A coral reef is like a bustling city in an alien world—built not of concrete and steel, but of tiny, living creatures. As corals grow into large colonies, their hard skeletons create an intricate maze of shelters, feeding grounds, and breeding spaces for countless organisms. Coral reefs cover less than 1% of the ocean but support over 25% of all life in it—the highest biodiversity of any ecosystem on the planet. Photo: Noemi Merz/Ocean Image Bank Off the eastern coast of Mauritius, one such thriving underwater metropolis teemed with l...