From coral skeletons to autonomous sensors: monitoring ocean acidification

Ocean acidification, the progressive reduction in seawater pH caused by rising atmospheric CO₂, represents one of the most pressing threats to marine ecosystems. By altering the carbonate chemistry of the ocean, it compromises the ability of calcifying organisms, such as corals, shellfish, and some plankton, to build and maintain skeletons and shells, with cascading effects on biodiversity, fisheries, and coastal communities. Understanding and monitoring these changes is essential to predict impacts, guide mitigation strategies, and support resilient management of marine resources.

This talk explored different methods of ocean acidification monitoring, highlighting approaches from historical reconstructions to cutting-edge autonomous sensing. Paleo proxies, such as the chemical composition of coral skeletons, allow us to reconstruct long-term trends in pH, providing context for current changes and identifying natural variability over centuries. Building on these foundations, in situ measurements using traditional shipboard sampling have offered high-accuracy snapshots of carbonate chemistry, but remain limited in temporal and spatial coverage.

Recent advances in autonomous sensing now allow continuous, high-resolution monitoring of Essential Ocean Variables across a range of ecosystems from shallow coral reefs to the deep open ocean. Lab-on-chip sensors, capable of measuring pH, alkalinity, and other key parameters, provide unprecedented insights into the dynamics of marine carbonate chemistry under natural and anthropogenic stressors. These technologies have been deployed across several platforms, including research vessels and moorings, revealing how biogeochemical processes respond to environmental variability.

The talk also highlighted the practical application of these tools through capacity-building efforts in Small Island Developing States. By providing monitoring kits and training local stakeholders, these programmes support locally-driven data collection, enhancing understanding of ocean acidification in regions highly vulnerable to climate change. Partnerships with industry have further enabled the translation of research into operational tools for sustainable marine management. Bringing these approaches together highlights both what we understand about ocean acidification and where improved observations are still needed. The talk concluded with reflections on the progress made so far and the opportunities that new tools and partnerships provide for expanding future monitoring efforts.

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