Influence of Macrophyte Complexity and Environmental Variables on Macroinvertebrate Assemblages Across a Subtropical Wetland System

Abstract

Different architectures in aquatic plants with different levels of morphological complexity provide environmental heterogeneity in freshwater ecosystems, and consequently influence invertebrate assemblages. We investigated the relative importance of the structural complexity of macrophytes and environmental variables on the abundance and richness of the macroinvertebrate assemblages associated with aquatic plants across the Esteros del Iberá. This protected wetland system located in Corrientes (Argentina) is fed by rain. Macrophyte habitat complexity was quantified by measuring fractal geometry dimensions of area and perimeter and plant biomass. We sampled macroinvertebrates associated with five species of macrophyte (Egeria najas, Cabomba caroliniana, Potamogeton gayi, Eichhornia azurea and Salvinia biloba) in five shallow lakes during two different seasons (dry and rainy) between 2007 and 2008. Regression analyses revealed that macrophyte structural complexity was an important factor on macroinvertebrate assemblages, whereas explanatory power of environmental variables was low. In both seasons, the fractal dimension of area was the variable with the highest explanatory power on richness, and plant biomass was in the case of macroinvertebrate abundance. To conserve macroinvertebrate diversity in Esteros del Iberá, it would be necessary to maintain the natural heterogeneity indicated by the different structural complexities of the macrophytes across the wetland.