The effects of coral assemblage shift on reef functions in Akumal, Mexico

Abstract

Caribbean coral reefs have suffered shifts in their coral assemblages, driven by local and global stressors. These shifts have affected reef functions, ecosystem processes, and services essential to human well-being. Akumal Reef, located in the northern Mexican Caribbean, generates valuable ecosystem services, mainly linked to tourism, that depend on the persistence of the reef’s physical functionality. In this study, decadal changes in coral assemblages and their effects on functional traits decline were investigated. Coral species cover was systematically monitored at 14 sites along Akumal Reef in 2001, 2010, and 2019. These data were translated to functional traits allowing the classification of coral species into life-history strategies (competitive, stress-tolerant, and more opportunistic ‘weedy’ species). Our results indicate a significant decline in stress-tolerant species cover (mostly from the genus Orbicella) in Akumal Reef between 2001 and 2010 and between 2010 and 2019, with no significant changes in coral cover of other life-history strategies. The significant shifts away from stress-tolerant species during the time studied in Akumal Reef influenced the deterioration of functional traits related to reef physical functionality, such as calcification, rugosity, average maximum colony size, and reef functional index. Currently, Akumal reef sites are dominated by non-framework-building weedy coral species and are mostly below the 10% hard cover estimated threshold for positive reef accretion in the Caribbean. Therefore, management strategies in Akumal Reef should be integrative and oriented towards reducing local stressors while actively restoring the functional structure of coral reefs and maintaining their environmental services.