On an expedition with the research vessel POSEIDON and the submersible JAGO, marine biologists from GEOMAR collected corals at Trondheim Fjord (Norway) for their investigations. “During our JAGO dives, we examined the condition of the reefs. We documented their expansion and the diverse community living in the reefs and carefully chose our samples,” explains Janina Büscher. The PhD student from the department of Biological Oceanography at GEOMAR conducted the experiments and is lead author of a publication on the effects and impact of ocean acidification and warming on the growth and fitness of Lophelia pertusa in the research journal Frontiers in Marine Science. “The richness in species of these reefs that exist in almost complete darkness and at temperatures below ten degrees Celsius is very impressive.” Many of these underwater oases, grown over centuries, are protected as natural heritages. Their diversity ensures the resilience of the fjord ecosystem, and many species of fish find shelter and food in the reefs.