Brazilian coral reefs form structures significantly different from the well-known reef models, as follows: (i) they have a growth form of mushroomshaped coral pinnacles called "chapeirões", (ii) they are built by a low diversity coral fauna rich in endemic species, most of them relic forms dating back to the Tertiary, and (iii) the nearshore bank reefs are surrounded by siliciclastic sediments. The reefs are distributed in the following four major sectors along the Brazilian coast: the northern, the northeastern and the eastern regions, and the oceanic islands, but certain isolated coral species can be found in warmer waters in embayments of the southern region. There are different types of bank reefs, fringing reefs, isolated "chapeirões" and an atoll present along the Brazilian coast. Corals, milleporids and coralline algae build the rigid frame of the reefs. The areas in which the major coral reefs occur correspond to regions in which nearby urban centers are experiencing accelerated growth, and tourism development is rapidly increasing. The major human effects on the reef ecosystem are mostly associated with the increased sedimentation due to the removal of the Atlantic rainforest and the discharge of industrial and urban effluents. The effects of the warming of oceanic waters that had previously affected several reef areas with high intensity coral bleaching had not shown, by the time of the 2010 event, any episodes of mass coral mortality on Brazilian reefs. AbstrActDescriptors: Coral reefs, Global changes, Coral bleaching, Endemic fauna.Os recifes de coral do Brasil formam estruturas significativamente diferentes dos modelos conhecidos: (i) possuem uma forma de crescimento de pináculos coralíneos em forma de cogumelo, chamados "chapeirões", (ii) são construídos por uma fauna coralínea com baixa diversidade e rica em espécies endêmicas, sendo grande parte destas formas relíquias do período Terciário e (iii) os recifes costeiros estão num ambiente dominado por sedimentos siliciclásticos. Os recifes estão distribuídos em quatro áreas ao longo da costa brasileira: regiões norte, nordeste, leste, e nas ilhas oceânicas, mas espécies isoladas de coral podem ser encontradas em águas mais quentes nas enseadas da região sul. Diferentes tipos de banco recifais, recifes em franja, "chapeirões" isolados e um atol estão presentes ao longo da costa brasileira. Corais, milleporídeos e algas coralinas incrustantes constroem a estrutura rígida dos recifes. As áreas em que ocorrem os maiores recifes de coral correspondem às regiões nas proximidades de centros urbanos que estão experimentando crescimento acelerado e rápido desenvolvimento do turismo. Os principais efeitos antropogênicos sobre o ecossistema recifal estão associados, essencialmente ao aumento da sedimentação devido à remoção da mata atlântica e as descargas de efluentes industriais e urbanos. Os efeitos do aquecimento das águas oceânicas que vem afetando várias áreas de recifes, com alta intensidade de branqueamento de coral, não causaram mortalidade em massa ...

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Experiments were performed on the Great Barrier Reef, at Orpheus lsland (18" 40'S, 145" 30' E) and Lizard Island (14" 41' S, 145" 28' E), Australia, to examine allelopathic effects of soft corals on the larval recruitment of scleractinian corals. Ceramic tiles were used as settlement plates and arranged around the soft corals Sinularia flexibilis (Quoy & Gaimard) and Sarcophyton glaucurn (Quoy & Gaimard), serving as treatments. One control consisted of stacks of settlement plates uninfluenced by any organism, while a second control had settlement stacks surrounding a scleractinian coral to control for depletion of larvae via feeding. Coral spat recruitment was approximately 7 times higher at Lizard Island (7032) than at Orpheus lsland (1038). The pattern of coral recruitment and relative abundances of coral recruits around the controls and soft corals, however, was similar at the 2 sites. The average density of coral spat was always significantly less around the soft corals than the controls, indicating that soft corals at each experimental site inhibited scleractinian coral recruitment. Coral recruitment levels were very similar for the 2 control treatments. Coral spat were asymmetrically distributed around the soft corals, and the distribution varied significantly with respect to the distance from the soft coral and the direction of the prevailing current at both Orpheus and Lizard Island. There was a significant negative correlation between coral spat density and current direction under both soft coral treatments and at both sites. No such response was observed in the controls. In a second experiment, scleractinian coral spat were exposed to settlement plates impregnated with the extract of S. flexibilis and control plates. Settlement only occurred on the untreated controls.

Colonies of the soft coralSinularia flexibilis (Quoy & Gaimard) (Coelenterata, Octocorallia) were collected at Lizard Island (14°40'S and 145°28'E) Research Station. Extraction of the corals and quantitative chemical analysis for the three major diterpene components, flexibilide, dihydroflexibilide, and sinulariolide, afforded average ratios of 4∶3∶1 respectively. Colonies, sized on the basis of the sterile stalk circumference, were analyzed for possible correlations between size and chemical composition. The major metabolite, flexibilide, was inversely correlated with colony size, while sinulariolide concentration showed a direct correlation. The concentration of dihydroflexibilide was independent of colony size. Samples were further analyzed with respect to site of collection. Colonies were collected at three distinct reefal sites. One was characterized by large monospecific stands ofParites cylindrica, a second was a sandy bottom site with a mixed community of soft corals and occasional scleractinians, while the third site was a very diverse reef community with many species of scleractinian corals.Sinularia flexibilis was well represented at each site, and the concentration of flexibilide and sinulariolide varied significantly among sites. The concentration of flexibilide was significantly higher at the third, highly competitive site, while the concentration of sinulariolide was highest at thePorites-dominated site. Dihydroflexibilide levels were independent of site. It seems likely that concentrations of flexibilide, a highly cytotoxic molecule involved in interference competition, and sinulariolide, a known algicide probably responsible for colony maintenance, may be influenced by their environments.