Introduction

Background and Rational

The Florida Keys Reef Tract is the third largest coral barrier reef system in the world, extending approximately 270 km along the southeastern coast of the Florida Keys. This system of over six thousand reefs has suffered devastating degradation and destruction over the past few decades due to ocean warming, acidification, and oxygen loss, as well as anthropogenic stressors including overexploitation and pollution. These precious reef environments provide invaluable ecosystem services, from facilitating biodiversity hotspots to enhancing local fisheries production. Preservation and restoration of these habitats is critical, however management strategies can be costly and ineffective.

To maximize restoration success, the roles of reef fishes should be considered when selecting sites for restoration initiatives. They provide coral reefs with an influx of essential nutrients as they migrate from nutrient-rich nursery habitats, such as mangrove forests and seagrass beds. Additionally, herbivorous groups combat macroalgae cover, which hinders coral settlement and growth if left unchecked.

Img 2: Parrotfishes grazing macro algae off corals (left). Other reef fish (right).

Img 1: Comparison between a living coral reef and a dead coral reef.

Research Objectives

First, relationships between species richness, Simpson's diversity index, and continuous environmental predictors (water depth, visibility, temperature, salinity, and dissolved oxygen) will be explored
using scatter plots; relationships between species richness, Simpson's diversity index, and categorical environmental predictors (habitat type, subregion) will be explored using boxplots.

Main objectives:

Use K-means clustering to group sampling sites based on the continuous environmental predictors.
Perform gradient analysis to determine associations between species occurrence, habitat type, and environmental conditions.
Predict habitat type from species occurrence using randomForest to identify sites with atypical reef fish communities. Pair these results with Simpson's diversity index to produce a map of reefs potentially at risk.

Understanding the relationships between species occurrences and environmental factors can help practitioners select sites for coral reef restoration. Sites could be selected such that they are suitable environmentally for reef fishes, helping to attract and retain a rich and diverse array of helpful fish species on newly restored reefs. Gradient analysis will provide further insights into associations between species occurrences, habitat type, and environmental conditions, and can reveal species-specific information as well as general trends. Identifying reefs at risk, defined here as sites with atypical reef fish communities and low diversity, could help focus monitoring and management efforts on these priority locations.