in crabs at compared with those but carapace microhardness unaffected by pH. contrast, reduced altered elemental content (reduced calcium, increased magnesium), not claw. Diminished structural integrity thinning observed both regions; internal erosion present most 7.5, claws these showed substantial external erosion, tooth-like denticles nearly completely worn away. Using infrared spectroscopy, we shift phase crabs: mix ACC found whereas bulk had transformed crabs. With limited capacity repair, long-lived that undergo terminal molt, such as C. bairdi, may be especially susceptible ocean acidification.