Comunidade de peixes nas piscinas de maré do Atol das Rocas, Brasil : a influência da conexão com o mar

Abstract

The reef environments have the highest species diversity among marine ecosystems. The reef fish communities are characterized by their high diversity, both in terms of numbers of species as in morphology and are important components of the biota of these environments, working in the structuring of communities through predation and competition processes. The structure of fish populations respond to various environmental factors (rainfall regime, environmental geomorphology, tidal dynamics, water transparency, quality and type of organic matter, current velocity and availability of food resources), these factors influence the spatial distribution and temporal species. Thus, this aimed to understand the timeline distribution of fish populations between the pools with or without connection to the open sea in Rocas Atoll, identifying the environmental characteristics with the greatest influence on the structure of fish populations. This is the only atoll in the South Atlantic Ocean and is located 266 km off the Brazilian coast, differs from other atolls because it is composed exclusively of algae encrusting coralline. In its plateau occur tidal pools, canals and sandy islands. 90 hours of diving were held in two pools with connection to the open sea and two disjoint through five linearly arranged transects the edge to the center of the pool, including the dry and rainy seasons. The temperature data were recorded, salinity, pH and dissolved oxygen from each pool much water in the dry season and the rainy. It was identified to the substrate composition of the pools through the photos using the methodology Coral Point Count with Excel Extensions program. 12,065 individuals, distributed in 20 families and 33 species were observed. The pools with connection with the sea showed the highest values of diversity and abundance and presented as the most abundant species Thalassoma noronhanum, Acanthurus chirurgus, Abudefduf saxatilis and Stegastes rocacensis, these species are equivalent to 87.3% of relative abundance these pools. The pools without connection with the sea showed a difference in the fish community in comparison to the pools with connection, being the most abundant species the A.saxatilis, A. chirurgus, T. noronhanum and Haemulon chrysargyreum. The richness, diversity and equitability varied between climatic periods and connection type. A significant correlation between the diversity and depth (RS 0,322e = p <0.05) was observed. They were observed seven types of substrate: coral, zoanthid, turf algae, seaweed, corallinae algae, gravel and sand. The substrate showed a correlation between the two pools open with rS = 0.857, p <0.05 where both presented seaweed as most of the substrate. In Rocas Atoll the connection type and depth of the pool, time of year and the type of substrate influence the composition and distribution of fish populations between the pools.