Benthic communities on hard substrates covered by <i>Limnoperna fortunei</i> Dunker (Bivalvia, Mytilidae) at an estuarine beach (Río de la Plata, Argentina)

The structure and composition of benthic communities on hard substrates covered by the nonindigenous bivalve <i>Limnoperna fortunei</i> Dunker, the golden mussel, were quantified in the middle zone of the Río de la Plata Estuary (Argentina) from April 2001 through March 2002. A total of 26 taxa were recorded. <i>L. fortunei</i> and Nematoda were the central and dominant groups, with a prodigious abundance of over 80%. The prevalence of <i>L. fortunei</i>, rather than the environmental variables, regulated the dynamics of the associated invertebrate fauna. The golden mussel alters both the structure and function of benthic native communities on hard substrates, allows a higher surface available for colonization and refuge, and provides food source to deposit-feeding organisms in the form of organic or residual material. The mussel also increases the abundance and diversity of taxa on hard substrata - such as Oligochaeta, Hirudinea, Tardigrada, Chironomidae, Copepoda, Tanaidacea, and Hydrachnidia. Similarities and nonparametric multidimensional-scaling analyses indicated that the benthic composition had a seasonal variation. <i>L. fortunei</i> has an environmental impact, an ability to invade new freshwater ambiences worldwide and ecological characteristic comparable to those of <i>Dreissena polymorpha</i> Pallas (the zebra mussel) of North America and Europe. Facultad de Ciencias Naturales y Museo