Additive influence of extreme events and local stressors on coral diversity in the Mesoamerican Reef during the last decade

Abstract Losing coral diversity is one of the most important consequences of coral reefs' ongoing degradation. Alternate: As the planet enters its sixth global extinction event, the loss of biodiversity due to coral reef degradation becomes of paramount importance. However, the loss of coral species diversity and its relationship to multiple global and local stressors remains largely untested on different temporal or spatial scales. This study evaluates the change in coral species diversity and its relationship to different stressors and habitat characteristics, using ecological data from 73 sites in the Mesoamerican Reef (MAR) and a variety of potential explanatory variables derived from remote sensing. We found a loss of coral diversity in the period analyzed, from 2010 to 2018. In addition to a decrease in diversity, there was also a considerable change in coral assemblages. The coral reefs that presented a greater loss of species were those with higher initial diversity and those with a higher number of annual bleaching risk events. Surprisingly, coral reefs exposed to hurricanes and turbidity with intermediate magnitude did not experience the same loss in diversity; some reefs even experience an increased diversity in this timeframe. The rate of increase in macroalgal cover was related to the decrease in coral diversity. Our results highlight the need to protect reefs with high diversity and constantly exposed to high heat stress events. These reefs should be considered sites of relevance in future conservation plans in the current context of global environmental change.