Differences in the macrozoobenthic fauna colonising empty bivalve shells before and after invasion by Corbicula fluminea

Bivalve shells can potentially alter the structure of aquatic benthic communities. However, little is known about the effect that different shell morphologies have on their associated fauna. This study aimed to understand how empty shells, from four different freshwater bivalve species, affect macrozoobenthic communities, using the River Minho (Iberian Peninsula) as a study area. Three native (Anodonta anatina, Potomida littoralis, Unio delphinus) and one non-indigenous (Corbicula fluminea) species were used for this research. Comparisons among species and between scenarios (i.e. before and after invasion by C. fluminea) were performed. Our results suggest that macrozoobenthic community structure did not vary among treatments, with the exception of species richness, which was higher on shells of native species. Furthermore, little difference was detected when comparing scenarios with and without C. fluminea shells, despite dissimilarities in size and morphology between species. The empty shells of C. fluminea partially (in terms of density and biomass, but not in species richness) replaced the role of empty shells of native species as a physical substratum for the associated macrozoobenthic community.Martina Ilarri is supported by a Post-doc grant (SFRH/BPD/90088/2012) from the Portuguese Foundation for Science and Technology – FCT through POPH/FSE funds. This study was conducted within the scope of the project ECO-IAS: Ecosystem-level impacts of an invasive alien species, supported by FCT and COMPETE funds (contract: PTDC/AAC-AMB/116685/2010) and was also partially supported by the European Regional Development Fund (ERDF) through COMPETE funds (PEst-C/MAR/LA0015/2011) and by FCT/MEC through Portuguese funds (PIDDAC – PEst-OE/BIA/UI4050/2014).info:eu-repo/semantics/publishedVersio

Unravelling the complex structure of a benthic community: a multiscale-multianalytical approach to an estuarine sandflat

We evaluated scale-dependent patterns of distribution of sandflat macroinfauna of a coastal lagoon, using different analytical approaches. Thesampled area was divided into three sectors (outer, north-inner, south-inner) containing small promontories. At each side of the promontories wedefined stations in a line transect across the sandflat. Thus, we evaluated sediment characteristics and macroinfaunal responses to sectors,orientations and intertidal levels; animalesediment relationships were also studied. At a large scale, there was a clear pattern of sedimentcomposition and macroinfaunal abundance. While the outer sector had medium to coarse sands, reflecting the high hydrodynamic conditions existingnear the lagoon entrance, the inner sectors showed sandy and muddy sediments. Most species were in low abundances at the outer sector. Atsmall scale, macroinfaunal abundance and species richness decreased sharply towards the upper sandflat level. Also at small scale, sediment compositionlimited the maximal densities reached by all species, with exception of the deposit-feeding polychaetes. Thus, the macroinfaunal communityat muddy sediments was dominated by burrowing deposit-feeders, while all species peaked in sandy sediments. Our results suggestthat physical factors shaping macroinfaunal communities operate at different scales and are better detected using several analytical approaches.Large scale patterns, associated with along-shore variations in disturbance by currents, were detected as changes in the mean abundance of macroinfauna.Small scale patterns related to sediment characteristics were observed as changes in maximal densities of macroinfauna. Small scale patterns,associated with the level of inundation of the sandflats, were detected through changes in the abundance and presence of macroinfauna. Theevaluation of the role of the physical conditions on communities must involve the use of several sampling and analytical approaches