Influence of complexity and habitat heterogeneity on macrofaunal assemblages provided by an invasive ecosystem engineer in Mar Chiquita coastal lagoon

Invasive ecosystem engineers change habitat attributes and species abundance, affecting the structure of invaded communities. In the Mar Chiquita coastal lagoon (37° 40′S, 57° 23°W), the invasive reef-building polychaete Ficopomatus enigmaticus (Fauvel, 1823) generates a heterogeneous environment with habitats of variable complexity: the reefs themselves (high complexity), the sediment surrounding the reefs (low complexity), and the substrate from the areas without reefs (intermediate complexity). Our objective was to compare the macrofaunal assemblages along the whole complexity gradient. We hypothesized that individuals' abundance, diversity, species richness, and evenness of the macrofaunal assemblages increase with habitat complexity, since more complex habitats may represent greater availability of suitable spaces. The composition of the species assemblage was compared through monthly field samplings in each of the three habitats. Results showed that individuals' abundance increased with habitat complexity. In addition, amphipods were the most abundant group in the reefs, while ostracods were the most abundant group in the sediment surrounding the reefs and that from reef-free areas. However, community parameters were occasionally similar between the reefs and the sediment from reef-free areas, depending on the month considered. Our study suggests that the invasion of F. enigmaticus changed the macrofaunal assemblages and the individuals' abundances by providing a high complexity substrate, but also, and less predictably, by increasing habitat heterogeneity, highlighting the importance of including both dimensions of habitat structure in the study of invasions by ecosystem engineers.Fil: Martinez, Lorena E.. Universidad Nacional de Mar del Plata. Facultad de Cs.exactas y Naturales. Instituto de Investigaciones En Sanidad Produccion y Ambiente. - Comision de Investigaciones Cientificas de la Provincia de Buenos Aires. Instituto de Investigaciones En Sanidad Produccion y Ambiente.; ArgentinaFil: Bazterrica, Maria Cielo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Hidalgo, Fernando Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentin