Invertebrados bentônicos de recifes areníticos tropicais: avaliação de métodos e estruturação da comunidade intertidal

Abstract

Rocky intertidal environments are important feeding, growth and reproduction areas to a variety of benthic organisms. These ecosystems can be found worldwide and their benthos’ composition and temporal and spatial patterns are influenced by environmental and biological factors. Most studies on these environments have focused on rocky shores of temperate and subtropical regions. On the other hand, there is a lack of studies in other rocky formations and tropical regions, specially testing proper methodologies that are suitable for greater substrate heterogeneity and lower slope. This study had three main objectives: 1) to identify the main types of method used for quantifying benthonic organisms, using scientometric analysis; and, in tropical sedimentary reefs: 2) to test random and stratified quadrats and transects with quadrats to test the survey method that best represent richness of molluscs and echinoderms in these environments; 3) and, after determining the most suitable survey method, to test which environmental factors influence occurrence, abundance and richness of these organisms, and test whether there is seasonal variation of abundance of taxa. The organisms’ mobility was one of the determinant factors when choosing benthonic survey method in the analyzed papers. Quadrats and transects with quadrats were the main methods used to delimit areas for counting of mobile individuals and estimation of sessile cover. On the selected tropical reefs for the methodological tests, random transects with quadrats showed better richness results with less sampling effort, including sampling under boulders when they were present. Substrate cover, reef typology, habitat complexity and exposure time were the main environmental factors determining the structure of communities over the reefs. Substrate cover, habitat complexity and exposure time were the main factors structuring communities under boulders. Regarding organisms’ abundance between the different seasons, Pugilina tupiniquim, Holothuria grisea and Cerithium sp were indicative taxa of the rainy season and Aplysia dactylomela was indicative taxa of the dry season in sheltered reefs with rocky blocks.