NOTES ON THE DISTRIBUTION, HABITAT AND MORPHOLOGY OF STYLASTERROSEUS (PALLAS 1766) (HYDROZOA: STYLASTERINA) IN THE COLOMBIAN CARIBBEAN.

Stylaster roseus en el Caribe colombiano es un común habitante de sus arrecifes coralinos, exceptuando la región de Santa Marta y la Guajira. S. roseus es una especie críptica que tiende a ubicarse en sitios sombreados, generalmente bajo o entre ramas de coral muerto o vivo. Se le observó entre esqueletos de Acropora palmata (2-6 m), sobre las partes laterales e internas de pináculos de Millepora (0.5-3 m), bajo tejados de Montastraea annularis y Agaricia spp. (15-30 m), y sobre embarcaciones hundidas (5-20 m). Adicionalmente se encontró creciendo sobre tejido vivo de Millepora, No se encontraron diferencias en las medidas promedio de colonias de hábitats similares. La coloración más común fue tronco blanco y ramas púrpura, seguida por la púrpura uniforme. Las formas dominantes en su orden fueron: las flabeladas o uniplanares, las ramificadas en dos planos y las arborescentes.

BENTHIC COMMUNITIES AND GEOMORPHOLOGY OF THE TESORO ISLAND CORAL REEF, COLOMBIAN CARIBBEAN

The benthic communities distribution in Tesoro Island (Colombian Caribbean) coral reef was determined by cartography of reef morphology and functional groups from aerial photographstheodolite triangularon, and bottom transects over depths ranging from Oto 30 m. Tesoro Island is a sand cay reef developed over an emerged reef platform whose basal cone possibly originated by mud diapirism on the continental shelf. The benthic communities are distributed as subzones of the geomorphologic units. The reef crest lies along the breaker zone, formed by Millepora spp. buttresses covered on their tops by Palythoa spp. and seawardly by a turf of Dictyota spp. The rear reef (varying from 0.5-1.5 m in depth) is composed of pavement and grooves with live Pontes pontes and P. astreoides. The foré-reef terrace (2 to 9 m in depth) shows a low relief spur and grooves, composed of Acropora pa/mata skeletons on the windward side and A. cervicornis on the leeward side; sandy accumulations with dense and tall colonies of the gorgonaceans Pseudopterogorgia spp. are also appreciated. In the sandy reef platform there are monospecific patches of Montastraea annularis, P. pontes, M. faveolata, dead Acropora cervicornis and wide sandy zoneswhere patches of Halimedamonile are found. The slope edge, (depths ranging between 7 to >30m) shows mixed corals and gorgonaceans, at the drop-off, laminar corals, especially Montastraea franksiand Agaricia spp., jointly with other deep water organisms such as ellisellid gorgonaceans and antipatharians are found. The benthic communities distribution is influenced by reef geomorphology, wave energy diffraction and the past mass mortality of Acropora.

ANNUAL SKELETAL EXTENSION OF TWO REEF-BUILDING CORALS FROM THE COLOMBIAN CARIBBEAN SEA

The skeletal growth of the scleractinian corals Diploria labyrinthiformis (Linnaeus 1758) and Montastraea annularis (Ellis and Solander 1786) from Isla Grande (north of Rosario islands), Colombian Caribbean, was determined from annual extension increments revealed by X-radiography of 4-6 mm thick slabs obtained along the axis of maximum growth. The skeletal extension average rate for the last 22 years for D. labyrinthiformis was 3.8 mm year-1 (SE 0.10; N = 87). The correlation between growth of D. labyrinthiformi s and hours of sunlight was significantly negative. The annual variances of sunlight enhanced annual statistically significant differences of growth in this species. M. annularis showed an average extension growth of 10.6 mm year-1 (SE 0.32; N = 55) during the last 14 years. The increase of M. annularis growth was coincident with the end of nearby dredging activities as well as the decrease of nutrient levels. Nevertheless, the growth rate of this species showed no statistically significant differences through the years and no correlation with variation in sunlight. Alow density annual band, wider than high density band in D. labyrinthiformis and narrower in M. annularis, seems to form approximately during April and May in both species, which is coincident with the end of dry season (increase of sea surface temperature, decrease of hours of sunlight and high influence of Dique Channel waters over Rosario islands). The annual bands forming on both species at the study site might be highly related with time of reproduction of each species. Further investigation will permit a better understanding of how some local conditions or coral physiology are related with coral growth at Rosario islands.

