Extraction of a coral core in Thailand | Photo: Yvonne Sawall, ZMT

„Witnesses to the Climate Emergency: Ocean acidification crisis and global warming observations from tropical corals (OASIS)“

Our oceans absorb massive amounts of the greenhouse gas CO2 from the Earth's atmosphere. When excess CO2 reacts with seawater, carbonic acid is formed and the pH of the seawater decreases. This process, known as ocean acidification (OA), has consequences for calcifying organisms such as corals to fully build their functional skeletons.

Project OASIS will investigate the development of OA because scientific knowledge on the effects of OA in the tropics has so far been very limited due to the lack of long-term pH measurements and proxy reconstructions in the tropical oceans.

By analysing boron isotopes in long-lived corals, Wu will determine the pH values of seawater in various geographical regions of the Atlantic, Pacific and Indian Oceans. Boron is a natural component of seawater and its isotopes are sensitive to changes in ocean pH. Corals take in this seawater to form their calcareous skeleton. Thus, any change in pH can be detected in the boron isotopes incorporated in the coral skeleton.

By determining the pH over the most recent few hundred years, Wu will reconstruct the global development of OA and rates of pH change as well as the carbonate content of our tropical oceans before and after the Industrial Revolution. These results will provide valuable data to understand the levels of CO2 penetrating into the oceans and draw conclusions on the changing climate parameters.

The project results can provide sound information for policymakers and stakeholders who are committed to mitigating the increase in atmospheric CO2 and its negative consequences.

The OASIS project is funded by the Federal Ministry of Education and Research (BMBF) under the "Make our Planet Great Again – German Research Initiative", grant number 57429626, implemented by the German Academic Exchange Service (DAAD).


Project Partner (Germany)


International Project Partners

Centre for Marine Environmental Sciences at the University of Bremen (MARUM), Bremen


Lamont-Doherty Earth Observatory (LDEO), Palisades, New York (USA)

IRD France Nord, Paris (France)

IRD Centre Noumea (New Caldeonia)

Scripps Institution of Oceanography, San Diego, California (USA)

Indiana State University, Terre Haute, Indiana (USA)

University of Puerto Rico, Mayagüez (Puerto Rico)