Limnology in the Upper Paraná River floodplain: large-scale spatial and temporal patterns, and the influence of reservoirs

Abstract

Knowledge of abiotic limnological factors is important to monitor changes caused by humans, and to explain the structure and dynamics of populations and communities in a variety of inland water ecosystems. In this study, we used a long term data-set (eight years) collected in 10 habitats with different features (river channels, and connected and isolated lakes) to describe the spatial and temporal patterns of some of the principal limnological factors. In general, the degree of connectivity of the lakes, together with the rivers to which the lakes are connected, were important determinants of their limnological characteristics. These differences are expected, because rivers entering the floodplain come from different geological regions and are subject to different human impacts. At large spatial scales, these differences contribute to the increased habitat diversity of the floodplain and thus to its high biodiversity. With regard to temporal variation, Secchi-disk transparency increased, and total phosphorus decreased in the Paraná River main channel during the last 20 years. Although these changes are directly attributed to the several reservoir cascades located upstream, the closing of the Porto Primavera dam in 1998 enhanced this effect. The increase in water transparency explains biotic changes within the floodplain. The lower-phosphorus Paraná River water probably dilutes concentrations of this element in the floodplain waterbodies during major floods, with future consequences for their productivity.Keywords: floodplain, abiotic factors, temporal and spatial variation, productivity. Limnologia na planície de inundação do Alto Rio Paraná: padrões em amplas escalas espaciais e temporais e influência de reservatórios ResumoFatores limnológicos abióticos têm sido importante para monitorar as mudanças causadas pelo homem e para explicar a estrutura e a dinâmica de populações e comunidades em uma variedade de ecossistemas aquáticos. Neste estudo, foram usados dados de vários anos (oito anos) coletados em 10 habitats com características distintas (rios, canais, lagoas isoladas e conectadas) para descrever padrões espaciais e temporais de alguns fatores limnológicos. Em geral, o grau de conectividade das lagoas com o rio ao qual estão conectadas foi importante para determinar as suas características limnológicas. Estas diferenças são esperadas porque os rios que chegam à planície de inundação vêm de diferentes regiões geológicas e estão sujeitos a diferentes impactos humanos. Em grandes escalas espaciais, tais diferenças contribuem para o aumento da diversidade de habitats da zona sujeita a inundações e assim, a sua alta biodiversidade. A respeito da variação temporal, observou-se um aumento nos valores de disco de Secchi e diminuição na carga de fósforo total no canal principal do rio Paraná nos últimos 20 anos. Embora estas mudanças estejam diretamente atribuídas ao efeito cascata de vários reservatórios a montante, o fechamento da represa de Porto Primavera em 1998 realçou este efeito. O aumento na trans...

Evaluation of a new sampling method for assessing Cladocera richness (Crustacea, Branchiopoda) in macrophyte-rich wetlands

“…Studies of wetlands have been conducted in Brazil on large floodplains, such as the Parana´River floodplain and the Pantanal (e.g., Roberto et al, 2009;Alho, 2011). These two large Brazilian wetlands have extremely rich Cladocera fauna, with estimates ranging between 60 and 85 species (Hollwedel et al, 2003;Serafim-Ju´nior et al, 2003;Junk et al, 2006).…”

Variability of δ13C and δ15N in three zooplankton species from the Upper Paraná River floodplain

“…1). These environments have distinct features that may influence the structure of the local communities (ROBERTO et al 2009).…”

Novel Diversity of Deeply Branching Holomycota and Unicellular Holozoans Revealed by Metabarcoding in Middle Paraná River, Argentina

“…The hydrochemistry characterization of the area has been previously reported (Depetris, 1976;Devercelli, 2006;Roberto et al, 2009). One of the main characteristics of this river is the fluctuation of the water volume (Roberto et al, 2009).…”

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