Influência da complexidade do habitat e da sazonalidade sobre a fauna associada a macroalgas de um manguezal hipersalino

Abstract

Mangroves have a mosaic of different habitats and microhabitats, each with their specific levels of complexity and occupied by different kinds of organisms. In this context, the present study aimed to assess the effect of habitat complexity and seasonality in the composition and structure of the invertebrate macrofauna associated with macroalgal species with different morphological characteristics. The research was conducted in the hypersaline mangrove of Tubarão River (5 o 04'34.87"S, 36 o 27'32.36"W), municipality of Macau, northern coast of the state of Rio Grande do Norte, Northeastern Brazil. Aiming to analyze the effect of habitat complexity on a local microhabitat scale and considering that the studied mangrove, due to their peculiar hipersalinity characteristics may harbor a rich fauna and flora, the following questions guide this research: a) Does the different macroalgae studied have different degree of habitat complexity? b) Macroalgae with different morphological characteristics supports invertebrate communities significantly different? c) Is there a relationship between habitat complexity and the composition, abundance and diversity of the invertebrate community of their phytal? and d) Is there difference between the pattern of abundance and composition of invertebrates found in macroalgal species between the dry and rainy seasons? A total of 1,750 individuals classified into five taxa were collected: Echinodermata, Amphipoda, Mollusca, Isopoda and Polychaeta, with 723 individuals found in the rainy season (associated with Gracilaria sp.) and 1,028 in the dry season (430 in Dictyota sp. and 598 in Solieria filiformes). Macroalgae of the dry period were morphologically distinct, however, the invertebrate fauna were not significantly different (p=0.1037), thus reinforcing that seasonality may have influenced the abundance and composition of macroinvertebrate taxa. The different macroalgae showed distinct morphological patterns and different degrees of habitat complexity, where more complex algae harbored a richer, abundant and diverse mollusc fauna. Specifically in the case of molluscs, species composition was typically marine, higher than other mangrove environments. Furthermore, the malacofauna was predominantly composed by micromolluscs, as adults whose sizes do not exceed 10 mm, and young individuals of species that reach a larger size. It is suggested that both habitat complexity as well as seasonality affect the richness, diversity and abundance of associated communities. In general, the marine macroalgae provides support for a variety of marine taxa, and may play an important role in increasing the structural underwater habitat complexity of mangrove systems.