Abstract Terrestrial runoff is a source of sediments and nutrients to coral reefs. Due to runoff, Brazilian reefs are typically turbid, and have coral species that are naturally turbidity-resistant. This study investigated how terrestrial input influences population and physiology for the coral Favia gravida on two reefs with differences in river mouth proximity in eastern Brazil. The population structure and physiological traits of F. gravida colonies were assessed on both reefs, then some colonies selected for a subsequent transplantation experiment. The reef less impacted by terrestrial influence showed higher population density and lower recruitment. At this site, the coral colonies displayed higher calcification and larger larvae. The reproductive effort between coral populations at the two sites showed no significant difference. The transplantation experiment confirmed the high physiological plasticity of F. gravida colonies at the more turbid reef site. Despite being regarded as a more challenging environment, where F. gravida has a lower population density, the reef closer to the river mouth appears to secure more nutrients, which may heterotrophically compensate its coral colonies.

A sedimentação tem sido considerada uma importante fonte de impacto nos recifes de coral. Uma comparação entre as taxas de sedimentação, teor de carbonatos nos sedimentos, cobertura coralínea e tamanho de colônias de corais para as espécies mais comuns (Mussismilia braziliensis, Siderastrea stellata, e Favia gravida) foi realizada em 3 locais no Banco dos Abrolhos. Os locais representam um gradiente de distância da costa: Pedra de Leste (14 km), Pontas Sul (26 km) e Parcel dos Abrolhos (58 km). A sedimentação foi maior no inverno (p <0,05), mas não foi observada diferença entre os locais. O tipo de sedimento diferiu entre locais (P <0,05), sendo que Parcel dos Abrolhos apresentou 90% de carbonatos, Pontas Sul 65% e Pedra de Leste 50%. A cobertura coralínea foi maior no local mais afastado de terra (p <0,01), onde a cobertura de zoantídeos foi menor. Diferenças de tamanho de colônias foram encontradas apenas para M. braziliensis, com menores colônias em Pedra de Leste (p <0,05). A distribuição dos sedimentos terrígenos e a turbidez devem ser os principais fatores controladores do desenvolvimento dos recifes de Abrolhos.

Sedimentation has previously been considered an important source of impact in coral reefs. We compared 3 sites on the Abrolhos Bank, Brazil, regarding sedimentation rates, carbonate sediment composition, coral cover, and colony size for the commonest local coral species (Mussismilia braziliensis, Siderastrea stellata, and Favia gravida). The sites are located at different distances from the mainland: Pedra de Leste (14 km), Pontas Sul (26 km), and Parcel dos Abrolhos (58 km). Sedimentation was higher in winter (p <0.05), but no difference among sites was noted. Sites differed in sediment type (P <0.05), with Parcel dos Abrolhos showing nearly 90% of carbonate in sediment composition, Pontas Sul nearly 65%, and Pedra de Leste only nearly 50%. The farther from the mainland, where the zoanthid cover was smaller, the higher was the coral cover (p <0.01). Differences in colony sizes were found only for M. braziliensis, with smaller colonies occurring at Pedra de Leste (p <0.05). It is suggested that terrigenous sediment distribution and turbidity may be the main factors controlling reef development at the Abrolhos Reefs.

Se hizo el primer estudio de coexistencia de organismos bénticos de arrecifes brasileños en tres localidades del Archipiélago de Abrolhos, registrando la presencia de organismos en círculos de 10 y 20 cm de diametro, distribuidos al azar en transectos. La mayoría de los organismo frecuentes (algas coralinas macizas y ramificadas, Favia gravida y Agaricia agaricites) mostraron la más alta "coexistencia positiva", tal vez por su abundancia. El coral más frecuente (Siderastrea stellata), sin embargo, mostró apenas algunos eventos de coexistencia significativos (9% de 32 ensayos). Debido a que la mayor parte de los eventos fue positiva, y considerando que existe una alta variabilidad en las interacciones significativas en diferentes localidades, las comunidades bénticas del Archipiélago de Abrolhos pueden haber sido estructuradas principalmente por factores abióticos, mas que por factores bióticos.

The first study on coexistence of reef benthic organisms in Brazilian coral reefs was done in three localities of the Abrolhos Archipelago. Organisms were recorded in concentric circle samples (10 and 20 cm in diameter) randomly laid on transects. Type and frequency of "coexistence events" between pairs of organisms were determined. Most frequent organisms (massive and branched coralline algae, Favia gravida, and Agaricia agaricites) also had many significant positive coexistence events. These results might be related to the abundances of these organisms. The most frequent coral (Siderastrea stellata), however, exhibited only a few significant coexistence events (9% of 32 tests). Since the great majority of events were positive, and since there was high variation in the species/groups involved in significant events in different localities, benthic communities of Abrolhos Archipelago may well be structured primarily by abiotic rather than biotic factors.