Small-scale differences in tropical subtidal rocky reef communities of Floreana Island, Galápagos

Abstract

Tropical subtidal rocky reef communities are less prominent than coral reefs and characterized by macroalgae, mobile invertebrates, reef fish and diverse communities of epibenthic invertebrates. In the Galápagos Marine Reserve, more than 80% of the shallow benthic habitats are rocky lava reefs. In order to examine the effects of small-scale differences in oceanographic regimes, two rocky reef study sites, an upwelling and a non-upwelling site, were chosen off Floreana Island. The benthic community structure of the sites was studied for two years by subtidal monitoring. Simultaneously, benthic succession studies and grazer exclusion experiments were conducted at both sites. Further, the food web structure for Floreana Island was analyzed by using the stable isotope approach.Results revealed significant differences between both study sites. These findings reflect the particular oceanographic setting of the Galápagos Archipelago and that Floreana Island may also represent a model system to investigate ecological responses along abiotic gradients.