The invasive freshwater bivalve Limnoperna fortunei in South America: multiannual changes in its predation and effects on associated benthic invertebrates

Abstract

The invasive golden mussel Limnoperna fortunei is known to strongly affect benthic communities in South American freshwaters, but the evolution of these effects after the early invasion stages is poorly understood. Using predator exclusion (covered with 15- and 40-mm meshes) and inclusion (unprotected) substrates, we investigated the interaction between golden mussels and benthic invertebrate communities at different levels of exposure to predators in the Parana River delta. Colonization of the substrates was largely dominated by the mussels. Oligochaeta, Nematoda, and Hirudinea were the most abundant accompanying groups, while Rotifera, Tardigrada, Copepoda, Cladocera, Chironomidae, Gastropoda, Hydracarina, Amphipoda, and nauplii appeared sporadically. Regardless of their different trophic modes and functional attributes, the numbers and biomass of associated invertebrates were not only enhanced by protection against predators, but also by the presence of mussel colonies. Enhancement of invertebrate densities associated with mussel colonies was higher on unprotected than protected substrates, suggesting that invertebrate facilitation increases with increasing predation pressure. Comparisons with a similar study carried out a decade earlier suggest that, after two decades of invasion, the reproductive potential of the mussel, the predation pressure on its colonies, and its facilitation effects on other invertebrates have increased in the Parana River delta.