Soil erosion is a long standing problem in the Scotland District of Barbados. Many workers, including pedologists, geologists, hydrologists and soil conservationists have recently undertaken investigation into the causes of soil erosion and the possible means of its control. These studies have focussed on a problem in a restricted field. As accelerated soil erosion is an important ecological process, it was felt that an investigation into the problems of erosion from an ecological viewpoint was necessary. [...]

This study investigates the characteristics and use of spawning sites by the bluehead wrasse Thalassoma bifasciatum in Barbados, and movements of wrasses from source reefs to proximate and isolate recipient reefs. Pair spawning rate increased with increasing projection height; group spawning rate increased with increasing proximity to the downcurrent reef edge. Daily group spawning rates, but not pair-spawning rates, were higher when daily current speeds were lower, suggesting that fertilisation rates in group spawns may be more sensitive to current speed than fertilisation rates in pair spawns. Migration rate to isolated reefs was 16% that to proximate reefs. Immigration rate to recipient reefs decreased with increasing distance from the source reef and increased with increasing population density on the source reef. Immigration rates to proximate reefs were phase, sex, and size-specific, and were strongly influenced by phase, sex, and size-specific differences in home range size of wrasses. Immigration to isolated reefs was also phase and sex-specific. (Abstract shortened by UMI.)

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Samples of Porites porites rubble were collected from across three fringing reefs which lie along a eutrophication gradient in Barbados, West Indies. The coral skeleton fragments were examined for clionid sponges. Data collected from the reef crest and fore reef zones and from across the range of distances and depths were pooled for each reef to compare indices of sponge abundance along the eutrophication gradient. Significant differences between the reefs were found for the proportion of rubble invaded (ANCOVA, p = 0.004), number of invasions per sample (ANCOVA, p = 0.002), and number of species per sample (ANCOVA, p = 0.018) but not for total surface area of sponge invasions per sample (ANCOVA, p = 0.064). All the indices demonstrated an increase with increasing eutrophication level. Clionids were found in nearly twice as many of the pieces collected from the most eutrophic site (41%) as from the least eutrophic (24%). Since clionids may be the principal bioeroders of coral reefs, an increase in their abundance due to excessive pollution likely results in greater bioerosion of affected reefs. The mean abundance of Type 3 corals was found to be positively related to the frequency of boring sponge invasion, suggesting that increased bioeroision may be partly responsible for community shifts toward Type 3 corals in polluted waters. One new variety and three new species of boring sponges of the genus Cliona were found. A new variety of C. amplicavata Rutzler is described, Cliona species 2 of MacGeachy is redescribed and Cliona species 4 and Cliona species 5 are described for the first time. Cliona species 5 may become an important bioeroder in Barbados and other Caribbean islands since it flourishes under high eutrophic conditions which are beginning to plague West Indian reefs. (Abstract shortened by UMI.)

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Multivariate ordination techniques were used to characterize the direction and magnitude of coral community changes on west coast reefs in Barbados between 1982 and 1992, and to relate these changes to coastal eutrophication and variation in Diadema antillarum densities (grazing pressure). D. antillarum densities were substantially lower in 1992 than in 1982, reflecting the 1983 mass mortality event. Reductions in urchin density were greater on less eutrophic reefs than eutrophic reefs. Cover by macrophytic algae increased, cover by crustose coralline algae decreased, and the number of coral species decreased between 1982 and 1992. With the notable exception of the most eutrophic reef, coral cover decreased over the 10 year period. Changes in algal cover across reefs between 1982 and 1992 were strongly correlated with decreases in D. antillarum densities, and were therefore typically greater on less eutrophic reefs, indicating that reduced grazing pressure has more strongly influenced algal cover changes than prevailing eutrophication levels. Coral species composition changed at all sites between 1982 and 1992, and except at the most eutrophic site, the direction of change was directly related to reduced D. antillarum densities and associated algal cover changes. Temporal change at the most eutrophic site was best explained by the prevailing high level of eutrophication, and resulted primarily from a substantial increase in the cover of one species, Porites porites. The decrease in coral cover that occurred on most of the study reefs in the face of the increasing cover by macrophytic algae was typically accompanied by an increase in the relative abundance of Type 1 (high recruitment, high natural juvenile mortality) to Type 2 (low recruitment, low natural juvenile mortality) corals.