El blanqueamiento coralino es asociado frecuentemente con temperaturas inusualmente cálidas, pero también puede ocurrir durante episodios de enfriamiento del agua. En esta nota registramos un evento de blanqueamiento coralino, especialmente en Porites lobata, después de las temperaturas del mar más bajas registradas para Malpelo en 21 años. En abril de 2009 observamos blanqueamiento en cuatro de las diez especies coralinas registradas en la isla Malpelo. Este evento fue más frecuente (hasta el 72 % de las colonias) y extenso (hasta el 87 % del área de la colonia) en P. lobata. La temperatura superfiial del mar obtenida por satélites alcanzó valores tan inusualmente bajos como 23.1 °C en marzo de 2009 con anomalías térmicas hasta de -4.4 °C. Un sensor de temperatura instalado a 20 m de profundidad indicó que la temperatura fue altamente variable durante el episodio frío disminuyendo hasta 15.8 °C en febrero de 2009. Una conjunción de la temporada de bajas temperaturas, condiciones similares a las de La Niña y otros factores no identifiados parecen haber causado un episodio de descenso extremo de la temperatura que provocó una respuesta de blanqueamiento en P. lobata, un coral sensible al enfriamiento del agua.
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.
We present evidence of coral sexual recruitment, which has typically been low in the Eastern Tropical Pacific, on coral reefs and rocky sites of Gorgona Island, Colombia, and for the first time in the Colombian Pacific. With data obtained by thoroughly examining natural substrates, coral juveniles of at least ten species were found at ten out of 19 sites surveyed during scuba diving explorations performed around the island between 2010-2017; however, no corals were found on settlement plates of five different materials. The two most abundant coral species found as juveniles were Porites panamensis and Pocillopora sp., occurring at mean densities of 5.7 ± 4.7 and 0.07 ± 0.11 colonies m-2 (± SD), respectively, and with mean colony-sizes of 2.3 ± 0.9 cm and 3.5 ± 1.0 cm (± SD), respectively. These results indicate that, even though settlement plates do not seem to be as useful to study coral recruitment in the region as they are elsewhere, coral recruitment derived from the sexual reproduction of a diverse set of species is an active process at Gorgona Island.
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