Back-reef Slope Research Articles

Patterns in the distribution of the crinoid community at Davies Reef on the central Great Barrier Reef

The crinoid community of Davies Reef, a midshelf reef in the central Great Barrier Reef, was systematically sampled in all major crinoid habitats. A total of 294 individuals of 27 species-level taxa was found in 25 sites across the reef. Of these 27 taxa, 20 were confidently assigned to known species. The 25 sitesx27 taxa matrix was subjected to an array of pattern extraction and diagnostic techniques — numerical classification, ordination and minimum spanning trees — to elucidate the structure of the community. These analyses revealed a consistent structure characterized by a species-rich ensemble around the periphery of the reef which was attenuated towards the inside of the reef. This structure contrasts strongly with the patterns seen in other major reef communities, such as hard and soft corals, fish or sponges. In these communities, different parts of the reef are characterized by distinctive sets of species, a depthbased zonation of the communities is evident, and the fore-reef slope typically supports a different ensemble from the back-reef slope. We conclude that the crinoid community offers a significant opportunity to observe the coral reef ecosystem from a different perspective.

Bathymetric Distribution of Foraminifera in Jamaican Reef Environments: ABSTRACT

Recent foraminifera inhabiting Jamaican north-coast fringing reefs display variations in distributional patterns that are related to bathymetry and reef morphology. Sediment samples containing foraminifera were collected along a profile that traversed the back reef (depth 1-2 m), fore-reef terrace (3-15 m), fore-reef escarpment (15-27 m), fore-reef slope (30-55 m), and upper deep fore reef (70 m). Approximately 150 species distributed among 80 genera were identified from the samples. Preliminary analyses indicate that diversity values (S, H^prime) are lowest on the fore-reef terrace (79, 3.0, respectively), increase similarly in back-reef and fore-reef escarpment and slope settings (93, 3.4), and are highest on the deep fore reef (109, 3.7). Larger groupings (suborders) e hibit distinct bathymetric trends with miliolids occurring more commonly in back-reef (comprising 51% of the fauna) than in fore-reef (28%) zones, whereas agglutinated and planktonic species occur more commonly in deeper reef (> 15 m, 9% and 4%, respectively) than in shallower reef zones ( End_of_Article - Last_Page 283------------