FERTILIDAD Y FECUNDIDAD DE MONTASTRAEA ANNULARIS EN UN ARRECIFE DEGRADADO

This study determined the gametogenic cycle, fecundity and fertility of Montastraea annularis, in the Isla Grande coral reef, Archipelago of Nuestra Señora del Rosario, one of the most degraded reefs in the Colombian Caribbean. The surveyed population is currently characterized by medium size colonies (ca. 3379 cm2), with 27 % of the ramets showing partial mortality and 10 % with total mortality. Colonies present high number of small sized ramets formed by !ssion (76 %, smaller than 50 cm2). Based on the above mentioned population structure characteristics, the aim of this research was to explain the low recruitment rate reported for this reef through the reproductive response of a population dominated by small ramets. Between September 2003-2004, tissue fragments were collected and histological slides were made to detail the development of oocytes and spermaries and to estimate fecundity. Additionally during September of 2003 and 2004, in situ spawned eggs were collected to quantify fecundity. Results showed that oogenesis occurred between May and September and the spermatogenesis between July and September. Fertility was low (35 % and 40 %, in situ and histology, respectively) as well as fecundity (20 and 11 eggs/cm2/year-1, in situ and histology, respectively). Of the 33 % of ramets that showed spermaries, only 3 % of the mesenteries presented male gametes and in these, the presence of sperm cysts was also scarce (4 espermaries/gonad). Although the size of the ramets did not show a statistical relationship with fertility or fecundity, ramets between 50 and 100 cm2 were found more fecund than smaller (<50 cm2) or larger ramets (>200 cm2). The poor reproductive effort found can, in part, explain the low number of small colonies in the studied population, which in turn is expected in degraded sites and in populations with high !ssion rates. The results suggest that the viability of the population of M. annularis at Isla Grande is de!ned by the low number of fertile ramets and the low fecundity, but especially by low production of male gametes.

COMPARACIÓN TEMPORAL EN LA ESTRUCTURA DE UNA COMUNIDAD CORALINA EN PRIMEROS ESTADOS DE SUCESIÓN, ISLA DE SAN ANDRÉS, COLOMBIA

The coral reefs worldwide have suffered a decline during the past three decades. These changes have been evaluated in fringing reefs; nevertheless, it is not known if the factors causing those changes affect the coral community dynamics during the !rst states of the succession, before the development of a reef. To resolve this question, during 2004, 2005, and 2006 we monitored an isolated coral community in San Andres. We compared trough time the abundance, coverage and partial mortality suffered by the coral community and its dominant coral populations. The coral community did not present statistical variation in richness, abundance, coverage, neither in the area of partial mortality. However, this community did change in composition with the entry of two coral species (Acropora cervicornis and Scolymia cubensis) and the exit of other two coral species (Diploria clivosa and Siderastrea siderea) suggesting local processes of extinction (caused possibly by sedimentation and resuspension) and colonization (dispersion). Although the coral community as a whole showed stability, the partial mortality of three of its dominant species (Montastraea annularis, Porites astreoides and Colpophyllia natans) increased and the coverage of Agaricia agaricites diminished over time (been the population more sensitive in this system). These results suggest similar but faster dynamic when compared to the theory reported to advanced stages of reef development (fringing reefs), where the more sensitive variables appeared at population rather than community level, partial mortality being the most important factor explaining the rate of replacement of species (composition), the annual lost of coral coverage, and changes in colonial size distribution of the dominant populations.

