Ancient reefs are widely acknowledged as crucial ecosystems for understanding the development of marine biodiversity and the stability of marine ecosystems in deep time. They offer insights into how reef systems are influenced by shifts in environmental conditions and provide valuable information for predicting ecological crises and conserving present-day marine organisms.

Although fossil reefs were built by various organisms, they exhibit remarkable similarities to modern counterparts in terms of structure and environmental context. The Palaeozoic Era witnessed the transition from microbial to metazoan reefs as metazoans emerged from the Cambrian to the Early Ordovician, and shifts from metazoan to microbial reefs during mass extinction events. These shifts in reef-building communities were accompanied by episodic declines and increases in shallow marine benthic microbial carbonate sediments throughout the Phanerozoic. Periods of higher microbial carbonate abundance often corresponded with lower invertebrate and reef diversity, suggesting a complex interplay between these organisms in shaping reef ecosystems over deep time. Furthermore, the Palaeozoic Era boasts a diverse array of reef builders, whose contributions remain incompletely understood despite their role in shaping reef structures comparable to modern developments.

This session aims to explore the co-evolution of Palaeozoic reefs and environmental changes, with a particular emphasis on the involvement of microorganisms in sedimentary processes, biomineralization, and their contributions to carbon neutrality and the evolution of a habitable Earth. By delving into these topics, the session will provide insights into the long-term preservation of modern reef habitats amidst increasing global warming and anthropogenic impacts.