High vulnerability of ecosystem function and services to diversity loss in Caribbean coral reefs

Determining how ecosystem function and services are related to diversity is necessary for predicting the consequences of diversity loss and for setting goals and priorities for marine conservation. The consequences of biodiversity loss for ecosystem functions and services depend on the level of functional redundancy – the number of species with similar ecological functional traits. Using field data on fish assemblages from 199 coral reef and lagoon sites from six islands, and on local fisheries from four islands in The Bahamas, we examined levels of functional diversity and redundancy within these assemblages and determined how fish biomass and local fisheries catches vary with local diversity. A majority of functional groups contain few species, suggesting that these assemblages have limited functional redundancy. Most also include species targeted by local fisheries, thus fishing has the potential to broadly impact food webs. Comparisons between a large marine reserve and fished reefs confirm that fishing significantly reduces functional redundancy and removes whole functional groups. Positive exponential relationships of fish biomass and fisheries catches with species and functional diversity highlight that even small declines in biodiversity may result in large reductions in secondary production and seafood provision. Taken together, these results indicate that Caribbean fish assemblages have low functional redundancy and high vulnerability of ecosystem functions and services to diversity loss, and that protection of multi-species assemblages is needed to maintain functions and services.