Macronutrient retention in Cerrado streams (SP) and its relationships with aquatic metabolism along gradients of environmental conditions: an ecosystem services' approach

Abstract

Aquatic ecosystems are responsible for key ecosystem services and provide direct and indirect benefits to the society. The nutrient retention in surface waters, which is associated to physical, chemical and biological processes, is one of their main functions and it is influenced by anthropogenic interferences. Nutrient retention has been mostly studied in temperate environments, but little is known about how the environmental characteristics of tropical systems and human impacts affect nutrient uptake kinetics. The main objective of this research is to estimate the macronutrients retention in streams located in the Cerrado savanna (São Paulo, Brazil) and correlate this process to stream ecosystem metabolism and other key aspects. In addition to the physical and chemical characteristics, we will estimate nitrate, ammonium and phosphate retention rates in different reaches of five streams, characterized by gradients in environmental conditions to test hypotheses related to land impacts on stream nutrient retention. These data will be related to metabolism estimates (respiration, gross and net primary production), which will be modeled using stream in situ dissolved oxygen variation. We will also investigate the composition of stream biofilms through biochemical indicators and elemental analysis to determine the role of microrganisms in nitrogen and phosphorus retention. In addition to technological advance, through the use of methodologies not commonly applied in tropical environments (e.g, Trace Addition for Spiraling Curve Characterization), we expect that the results will contribute to different areas of knowledge (Engineering, Biology and Environmental Management). This will be achieved through the identification of the most important drivers of the role of the streams are sinks or sources of macronutrients. The research team is comprised of members from the University of São Paulo, Federal University of São João del-Rei and Kansas State University. At least five graduate students (masters and doctorate) and two undergraduate students will perform their thesis studies in this project. In addition to promoting international collaboration, as the project involves a North-American institution, papers will be published in peer-reviewed journals. (AU)