Ancient reef-building corals had a little help from microbial friends

Nitrogen-isotope analysis provides geochemical evidence that, similar to modern corals, some extinct coral groups had a symbiotic association with photosynthetic microorganisms. This ‘photosymbiosis’ might have contributed to the high productivity of ancient reefs in low-nutrient environments and puts long-term ecological research on ancient reefs into a fresh perspective. Palaeozoic corals formed symbiotic relationships with photosynthetic microorganisms.