Coral recruitment to two vessel grounding sites off southeast Florida, USA / Reclutamiento de coral en dos sitios de encallamiento de embarcaciones frente al sureste de Florida, EE. UU

Over the last two decades, more than 10 major vessel groundings have occurred on coral reefs offshore southeast Florida. Lack of any published information on coral settlement, post-settlement survival, and juvenile coral growth in the southeast Florida region inhibits efforts to determine if coral populations will be able to effectively re-establish themselves. The goal of this study was to examine these processes to obtain background data needed to determine the potential for natural recovery. Over a three year period annual coral recruitment, juvenile growth, and mortality rates were measured in 20 permanent quadrats at each of two ship grounding and two control sites. The density of new recruits was generally low, ranging from 0.2±0.1 (SE) to 7.1±1.0 recruits m-2. Although the density of coral recruits was generally higher at the grounding sites, mortality rates were high at all sites during the study period. Growth rates of individual colonies were highly variable, and many of the colonies shrank in size due to partial mortality. Results indicate that corals are able to recruit to the damaged reefs but that slow growth rates and high mortality rates may keep these areas in a perpetual cycle of settlement and mortality with little or extremely slow growth to larger size classes, thus inhibiting recovery.

En las dos últimas décadas, más de10 grandes encallamientos de embarcaciones se han producido en los arrecifes de coral mar afuera en el sureste de Florida. La falta de información publicada sobre el asentamiento de corales y sobrevivencia post-asentamiento y de los corales juveniles que crecen en la región, limita los esfuerzos para determinar si las poblaciones de coral serán capaces de restablecerse por ellas mismas. El objetivo de este estudio fue examinar estos procesos para obtener la información necesaria para determinar el potencial de recuperación natural. Se midió el reclutamiento anual de coral joven, el crecimiento y las tasas de mortalidad por un período de tres años, mediante 20 cuadrantes permanentes en cada uno de los dos encallamientos de barcos y dos sitios de control. La densidad de nuevos reclutamientos fue generalmente baja, de 0.2±0.1 a 7.1±1.0 reclutamientos m-2. Aunque la densidad del reclutamiento fue generalmente más alta en los sitios de encallamiento también hubo mayor mortalidad de corales juveniles en esos sitios durante el período de estudio. Las tasas de crecimiento de las colonias individuales fueron altamente variables, y muchas de las colonias se redujeron en tallas debido a mortalidad parcial. Los resultados indican que los corales presentan una disposición a reclutarse en arrecifes dañados, pero las lentas tasas de crecimiento y la alta mortalidad pueden mantener esas áreas en un perpetuo ciclo de asentamiento y mortalidad con poco o extremadamente lento crecimiento hacia las clases de tallas largas, por lo tanto inhibiendo la recuperación.

Coral recruitment patterns in the Florida Keys

This study examines scleractinian zooxanthellate coral recruitment patterns in the Florida Keys to determine if differences in density or community composition exist between regions. From July to September 2002, nine patch reefs, three in each of the upper, middle and lower Keys, were surveyed for coral recruits (colonies <5 cm in diameter) using randomly placed quadrats and transects. Coral recruits were enumerated, measured, and identified to genus. Fourteen genera of corals were observed across all sites and ranged from five to 13 per site. Densities ranged from 6.29 +/- 1.92 (mean +/- SE) to 39.08 +/- 4.53 recruits m(-2), and there were significant site and regional differences in recruit densities. The density of recruits in the upper Keys was significantly lower than in the middle and lower Keys. In addition, the upper Keys were less diverse and had a different recruit size-frequency distribution. The majority of recruits were non-massive scleractinian species that contribute relatively little to overall reef-building processes, a finding that is similar to previous studies. Fewer recruits of massive species were found in the upper Keys compared to the middle and lower Keys. The recruitment patterns of the reefs in the upper Keys could potentially hinder their ability to recover from stress and disturbances