Coral Reef Health Indices <i>versus</i> the Biological, Ecological and Functional Diversity of Fish and Coral Assemblages in the Caribbean Sea

This study evaluated the relationship between the indices known as the Reef Health Index (RHI) and two-dimensional Coral Health Index (2D-CHI) and different representative metrics of biological, ecological and functional diversity of fish and corals in 101 reef sites located across seven zones in the western Caribbean Sea. Species richness and average taxonomic distinctness were used to asses biological estimation; while ecological diversity was evaluated with the indices of Shannon diversity and Pielou´s evenness, as well as by taxonomic diversity and distinctness. Functional diversity considered the number of functional groups, the Shannon diversity and the functional Pielou´s evenness. According to the RHI, 57.15% of the zones were classified as presenting a "poor" health grade, while 42.85% were in "critical" grade. Based on the 2D-CHI, 28.5% of the zones were in "degraded" condition and 71.5% were "very degraded". Differences in fish and coral diversity among sites and zones were demonstrated using permutational ANOVAs. Differences between the two health indices (RHI and 2D-CHI) and some indices of biological, ecological and functional diversity of fish and corals were observed; however, only the RHI showed a correlation between the health grades and the species and functional group richness of fish at the scale of sites, and with the species and functional group richness and Shannon diversity of the fish assemblages at the scale of zones. None of the health indices were related to the metrics analyzed for the coral diversity. In general, our study suggests that the estimation of health indices should be complemented with classic community indices, or should at least include diversity indices of fish and corals, in order to improve the accuracy of the estimated health status of coral reefs in the western Caribbean Sea.本研究针对加勒比海西部七个区域内的101个珊瑚礁点位，评估了珊瑚礁健康指数（Reef Health Index, RHI）与二维珊瑚健康指数（two-dimensional Coral Health Index, 2D-CHI）两类指标，和鱼类、珊瑚的生物、生态及功能多样性的代表性度量之间的关联。研究采用物种丰富度与平均分类学差异度开展生物学评估；生态多样性则通过香农多样性指数、皮卢均匀度指数，以及分类多样性与分类差异度进行测算。功能多样性则涵盖功能群数量、香农多样性指数与功能型皮卢均匀度指数。依据RHI的评定结果，57.15%的区域被归类为“健康状况较差”等级，剩余42.85%处于“危急”等级；基于2D-CHI的结果则显示，28.5%的区域处于“退化”状态，71.5%为“严重退化”。本研究通过置换方差分析（permutational ANOVAs）验证了不同点位与区域间鱼类、珊瑚多样性的差异。同时观察到两类健康指数（RHI与2D-CHI）与部分鱼类、珊瑚的生物、生态及功能多样性指数间存在差异；但仅RHI展现出健康等级与点位尺度下鱼类物种丰富度及功能群丰富度的相关性，以及区域尺度下鱼类群落的物种丰富度、功能群丰富度与香农多样性的相关性。两类健康指数均未与珊瑚多样性的分析度量存在关联。总体而言，本研究表明，为提升加勒比海西部珊瑚礁健康状况评估的准确性，健康指数的测算应当辅以经典群落多样性指数，或至少纳入鱼类与珊瑚的多样性指数，以完善评估体系。