What did ancient reefs with more crustose coralline algae have in common?

Details

Crustose coralline algae (CCA) are key producers of carbonate sediment on reefs today. Despite their importance in modern reef ecosystems, their long-term relationship with reef development had not been quantitatively assessed in the fossil record.

The study analyzed data from 128 Cenozoic coral reefs, collected from the Paleobiology Database, the Paleoreefs Database and original literature. It assessed how CCA abundance correlated with fossil reef framework and taxonomic diversity, including both corals and reef-dwelling organisms.

Chi-squared tests showed a significant correlation between reef type and CCA abundance; post-hoc tests associated greater CCA involvement with stronger reef structure. General linear models also showed that reefs with more CCA had greater diversity of reef-dwelling organisms.

The authors concluded that CCA increased the building capacity, structural integrity and diversity of ancient coral reefs. They interpreted the analyses as showing that CCA functioned similarly on Cenozoic and modern coral reefs, making studies of ancient reef collapse more meaningful as modern analogues.