Facilitation in the low intertidal: effects of an invasive species on the structure of an estuarine macrozoobenthic assemblage

Abstract

The Asian clam Corbicula fluminea (Müller, 1774) has been recognized as one of the
\nmost important invasive alien species in aquatic ecosystems and may have significant ecological
\nand economic impacts. Recently, the presence of C. fluminea was associated with changes in benthic
\nand epibenthic fauna. In this study, we aimed to understand the mechanisms underlying the
\neffects of C. fluminea on an estuarine macrozoobenthic assemblage using a manipulative experiment.
\nWe used 5 different treatments (control, rock, closed, live, open), which were placed in a
\nlow sandy intertidal soft bottom area in the Minho estuary (NW Iberian Peninsula) for 2 months.
\nWe found that the presence of live and open empty shells of C. fluminea had positive effects on
\nthe density, biomass and species richness of macrozoobenthos, specifically on species belonging
\nto Annelida, Mollusca and Crustacea. Our results may be explained by 2 main mechanisms: (1)
\nthe production of feces and pseudofeces by C. fluminea, which increases organic matter content
\nand food resources for some macrozoobenthic species; and (2) ecosystem engineering activities by
\nC. fluminea, which can create conditions for the establishment of other species via shell production
\nand bioturbation in the sediments.