An international research team led by marine biologist Prof. Dr. Maren Ziegler from Justus Liebig University Giessen (JU) has developed an innovative method for reconstructing the past of corals and their symbiosis with algae by drilling into coral skeletons. The results, published in Global Change Biology, offer new insights into changes in symbiotic single-celled algae species that are crucial to the survival of coral reefs.