Vulnerability and Adaptation Strategies of Pteropods in the California Current Ecosystem

The ocean uptake of anthropogenic CO2 has shoaled the aragonite saturation horizon in the California Current Ecosystem, but only a few studies to date have demonstrated widespread biological impacts of ocean acidification under present-day conditions. Pteropods are especially important for their role in carbon flux and energy transfer in pelagic ecosystems. In the California Current Ecosystem, conditions are becoming increasing unfavorable for sustaining shell maintenance because of enhanced dissolution. Our results show a strong positive correlation between the proportion of pteropods with severe dissolution and the percentage of the water column that is undersaturated with respect to aragonite. From this relationship, we are able to determine the extent of dissolution for the pre-industrial era, 2011, and 2050. Our calculations show that dissolution has increased by 30% since the beginning of the industrial era, and could increase to 70% by 2050. Although dissolution is occurring in most of the investigated pteropod species, some species have changed their daily vertical distribution pattern by migrating to upper supersaturated waters to avoid corrosive waters, a potential indication of an adaptation strategy to ocean acidification.