A collaborative effort to integrated biological and chemical ocean acidification observations

Ocean acidification (OA) due to the CO₂ emissions from human activities is a serious threat to marine life and the overall health of ecosystems. As OA changes ocean chemistry, it forces marine organisms to spend more energy just to survive in these new and challenging conditions. This stress is especially noticeable in organisms with shells and skeletons. However, the impact likely extends beyond individual species, potentially disrupting entire marine communities and the delicate balance within these ecosystems.

Traditionally, scientists have studied OA through two main approaches: by measuring variations in the ocean's carbonate system and by running controlled lab experiments on biological responses. While these methods have provided valuable insights, they are not enough to capture the complex, real-world impacts of OA on diverse marine environments. One complementary approach is to observe such changes in natural environment over time.

Recognizing the urgency of this issue, IOC-UNESCO has initiated a joint project aimed at creating a comprehensive system for tracking and understanding the biological impacts of OA across various ecosystems. This project, guided by the work of the biological working group of the Global Ocean Acidification Observing Network (GOA-ON) and its publication (Widdicombe et al. 2023¹), seeks to build a strong foundation for assessing OA's global effects by combining chemical and biological observation data, directly supporting global initiatives like SDG 14.3 and the Kunming-Montreal Global Biodiversity Framework.

The project follows a structured, multi-phase approach, beginning with a targeted set of sites with long-term carbonate system data and extensive biological and oceanographic observations. This first phase aims to test the idea that rates of biological and carbonate chemistry changes should correlate. It would also allow to isolate biological responses to OA, identify sensitive biological traits, and conduct causality analyses to detect OA impacts within biological data. The focus is on five key biological and ecological traits — calcification, primary production, growth, biodiversity, and genetic adaptation — that have demonstrated links to OA and provide a foundation for understanding its effects on marine life.

In the second phase, this approach will be applied to additional sites with comprehensive datasets to identify cases where OA may be the primary driver of biological changes. This phase will also explore deviations from expected patterns due to other stressors, such as heatwaves, warming, and nutrient enrichment.

The final phase will analyze sites where only biological data are available, assessing whether OA impacts can be identified in the absence of direct carbonate system measurements. This analysis aims to expand the scope of OA impact assessments by identifying regions where OA potentially influences biological traits and community structures.

Ultimately, this project aims to develop innovative observation strategies that integrate biological and chemical monitoring, contributing to globally applicable best practices for OA impact assessment. This will support informed decision-making and help shape adaptation and mitigation strategies essential for safeguarding marine ecosystems.

¹Widdicombe et al. 2023, DOI: 10.5194/os-19-101-2023