Molluscan assemblages on artificial structures: a bioinvasion perspective from Northeast Brazilian ports

As the impact of coastal development impinge on our natural ecosystem, we are increasingly compelled to study the effects of artificial habitats on the distribution and abundance of marine species. In particular, understanding how physical factors can influence distributional patterns of benthic communities along artificial structures built in ports that create possibilities for a variety of non-indigenous species (NIS) occur. This paper aims to compare the distribution of mollusc's assemblage along environmental factors known to influence the distribution of epibenthic species: depth, shading and locality features such as distance from shore and period of submersion of artificial structures. Molluscan assemblages were examined over a depth gradient extending from middle intertidal (0 m) to shallow subtidal (5 m). We also assessed and compared the distribution of Eualetes tulipa (established) and Isognomon bicolor (invasive) in two port locations at Northeast coast of Brazil. A total of 33 native species, 7 cryptogenic and two NIS were found. The most abundant was a native species, Crassostrea brasiliana, followed by the NIS I. bicolor and E. tulipa, respectively. Using PERMANOVA: depth gradient, locality and interaction between these fixed factors showed significant effects on the vertical distribution along the artificial structures sampled. Results suggest that recent substrata availability supports the colonization of NIS species and that these, in areas with more stable communities, cohabit with and are regulated by native species. Furthermore, this is the first study discussing the distribution of the established NIS vermetid E. tulipa in Northeast Brazilian coast.