COBERTURA DE LOS FONDOS Y PAISAJES BENTÓNICOS ASOCIADOS A FORMACIONES DIAPÍRICAS EN LOS BANCOS DE SALMEDINA, PLATAFORMA CONTINENTAL DEL CARIBE COLOMBIANO

The submarine ecological units around an active mud volcano in the offshore banks of Salmedina, Colombian Caribbean, were determined and mapped employing geo-referenced submarine video-transects, bathymetry analysis, and interpretation of satellite imagery. Distribution, relative cover, and the most representative benthic, sessile organisms of the different ecological units are described. In the shallow zone of the banks, 60 % of the substrate was covered by algae and only 10 % by living corals. The relative cover of living corals in deeper zones increased to 33 % in semi vertical slopes and up to 55 % on the upper flats of deeper located banks. The dominant coral species overall were Siderastrea siderea and Montastraea annularis. A determining natural factor in the reef structure in the zone seems to be recent diapiric activity, with a constant mud emanation in the western sector. The Banks of Salmedina are under the influence of turbid plumes that seemingly increase sedimentation and are impacted by blast fishing as well. Although the shallowest zone of the bank shows the highest affectation, the coral community in the deeper zones still exhibit a noticeable cover of living coral, even higher than in other areas in the region with similar features. The recent diapiric activity of constant mud ejection determines the coral community structure in the western sector.

Static measurements of the resilience of Caribbean coral populations

<span>En la actualidad se está viendo en el Caribe un cambio en la composición de los corales constructores de arrecifes, aumento en la cobertura de macroalgas y otras especies, un aumento en áreas cubiertas por escombros de corales, y una pérdida de relieve. La incorporación de principios de resiliencia en el manejo es una estrategia propuesta para revertir esta tendencia y asegurar la sobrevivencia y el adecuado funcionamiento de los arrecifes de coral bajo escenarios previstos de cambio climático. Sin embargo, todavía quedan grandes vacíos en la comprensión de los factores que promueven la resiliencia. Evaluaciones rápidas realizadas con la metodología AGRRA (Atlantic and Gulf Rapid Reef Assessment) y con el protocolo de Evaluación de Resiliencia para arrecifes coralinos de la IUCN brindan información de línea base sobre la resiliencia de los arrecifes del Caribe. Un aspecto clave de estos estudios se centra en la dinámica de las poblaciones de los corales, incluyendo medidas de cobertura de coral, estructura de tallas, la extensión de la mortalidad parcial y total de toda la comunidad, condición de los corales y reclutamiento. Un reto es que esto representa una medida estática que involucra una única evaluación. Sin seguir las colonias individuales y el reclutamiento en el tiempo, es difícil determinar las tasas de sobrevivencia y crecimiento de los reclutas, y podría no ser posible la diferenciación de los juveniles de los restos pequeños de colonias más viejas, especialmente cuando la cobertura algal es alta. Para abordar esta limitación, los corales monitoreados en Bonaire en julio del 2010 fueron subdivididos en dos categorías: 1) colonias sobre la estructura arrecifal; y 2) colonias creciendo sobre coral muerto o sobre las superficies expuestas del esqueleto de los corales vivos. Los arrecifes en Bonaire exhiben muchas características indicativas de alta resiliencia, incluyendo una alta cobertura de coral (frecuentemente 30-50%), altos niveles de reclutamiento, y un gran número de corales que se asentaron sobre los corales muertos y crecieron. En general, las superficies del esqueleto de 12 especies de corales fueron colonizadas por 16 especies de corales, con un máximo de 12 colonizadores en cada colonia, la mayoría (67%) sobre esqueletos de <em>Montastraea annularis</em> (complejo). Colonias completamente muertas de M. annularis fueron comunes y los sobrevivientes con frecuencia son más pequeños o subdivididos en pequeños restos de tejido. Montastraea annularis es la especie que exhibe una mayor mortalidad parcial en relación con los demás corales. Una notable ausencia de reclutamiento sexual y juveniles de <em>M. annularis</em> ilustra el cambio progresivo de cambio de un sistema dominado por Montastraea. Este cambio, que se está produciendo en todo el Caribe, se caracteriza por un dominio cada vez mayor de especies más pequeñas y de vida corta como Agaricia y Porites, y una reducción en el tamaño de los corales masivos longevos. El seguimiento de la sobrevivencia de los reclutas es necesario para determinar si los arrecifes del Caribe mantendrán la misma función, estructura, identidad y retroalimentación (signos clave de la resiliencia), y si las pérdidas de M. annularis (complejo) continuarán a los niveles actuales. La evaluación rápida presentada aquí posibilita caracterizar la estructura de tamaño de las colonias, los niveles de reclutamiento y determinar si los corales pequeños representan sobrevivientes de colonias que incrementan su tamaño o colonias grandes (más viejas) que siguen disminuyendo de tamaño. Este enfoque puede ayudar a determinar la historia de un sitio y su capacidad de recuperación.</span>

