The reorganization of reef communities following the end-Permian mass extinction

The transition from Permian to Triassic time, amidst the largest extinction in the history of life, is characterized by the loss of metazoan reefs followed by a protracted and total reorganization of reef ecosystems. This restructuring of reefs, was permanent, and involved a succession from the Permian reef optimum to their total demise, followed by a long-term absence of metazoan reefs in the Early Triassic and then ultimately a delayed recovery in the Middle Triassic. During the end-Permian mass extinction, reef building metazoans suffered a major extinction that resulted in a severe drop in reef skeletal carbonate production by >99%. Following the extinction, microbial reefs that formed without metazoans took over for 5-6 Myr during the entire Early Triassic. This microbial reef resurgence has been widely studied and is thought to represent long-term environmental stress related to the end-Permian mass extinction that Suppressed the recovery of metazoans while simultaneously fostering microbialite development. In the Middle Triassic, metazoans reef's became re-established, although pre-extinction biodiversity values were not attained until the Late Triassic.