Chemical diversity and spatial variability in myriad lakes in Nhecolândia in the Pantanal wetlands of Brazil

• Grant number: 13/22272-2
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: December 01, 2013
• End date: May 31, 2014
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Physical Geography
• Principal Investigator: Sonia Maria Furian
• Grantee: Sonia Maria Furian
• Host Institution: Faculdade de Filosofia, Letras e Ciências Humanas (FFLCH). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• City of the host institution: São Paulo

Abstract

Nearly 15,000 shallow, saline, or freshwater lakes and ponds coexist in close proximity in the Nhecolândia, a 24,000 km² subregion of the Pantanal wetland in Brazil. This study aims to understand the origin of such diversity in surface water, which is a key aspect for the wetland services and biodiversity in the region. Both soil observations and water samples were collected at the regional or local scale and supplemented by previously published datasets. Statistical and geostatistical treatments were carried out, and completed by discrete water table monitoring. The results confirmed the absence of a regional pattern in surface water salinity, and the independence of electrical conductivity values, even for neighboring lakes. Despite great differences in chemical composition, all surface waters in the region belong to the same chemical family, corresponding to several concentration stages of the Taquari River water that supplies the region. The concentration stage depends on the hydrological functioning of each lake, which is itself controlled by the relative importance of low permeability soils as a barrier to movement of water into or out of the lakes through the sub surface. In this framework, oligosaline ponds, freshwater lakes, and saline lakes work as recharge-, flow through-, and discharge-wetlands, respectively. The salinity observed in some lakes results from an ongoing process of accumulation and evaporation under relatively humid climatic conditions and poor drainage. (AU)