They are the archives of the oceans. Corals are a great indicator of how much human activities affect our oceans. Funded by the Franco-German fellowship program “Make Our Planet Great Again,” researchers in the U Bremen Research Alliance are studying the extent of global warming in tropical waters.
The forearm-thick whitish drill core held by Dr. Henry Wu of the Leibniz Centre for Tropical Marine Research (ZMT) has come a long way. It originates from a stony coral from the coastal region off Rotuma, an island in the Republic of Fiji, more than 15,000 kilometers from Bremen. The oldest corals being examined by the paleo-climatologist are more than 100,000 years old. In the course of their lives, they have accumulated a vast amount of information.
Corals grow on average a few millimeters per year. They thrive best in clean water and live up to 50 meters below the surface of the sea, where sunrays can still reach them. Just like the growth rings of trees, the micro samples from their calcareous skeleton tell of changing environmental conditions: temperature fluctuations, the amount of rainfall, ocean acidification, and salinity – and they do so with month-to-month precision.
Wu is using these archives of the ocean within the context of his five-year research project. “Climate has always been changing naturally. We want to know: How profound were these changes? What impact has industrialization had since the beginning of the 19th century?” says the researcher. “If we know the past, we can better predict the future.”