Abstract:The 1983-1984 mass mortality event of Diadema antillarum affected more than 93% of the total Caribbean population. Although there are no records about the status of Diadema populations before and after die-off on Cuban reefs, anecdotal information suggests that populations were struck. We analyzed spatial variation in the abundance and size structure of D. antillarum in 22 reefs sites in Jardines de la Reina, from June 2004 to September 2005. Counts of Diadema were performed in five 30x2m transects at each sampling site and sampling time, and test diameters were measured in September 2005 at the same fore reefs. Abundances were higher at reef crests (mean densities 0.08-2.18 ind./m 2 ), while reef slope populations reached a maximum site level of 0.13 ind./m 2 at only one site and showed values up to three orders of magnitude lower than those from reef crests. Highest abundance occurred at the west margin of major channels between keys where larval recruitment seems to be favored by local oceanographic features and facilitated by the abundance of Echinometra lucunter. The size frequency distribution of D. antillarum indicates that recruitment began to be noticeable three years before September 2005, suggesting these populations were depleted in the past and they are recovering now. Rev. Biol. Trop. 58 (2): 663-676. Epub 2010 June 02.

The 1983-1984 mass mortality of Diadema antillarum produced severe damages on Caribbean reefs contributing to substantial changes in community structure that still persist. Despite the importance of Diadema grazing in structuring coral reefs, available information on current abundances and algal-urchin interactions in Cuba is scarce. We analyzed spatial variations in Diadema abundance and its influence on algal community structure in 22 reef sites in Jardines de la Reina, in June/2004 and April/2005. Urchins were counted in five 30x2m transects per site, and algal coverage was estimated in randomly located 0.25m side quadrats (15 per site). Abundances of Diadema were higher at reef crests (0.013-1.553 ind/m 2 ), while reef slope populations showed values up to three orders of magnitude lower and were overgrown by macroalgae (up to 87%, local values). Algal community structure at reef slopes were dominated by macroalgae, especially Dictyota, Lobophora and Halimeda while the most abundant macroalgae at reef crests were Halimeda and Amphiroa. Urchin densities were negatively and positively correlated with mean coverage of macroalgae and crustose coralline algae, respectively, when analyzing data pooled across all sites, but not with data from separate habitats (specially reef crest), suggesting, along with historical fish biomass, that shallow reef community structure is being shaped by the synergistic action of other factors (e.g. fish grazing) rather than the influence of Diadema alone. However, we observed clear signs of Diadema grazing at reef crests and decreased macroalgal cover according to 2001 data, what suggest that grazing intensity at this habitat increased at the same time that Diadema recruitment began to be noticeable. Furthermore, the excessive abundance of macroalgae at reef slopes and the scarcity of crustose coralline algae seems to be due by the almost complete absence of D. antillarum at mid depth reefs, where local densities of this urchin were predominantly low. Rev.

En los años 2001 y 2005, se estudió la composición de las comunidades de octocorales y corales pétreos en el archipiélago de los Jardines de la Reina. Se analizó, en la comunidad de corales pétreos, la incidencia del blanqueamiento ocurrido en el 2005 en el Caribe. Para ello se establecieron doce estaciones de muestreo (siete en el arrecife frontal somero y cinco en el arrecife de cresta), en cada una de estas se estimó la densidad mediante el marco cuadrado de 1 m de lado. En el arrecife frontal somero se identificaron un total de 62 especies (26 de octocorales y 36 de corales), siendo las más abundantes: Pseudopterogorgia americana (2.4 colonias/m2), Eunicea flexuosa (1.1 colonias/m2), Siderastrea siderea (5.0 colonias/m2) y Agaricia agaricites (4.0 colonias/m2). En el arrecife de cresta se identificaron un total de 31 especies (13 de octocorales y 18 de corales), predominando: Briareum asbestinum (1.3 colonias/m2), Porites astreoides (2.5 colonias/m2) y Millepora complanata (1.0 colonias/m2). Las especies más sensibles al blanqueamiento fueron: A. agaricites , Millepora spp. y Montastraea annularis. En sentido general, dicho suceso tuvo una incidencia pobre sobre los corales pétreos. Es menester la ejecución de monitoreos al permitir ajustar los planes de manejo en función de los cambios que puedan ocurrir en la estructura de las comunidades bentónicas.ABSTRACT Octocoral and stony coral communities in the Jardines de la Reina archipelago (Cuba) were studied in 2001 and again in 2005. The incidence of the 2005 bleaching event in the Caribbean was analyzed in the stony coral community. Twelve sampling stations were established: seven in the shallow forereef and five in reef crests, with one square meter quadrants to estimate density. A total of 62 species (26 octocorals and 36 stony corals) were identified in the shallow forereef, including Pseudopterogorgia americana (2.4 colonies/m2), Eunicea flexuosa (1.1 colonies/m2), Siderastrea siderea (5.0 colonies/m2) and Agaricia agaricites (4.0 colonies/m2). In the reef crest, 31 species were identified (13 octocorals and 18 stony corals), with Briareum asbestinum (1.3 colonies/m2), Porites astreoides (2.5 colonies/m2) and Millepora complanata (1.0 colonies/m2) being the most abundant. The most sensitive species to bleaching were: A. agaricites, Millepora spp. and Montastraea annulariS. In general, this event showed a poor incidence with stony corals. Constant monitoring is necessary to adjust the management plan to the changes that may occur in the structure of the benthic communities.