The relationship between physical and biological habitat conditions and hermatypic coral recruits abundance within insular reefs (Colombian Caribbean)

Little evidence exists on the dependence between the presence and abundance of juvenile hermatypic corals and the conditions of their habitats, despite that juveniles contribute with the understanding of the community structure and its reproductive success. To assess this, the abundance of nine species of juvenile corals was correlated with eight macro-habitat (location of the reef on shelf, depth) and micro-habitat (type and inclination of the substrate, exposure to light, texture and amount of sediment accumulated on bottom, potential growth area for juveniles) conditions. Sampling was conducted in four insular coral reefs in the Colombian Caribbean: two oceanic and two continental reefs (influenced by large rivers), covering a total of 600m2 and the distribution of corals on a vertical gradient. Contingency tables and coefficients (magnitude) and multiple correspondence analyses were used to evaluate the dependency ratios for each species. The results showed that Agaricia tenuifolia displayed the most robust pattern of dependence (two high and two moderate), significant for juveniles present at a high frequency in continental reefs, devoid of potential area for juvenile growth (surrounded by macroalgae), and covering horizontal substrates exposed to light. The juveniles were associated with a habitat of moderate to high bottom accumulation of extremely fine sediment. Porites astreoides presented four moderate dependencies; ocean reefs between 2-16m depths, a high frequency of juveniles on horizontal substrates, exposed to light, non-sedimented and occupied by competitors. Siderastrea siderea displayed three moderate dependences for juveniles in cryptic zones, inclined substrate and devoid of competitors. A. lamarcki, Leptoseris cucullata and A. agaricites presented two moderate dependences; these species share high abundance of juveniles in habitats with no sediment, exposed to light and occupied by competitors (except A. agaricites). The P. porites, Favia fragum and Montastraea cavernosa species had a moderate dependence with high incidence of juveniles in ocean reefs and microhabitats exposed to light. For the nine species, results indicate that the presence (colonization), abundance and survival of juveniles, depend on certain species-specific particularities of the habitat. However, the juveniles show high tolerance and plasticity to a range of habitat variables, given their independence and low dependence observed in over 50% of the variables assessed.

Existe poca evidencia sobre la dependencia entre la abundancia de juveniles de corales hermatípicos y las condiciones del hábitat. La abundancia de corales juveniles se relacionó con condiciones del hábitat a macro (ubicación del arrecife, profundidad) y microescala (tipo e inclinación del sustrato, exposición a luz, textura y cantidad de sedimento, área de crecimiento potenial de juveniles). El muestreo se realizó en cuatro arrecifes insulares del Caribe colombiano. La dependencia se evaluó usando tablas y coeficientes de contingencia y análisis de correspondencias múltiples. Agaricia tenuifolia mostró las dependencias más robustas, siendo significativas para juveniles presentes frecuentemente en arrecifes continentales, sustrato horizontal expuesto a luz, con competidores. Los juveniles se asociaron con moderado a alto sedimento muy fino acumulado en el fondo. Porites astreoides presentó cuatro dependencias; alta frecuencia en sustrato expuesto a luz, horizontal, sin sedimento, con competidores y en arrecifes oceánicos entre 2-16m. Siderastrea siderea exhibió tres dependencias, para juveniles en lugares crípticos, sustrato inclinado y sin competidores. A. lamarcki, Leptoseris cucullata, A. agaricites, P. porites, Favia fragum y Montastraea cavernosa mostraron el menor número de dependencias, compartiendo alta frecuencia en hábitats sin sedimento, expuestos a luz, con competidores y en arrecifes oceánicos. Los resultados sugieren que la abundancia y sobrevivencia de juveniles dependen de ciertas particularidades especie-específicas del hábitat; sin embargo, los juveniles presentan tolerancia a una amplia gama de variables del hábitat.

Skeletal variability of the coral Favia gravida (Verrill, 1868) from Brazil / Variabilidade esquelética do coral Favia gravida (Verrill, 1868) do Brasil

The skeletal variability of the coral Favia gravida, a species endemic to Brazil, was quantitatively described including populations from three locations: Tamandaré (state of Pernambuco), Abrolhos (state of Bahia), and Santa Cruz (state of Espírito Santo). Ten colonies were collected from each population and fourteen morphological characters were measured from ten corallites per colony. The results of univariate (among 14 skeletal characters, 7 showed p < 0.05) analysis provide evidence to suggest that F. gravida has considerable morphological plasticity, which may explain its ability to adapt to different ecological conditions. The species also displays polymorphism within and between colonies of each population. Intercolony variation within populations was relevant for most of the variables measured. Canonical discriminant analysis (r = 0.8648) showed that the population farthest offshore (Abrolhos) was distinct from the other two (Tamandaré and Santa Cruz), which have been affected by terrigenous sediments carried from the coast. Specimens from Santa Cruz displayed the highest degree of meandrinization.

A variação do esqueleto do coral Favia gravida, uma espécie endêmica do Brasil, foi descrita quantativamente a partir de populações de três localidades, incluindo Tamandaré (Estado de Pernambuco), Abrolhos (Estado da Bahia) e Santa Cruz (Estado do Espírito Santo). Dez colônias foram coletadas de cada população e quatorze caracteres morfológicos foram medidos de dez coralitos por colônia. Os resultados da análise univariada (dentre os 14 caracteres esqueléticos, sete apresentaram p < 0,05) fornecem evidências que sugerem que F. gravida tem uma plasticidade morfológica considerável, o que pode explicar sua habilidade para se adaptar às condições ecológicas diferentes. A espécie demonstra, também, polimorfismo dentro e entre as colônias de cada população. A variação intercolonial dentro de populações foi, também, marcante para a maioria das variáveis medidas. A análise discriminante canônica (r = 0,8648) mostrou que a população mais distante da costa (Abrolhos) foi distinta das outras duas (Tamandaré e Santa Cruz), as quais estão sendo afetadas por sedimentos terrígenos provenientes da costa. Os espécimes de Santa Cruz demonstraram o mais alto grau de meandrinização.