Multivariate analysis of reef community structure in the Belize Barrier Reef complex

The Belize barrier reef complex includes approximately 250 km of barrier reef and three off-shelf atolls up to 40 km east of the barrier reef. Multivariate analysis techniques are being tested for their ability to discriminate patterns of geographical zonation in reef community structure. A stratified, haphazard video-based monitoring scheme has been established at 17 windward fore-reef sites. This preliminary community classification and ordination provides a baseline description of reef communities and indicates a significant difference (1) between atoll versus barrier reef sites, and (2) between southern, northern and central barrier reef sites, despite a relatively high degree of similarity. Two pairs of sites indicate there are significant differences in community structure between 'impacted' and 'non-impacted' sites. In addition, the key taxa responsible for these differences (based on the Bray-Curtis similarity matrix) were identified and include Agaricia tenuifolia and macro algae. Most previous studies have examined stony coral species in such analyses. Because non-coral biota are normally the major community components on Caribbean reefs, they should be included in multivariate analyses of reef communities. Reanalysis of these data using either major benthic substrate categories or only stony coral species produces less discriminating results and illustrates the importance of using a community approach with as much taxonomic detail as possible. Understanding the underlying similarities and differences in biological communities throughout this large reef area is the first step towards the goal of linking these patterns to environmental and management-linked influences.