Spatial patterns and ecology of benthic communities on a high-latitude South Florida (Broward County, USA) reef system

High-latitude reef communities consisting of typical Caribbean fauna of variable composition and density exist on four parallel ridges at varying depths along the Broward County (Florida, USA) coast. Two of these ridges, at 7-13 and 15-30 m in depth, are drowned early Holocene coral reefs of 5 and 7 ky uncorrected radiocarbon age. In this study, community data were collected on each reef using 50-m, line-intercept transects. Using multivariate non-metric statistics, the data show distinct differences in benthic community structure across several spatial gradients. Diversity indices revealed that while all values were low, species diversity (H') was consistent throughout the county, and species richness (d) and evenness (J') increased along a north-south gradient. Scleractinian coral (27 species) cover was low (