Ocean Acidification (OA) owing to increasing atmospheric CO2 may have profound impacts on marine ecosystems including coral reefs that may lose their fundamental function of reef construction. However, large spatial-temporal variation and technological hurdles of monitoring seawater carbonate chemistry prohibit accurate predictions of OA impacts on coral reefs, and thus, effective mitigation and adaptation strategies. Here, we propose to first establish an innovative methodology for monitoring of OA, replicable across the world. The authors of this proposal are the inventors of the core technology. As a second step, we propose to monitor and model seawater carbonate chemistry (pH-alkalinity) and reef calcification capacity in five sites (Okinawa, Hawaii, Réunion, Mayotte Islands, and Tonga). Other good practices in OA management will be evaluated for cross-learning between the five sites. One example we are aiming to evaluate is seaweed farming to absorb CO2 and promote coral growth. Fisheries in Onna-son village in Okinawa, Japan have been culturing corals and seaweed simultaneously for decades with empirical knowledge that they stimulate mutual growth, but with no knowledge of the underlying mechanism. By providing scientific evidence, this "Onna-son model" may be of potential interest in other sites. The final objective of this consortium is to construct a "toolbox" consisting of tools such as methodology and good practices in science, technology, socio-economic models, climate change adaptation/mitigation, and policy aimed at ameliorating negative impacts of OA in coral reefs. We aim to maintain close communication with local and national stakeholders as well as international organizations throughout the project. We will conduct outreach, education and training efforts at both local and international events. Data management will be conducted in line with the Belmont Forum Open Data Policy and Principles. Special attention will be paid to the gender dimensions of the project.