Quantitative habitat mapping and description form the basis for understanding the provisioning of ecosystem services and habitat connectivity, and hence provide an essential underpinning for marine spatial planning, management and conservation. Based on 869 video stations in a 150 x 200 m grid, we mapped 25.3 km2 of the near-shore island shelf of St. Eustatius at depths ranging 5-30 m. This yielded a coarse-grained map of the principal habitat classes of St. Eustatius’ seascapes. A total of nine principal seafloor habitats were distinguished. Gorgonian reefs amounted to 22% of the Statia Marine Park habitats sampled and were concentrated in the shallow wave-exposed eastern parts of the island (7.7 m average depths). The densest coral “scapes” and seagrass beds of St. Eustatius were concentrated at depths of about 24 m and only amounted to 4 and 5 percent resp. of the island shelf habitats studied. Whereas coral areas were essentially limited to the southern and south-western island shelf areas, seagrass beds were confined to the northern island shelf area. Including patch reef habitats, total hard coral-scape habitat for the St. Eustatius Marine Park amounted to about 19% of the area surveyed and about 475 ha of habitat. Sargassum reef habitat typically occurred at the seaward edge of communities dominated by hard coral growth.
Sponges are major epibionts of mangrove roots in the Caribbean. Mangrove sponge communities in the Caribbean mainly consist of species that are typical to this habitat and community compositions often differ from those found on coral reefs nearby. Heterogeneity in species distributions between locations and within locations between roots is often reported. This study quantifies the diversity and abundance of mangrove associated sponges in the inner bays of Curaçao and Aruba and correlates variability of regional sponge diversity with environmental variables measured along the surveyed sites. Tannin concentrations vary between mangrove roots, and were correlated to sponge cover as a possible cause for habitat heterogeneity on a smaller scale. A total of 22 species was observed. Heterogeneity in species richness and abundance was apparent, and several sponge species were restricted in their depth of occurrence. Statistical data reduction suggests that sponge diversity may be partly explained by the distance towards adjacent reefs and to the degree of eutrophication, in which the latter is comprised of rate of planktonic respiration, total carbon and turbidity. Tannin concentrations did not determine within locality species heterogeneity as a priori postulated, but were positively related to sponge cover for reasons not yet elucidated.