The Role of Sediments and Phosphorus in the Evaluation of Water Resources Quality in Patagonia

Abstract

Among the processes of anthropogenic contamination of aquatic environments, eutrophication is one of the most studied. Phosphorus is a key nutrient in eutrophication and, in many cases, the limiting nutrient in various water bodies. Furthermore, sediments from an aquatic environment can be considered as an “environmental information bank”. They play an important role in the nutrient cycle in lakes since nutrients are transported to the bottom by sedimentation and can return to the water column by various mechanisms which are sometimes extremely complex. The aim of this chapter is to summarize 30 years of research carried out by the Water Quality Group (INIBIOMA, CONICET-UNComahue) on sediments from several lake environments in Argentinian Patagonia and their role in aquatic resource assessment. A total of 11 water bodies in the region were analyzed, considering different physical and chemical parameters, always applying the same methodology (in field and laboratory). The results show that (1) pH is one of the main parameters that influence the P exchange between sediments and the water column; (2) texture, chemical composition, and mineralogy are essential to understand sediment genesis and transport mechanisms; (3) three gradients determine the distribution of the studied environments: (a) North–South geographic gradient, (b) pH gradient and (c) trophic gradient; (4) the use of sediment bioassays with native algae is a particularly useful tool for rapidly evaluating the anthropic impact on water bodies; and (5) sediment studies allow obtaining information on, for example, contaminated and uncontaminated areas and distribution patterns of contaminants, and should be included in monitoring programs.