Global warming decreases connectivity among coral populations

Global warming is killing corals; however, the effects of warming on population connectivity, a process fundamental to reef recovery, are largely unexplored. Using a high-resolution (as high as 200 m), empirically calibrated biophysical model of coral larval dispersal for the southern Great Barrier Reef, we show that the increased larval mortality and reduced competency duration under a 2 degrees C warming alter dispersal patterns, whereas projected changes in large-scale currents have limited effects. Overall, there was on average a 7% decrease in the distance larvae disperse (among-reef interquartile range (IQR), -10% to -4%), an 8% decrease in the number of connections into each reef (IQR, -11% to -3%) and a 20% increase in local retention (IQR, 0% to +49%). Collectively, these shifts imply that 2 degrees C of warming will reduce inter-reef connectivity, hampering recovery after disturbances and reducing the spread of warm-adapted genes. Such changes make protections more effective locally, but may require reducing spacing between protected areas. The authors develop a high-resolution model of coral larval dispersal for the southern Great Barrier Reef. They show that 2 degrees C of warming decreases larval dispersal distance and connectivity of reefs, hampering post-disturbance recovery and the potential spread of warm-adapted genes.

Automated summary

The study demonstrates that a 2-degree Celsius warming will reduce the dispersal distance of coral larvae and connectivity between reefs, impacting coral reef recovery and the spread of warm-adapted genes.