Exploring three-dimensionality and heterogeneity: Maldivian coral reefs post-thermal anomalies

Abstract

Increasing anthropogenic pressures and global warming pose severe threats to coral reefs worldwide, leading to the loss of their three-dimensional structure and biodiversity. The rugosity index (RI) has been applied to Maldivian reefs surveyed over time, particularly after the severe thermal anomaly of 2016, to assess the effect of coral mortality on the three-dimensional structure of reefs. RI assessments were conducted on both lagoon and ocean reefs at various depths.

Although the ocean reefs exhibited a greater resilience to the thermal anomaly compared to lagoon reefs, a reduction in three-dimensionality was observed in all reefs after the 2016 bleaching event, regardless of depth. A slight increase of reefs’ heterogeneity was observed in the subsequent years.
RI represents a valuable tool for quickly monitoring the three-dimensionality of coral reefs. Because of the additional information it provides on the reef health, the RI should be integrated with the other commonly adopted ecological indices in tropical reefs monitoring programs.