Limnetica 33

The marshes of Doñana (SW, Spain) are some of the largest and best preserved Mediterranean marsh areas represented in Western Europe. They are considered a hotspot of biodiversity, and as such receive protected-area status under two different systems of protected-area management. The importance of submerged macrophytes in the functioning of marsh ecosystems has been addressed in several studies. However, most of the animal biodiversity studies have been developed for vertebrates. Thus, the aims of this study are i) to assess the composition of the invertebrate community in the marsh of Doñana (zooplankton and zoobenthos) in a set of sites representing the different habitats of the marsh in both clear and turbid water states; ii) to compare diversity among patches in different states (clear vs turbid water); and iii) to address the main environmental factors that have influenced their community structure and diversity. A total of 102 taxa were recorded. The highest abundance values were attained by cladocerans and ostracods, both microcrustaceans, and by dipteran insects. It was possible to distinguish different marsh environments characterised by patches of clear water, where the macrophyte beds contribute to an increase of the structural heterogeneity of the marsh, providing the invertebrates with shelter and food resources and subsequently influencing different invertebrate assemblages. Conductivity, soluble reactive phosphorus and chlorophyll-a concentration were the environmental variables that influenced the presence of turbid patches, which showed lower macrophyte cover, diversity and richness values than those seen in the clear water patches. The relationship between diversity (H’) and richness (S), suggested that processes related to species migration (i.e., hydrologic connection with other water bodies, flood duration, and dissemination of propagules) are the main constraints influencing the invertebrate community structure in the Doñana marshes.