Extreme Freshwater Ecosystems in Patagonia: The Copahue-Agrio System

Abstract

Home Freshwaters and Wetlands of Patagonia Chapter Extreme Freshwater Ecosystems in Patagonia: The Copahue-Agrio System Extreme Freshwater Ecosystems in Patagonia: The Copahue-Agrio System Pedro Temporetti, Gustavo Baffico, Mónica Diaz, Guadalupe Beamud, Daniela Nichela, Juan Cabrera & Fernando Pedrozo Chapter First Online: 30 September 2022 176 Accesses Part of the Natural and Social Sciences of Patagonia book series (NSSP) Abstract This chapter compiles 20 years of research carried out in the River Agrio-Lake Caviahue system by the Water Quality and Aquatic Resources Research Group. This system is characterised by its natural acidity gradient, as well as concentration and transport of nutrients and metals, which results in low species diversity, both in lake plankton and river epilithic communities. Seasonal succession of algal species does not occur in the lake under low (ca. 2.5) pH conditions. Low pH allows most elements present to remain in solution, conditioning environments with high content of metals and phosphorus in the Upper River Agrio section and Lake Caviahue. In recent years, the lake has experienced a significant increase of at least 1 pH unit (a situation controlled by magmatic activity), causing changes in chemical composition. If the increase continues, it is expected to affect epilithic and phytoplanktonic compositions. This fact is unprecedented for aquatic environments in Argentina. The chapter covers (a) basic aspects such as water chemistry, nutrient loadings, trophic status, phytoplankton and epilithic algal communities, geochemistry of sediments and their role in metal and nutrient dynamics and (b) applied aspects such as the use of acidophilic algae as indicators of remediation processes of soils contaminated by hydrocarbons and the behaviour of a naturally acidic lake as a Fenton reactor. The River Agrio-Lake Caviahue system has distinctive characteristics that make it unique in South America. This stresses the importance to preserve it in order to carry out research on processes impossible to observe in other water bodies.