Insights into Migration and Development of Coral Black Band Disease Based on Fine Structure Analysis

<span>En muchos ecosistemas diversos, que van desde ecosistemas acuáticos hasta los intestinos de mamíferos e implantes médicos, las poblaciones y comunidades de bacterias existen como biopelículas (biofilms). El proceso de desarrollo de las biopelículas ha sido bien estudiado para aquellos producidos por bacterias unicelulares como<em> Pseudomonas aeruginosa</em>, pero se conoce muy poco acerca del desarrollo de biopelículas asociadas con microorganismos filamentosos. La Enfermedad de Banda Negra (EBN) de coral es caracterizada como una comunidad polimicrobiana que forma una biopelícula (lecho), visualmente-dominada por una cianobacteria filamentosa. El lecho migra a través de un huésped de coral vivo, rompiendo completamente el tejido del coral y dejando atrás el esqueleto de coral expuesto. Es la única biopelícula cianobacteriana que migra a través de un sustrato, por lo tanto esto genera preguntas acerca de los mecanismos y las características únicas de este sistema. Fragmentos del coral <em>Montastraea annularis</em>, cinco artificialmente infectados con EBN y dos colectados de una colonia EBN-infectada, fueron usados para abordar estas preguntas mediante exámenes detallados con microscopía electrónica de barrido y de transmisión (MEB y MET). En zonas cercanas a la interfaz de tejido del coral y la banda de la enfermedad madura, se han observado dos tipos de grupos de cianobacterias, uno con orientación aleatoria y otro con una orientación paralela de los filamentos. Este último exhibe la secreción activa de polisacáridos extra-celulares (PEC), mientras que los grupos orientados al azar no lo hicieron. Dentro de la banda de filamentos cianobacterianas bien desarrollados se observó que estaban integradas en PEC y que se presentaban como capas de cianobacteria con orientación paralela. Estas observaciones sugieren que la cianobacteria de EBN se orienta a sí misma y produce PEC en un proceso secuencial durante la migración para formar la matriz complejo de EBN.</span>

Sipunculans associated with dead coral skeletons in the Santa Marta region of Colombia, south-western Caribbean

Sipunculans represent a discrete component of the coral reef ecosystem, since they live inside the calcareous structure. They are an important component in terms of biomass and number of organisms. The present study describes the diversity of sipunculans living inside massive coral skeletons. A total of 43 blocks of dead coral skeletons from Montastraea cavernosa, Montastraea annularis and Diploria strigosa were collected from nearby coral reef areas off Santa Marta, on the Colombian Caribbean coast. Using hammer and chisel, blocks of approximately 1 dm3 were broken into small pieces, from which the sipunculans were extracted. A total of 381 organisms were obtained from the coral blocks comprising four families and 10 species. All the species found have been widely reported in different studies from the Caribbean region. Aspidosiphon fischeri and Phascolosoma perlucens were the two most abundant species comprising more than 60% of the total organisms with a mean density of 18.52 ± 4.64 organisms dm−3. Dead coral substrate from M. cavernosa had the greatest abundance (N = 148), followed by D. strigosa (N = 121) and M. annularis (N = 112). There were no significant differences in the abundance, richness, and diversity of sipunculans between coral skeletons; and within samples there was high variability suggesting that the skeletal substrates analysed came from coral skeletons of different unknown ages of succession. These results describe the sipunculan community structure that live inside three important massive coral skeletons, and contributes to the knowledge of the cryptobiota diversity of the Santa Marta area of Colombia.