Plankton as an Evaluation Tool for Ecosystem Conservation: A Study Involving Different Habitats Associated With the Salado River in the Pampa Region of Argentina

Freshwater biodiversity is declining sharply. The conservation of these biodiverse habitats has generally depended on their designation as protected areas, but specific groups such as plankton tend to be overlooked. The Salado River (Argentina) constitutes a highly characteristic morphologic feature of the pampas, having a basin of 150,000 km². The Las Flores system, particularly, is key in the development of the river, and the presence of two tributaries adds landscape heterogeneity with habitats such as shallow lakes, backwater ponds and wetlands. Our aim in this work was thus to evaluate the Salado River conservation status by measuring the specific richness of its planktonic community in order to argue for the Salado's establishment as a protected reserve. An analysis of the phytoplankton and zooplankton assemblages after several years of sampling in the river, streams and backwater ponds indicated that habitat heterogeneity increased the diversity of the region and that sites such as backwater ponds or streams were critical for the functioning of the river system as a whole through adding particular species or acting as species reservoirs. This supports habitat fragmentation in the area, which combined with environmental heterogeneity contributed to high ß diversity values. However, such separation also involves a trade-off because prolonged isolation between subsystems can result in net species loss. Finally, the present work focused on the significance of biodiversity at the landscape level, with planktons as a model for the conservation of a principal site in one of the main rivers of Argentina.