Effects of variation in eutrophication and in Diadema antillarum densities (grazing pressure) on the abundance and life history characteristics of Favia fragum on seven reefs along the west coast of Barbados were investigated. Densities of D. antillarum were negatively correlated with eutrophication levels, and interpretations of their effects have been made simultaneously. Abundance of F. fragum was lower on more eutrophic reefs with lower D. antillarum densities. This may result from effects of eutrophication and of D. antillarum on algal cover on reefs. Macrophytic algae were more abundant, and crustose coralline algae less abundant, on eutrophic reefs with lower D. antillarum densities; and macrophytic algal cover was negatively correlated with crustose coralline algal cover across reefs. F. fragum abundance was positively correlated with crustose coralline algal cover, and F. fragum occurred less frequently on reef areas where macrophytic algae were abundant. High eutrophication and low D. antillarum density (grazing pressure) may therefore reduce F. fragum abundance by increasing the cover of macrophytic algae relative to crustose coralline algae on reefs. Neither planulation periodicity, colony fecundity, nor polyp fecundity in F. fragum differed at different eutrophication levels and D. antillarum densities. Moreover, adult growth and adult mortality did not differ with eutrophication levels and D. antillarum densities on reefs. However, growth of juveniles appeared slower and mortality higher on eutrophic reefs with low D. antillarum densities. Moreover, larvae of F. fragum preferred to settle on crustose coralline algae than on turf algae (macrophytic algae), and the former are comparatively scarce on eutrophic reefs with low D. antillarum densities. The results suggest that the negative correlation between adult abundance of F. fragum and eutrophication levels/grazing pressure (D. antillarum densities) on Barbados reefs are caused primarily by effects

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This study investigates effects of eutrophication on settlement, abundance, mortality and community structure of soleractinian corals on fringing reefs on the west coast of Barbados, W.I. Juvenile abundance was lower, but juvenile size larger, on eutrophic than less eutrophic reefs. The lower abundance results at least in part from a higher juvenile mortality on eutrophic reefs. Algae were more abundant and grazers (Diadema antillarum and herbivorous fish) less abundant on eutrophic reefs. Juvenile community structure on all reefs, and adult community structure on eutrophic reefs, was dominated by type 1 corals (high recruitment, high natural mortality). Type 2 corals (low recruitment, low natural mortality) were common in adult communities on less eutrophic reefs. Settlement of coral recruits on artificial substrates was lower on more eutrophic reefs.

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No description available.

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.)

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.

No description available.

No description available.

No description available.