Effects of the invasive clam Corbicula fluminea (Muller, 1774) on a representative macrobenthic community from two estuaries at different stages of invasion

The introduction of non-indigenous species (NIS) is one of the main reasons for the loss of biodiversity worldwide. This phenomenon has increased dramatically in recent decades leading to a reduction of the availability of ecosystem goods and services. One of the most important invasive species in aquatic ecosystems is the Asian clam, Corbicula fluminea (Muller, 1774). In this work, we compared the benthic macroinvertebrate assemblages in the freshwater section of two river estuaries, Lima and Minho, which were invaded with a 12-year gap by this non-indigenous bivalve. This study shows that C. fluminea's presence can model other species' abundance in a strong fashion, especially in the later stages of invasion when it is fully settled. Although our results showed that the abundance of this invasive bivalve is linked to high values of biodiversity and to direct increases in the abundance of Gastropoda, an invasion by C. fluminea seems to prompt negative effects on specific crustacean species, such as the abundant amphipod species Corophium multisetosum. We propose that the dominance of one competitive species, coupled with favourable abiotic factors, may hinder the progress of C. fluminea's invasion.