Recifes de arenito entremarés na zona tropical: Um ecossistema com alta heterogeneidade espacial e temporal?

Abstract

In the reef ecosystems of the intermarine region there are various biotic and abiotic components, where benthic communities are organized and structured creating a heterogeneity, one which may vary in space and time. These environments function as habitats with intermediate diversity between coral reefs (higher) and rocky costs (lower), but there is a dearth of studies that evaluate this variability. Thus, the objective of this study is to evaluate spatial and temporal heterogeneity in an intertidal zone environment through the use of ecological (benthic community coverage) and sedimentological (particle size, chemical carbonate and organic material) indicators that act as systems. The results show that the groups of macroalgae and filamentous algae were dominant during most of the study period, except for August/2019, with low coverage of the former (1,29%) and high coverage of the latter (37,29%). Common feature displayed has high coverage rates ranging from ~ 24% to 41%. Coral and zoanthids charge coverage rates of less than 15% of reef coverage every month. Among the species, Palythoa variabilis was more abundant, ranging from 7,5% to 10,83%. The sediment on sandstone recovery is mainly composed of fine sand. There was variability in particle size composition between months, a factor related to the beginning and end of the rainy season. The hydrodynamic conditions in the study area, combined with the continental maximum during the rainy season, had a direct impact on the distribution of benthic community organisms. The organic matter content favored a high occurrence of filamentous algae in August/2019. Palythoa variabilis presented a great resistance to desiccation, occurring in areas with longer exposure time and presence of unconsolidated material. Palythoa caribaeorum and Zoanthus sociatus presented low occurrence due to their vertical, considering a three-dimensional recovery, a factor not addressed in the methodology. It was concluded that there was significant heterogeneity both spatially (on a scale of few meters) and temporal (over a few months). This heterogeneity was determined by physical factors (presence of shoals, irregular rocks, tidal intrusion), as well as interspecific relations (algae and corals). Research on this type of coastal environment can be used to assess impacts on reef ecosystems worldwide, making predictions of future conditions regarding the distribution of the benthic community.