Pteropods as indicators for Cumulative Ocean Acidification Exposure

Pteropods are ubiquitously distributed pelagic marine zooplankton of importance in productive upwelling regimes, where they represent an important prey item for variety of economically, ecologically, and culturally important fish species. Because of their extreme sensitivity to ocean acidification conditions, pteropods can be used to establish cause and effect relationships between OA status and biological condition. Incorporating biological responses into a successful management framework requires laboratory studies that demonstrate sentinel organism responses to specific stressors, while also documenting population or community level effects in the field linked to that stressor. Here, we describe the state of the science and an approach that demonstrates the linkage necessary to use pteropods as a sentinel organism for resource management under conditions of ocean acidification. To demonstrate this utility, newly developed methods were used to determine and quantify pteropod responses in the natural environment. Responses such as shell dissolution, shell calcification, changes in vertical distribution, and survival success were assessed to establish pteropod condition under a variety of OA conditions. While no single species or set of species can adequately capture all aspects of ecosystem change, pteropods represent first quantifiable, specific indicators for ocean acidification’s effects on marine systems. The approach can be used in water quality assessments and in living marine resource management as part of the rapid and cost-effective monitoring of biological responses to ocean acidification. The social challenges of changing ocean chemistry will continue to grow in coming decades, making the availability of such straightforward metrics of impact indispensable across scales of time and space of relevance to managers.