Explaining island-wide patterns of Caribbean fish diversity: a multi-scale seascape ecology approach

Geographical patterns of fish diversity across coral reef ecosystems are complex because they are driven by interacting environmental variables operating at multiple spatial scales. In the Caribbean Sea, stressors resulting from human activities have resulted in declines in fish diversity on many coral reefs making the understanding of environmental correlates for fish diversity patterns a priority in marine conservation. To examine environmental correlates of the geographical patterns in fish diversity, where each species responds to the environment differently, and at different spatial scales, we applied a multi-scale seascape approach derived from landscape ecology. Seascape heterogeneity was quantified within patches of coral reef where fish assemblages were surveyed, as well as the surrounding seascape structure (i.e., terrain complexity, patch-mosaic composition, patch proximity and wave exposure) in the nearshore waters of St. John, United States Virgin Islands. Nonparametric statistical learning techniques using single classification and regression trees (CART) and ensembles of boosted regression trees (TreeNet) were used to: 1.) model interactions; and 2.) identify the most influential environmental predictors from multiple data types (diver surveys, terrain models, habitat maps) and spatial scales (1 m2 to 196,350 m2). Classifying the continuous response variables into a binary category and predicting the presence and absence of a fish richness hotspot (top 10%) increased the predictive performance of the models. The best CART model predicted fish richness hotspots with 80% accuracy. The abundance of living scleractinian coral measured within 1 m2 quadrats and the topographic complexity of the surrounding seafloor terrain (150 m radius) interacted to explain geographical patterns in fish richness hotspots. The poor performance in predicting continuous variability in fish diversity could be due to a process of homogenisation occurring as reefs degrade which reduces the variability in diversity at the island-scale and decouples the diversity-environment relationship.

ISCED Categories

The highlighted icons, represent the fields of education (in compliance with ISCED Classification) engaged during this course/programme.

0511 - Biology", "0521 - Ecology