Connectivity as the control key to intensity of flood pulse in Taquari River oxbow lakes

Abstract

The Taquari River is one of the most important tributaries of the Paraguay River, whose sediments are carried and deposited on the plain forming the largest alluvial fan in the world, known as Pantanal. In the floodplain, the course of the river has been modified by the sedimentation process, resulting in lakes with different degrees of connectivity with the river. This study assessed the influence of connectivity on the physical and chemical characteristics of water along a hydrological cycle in oxbow lakes of the Taquari River floodplain, in Mato Grosso do Sul, Brazil. Sampling was carried out monthly, from May 2005 to June 2006.The physical and chemical data of the water and the variables of river level and rainfall intensity were correlated by Principal Component Analysis (PCA). Limnological differences resulted from distinct degrees of connectivity between the oxbow lakes and the Taquari River. Variations in the dry and rainy seasons established a gradient that extends over a space-time continuum and generates greater environmental heterogeneity and, consequently, greater biodiversity. Thus we conclude that this mosaic of lakes and the surrounding landscape requires protection and preservation because of its importance for biodiversity conservation.

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“…Aquatic primary productivity is often limited by either the availability of nitrogen or phosphorus, or co-limited by both nutrients (Guildford and Hecky, 2000), and in floodplains external nutrient supply determines overall ecosystem productivity. As a result, floodplain lands subject to flooding only by relatively nutrientpoor local rainfall tend to be markedly less productive than those inundated by nutrient-rich river water from the upland tributaries (Junk et al, 1989(Junk et al, , 2011Lewis et al, 2000;Hamilton, 2002;Güntzel et al, 2020).…”