La Nina-like conditions triggered 2500-yr-long Panama coral reef collapse

A new study has revealed that La Nina-like conditions in the Pacific Ocean off the coast of Panama were closely associated with 2,500-year-long abrupt shutdown in coral reef growth.

The research at Georgia Institute of Technology found cooler sea temperatures, greater precipitation and stronger upwelling, all indicators of La Nina-like conditions at the study site in Panama, during a period when coral reef accretion stopped in this region around 4,100 years ago.

Kim Cobb said that investigating the long-term history of reefs and their geochemistry is something that is difficult to do in many places, so this was a unique opportunity to look at the relationship between reef growth and environment. This study shows that there appears to have been environmental triggers for this well-documented reef collapse in Panama.

The new study provides data to assist scientists in understanding how changes in the environment trigger long-term changes in coral reef growth and ecosystem function, which is a critical challenge to coral-reef conservation.

Lead author Lauren Toth said that temperature was a key cause of reef collapse and modern temperatures are now within several degrees of the maximum these reefs experienced over their 6,750 year history and it's possible that anthropogenic climate change may once again be pushing these reefs towards another regional collapse.

Cobb added that they saw evidence for a different climate regime during that time period and the geochemical signals were consistent with a period that is very cool and very wet, with very strong upwelling, which is more like a modern day La Nina event in this part of the Pacific.

Cobb noted that these conditions would have been for quite an extended time, which suggests that the reef was quite sensitive to prolonged change in environmental conditions, so sensitive that it stopped accreting over that period.

Toth added that a broad-scale perspective on long-term reef growth and environmental variability would allow us to better characterize the environmental thresholds leading to reef collapse and the conditions that facilitate survival and a better understanding of the controls on reef development in the past will allow them to make better predictions about which reefs may be most vulnerable to climate change in the future.

The study appears in the journal Nature Climate Change.