Consequences of dam construction upstream of the Upper Paraná River floodplain (Brazil): a temporal analysis of the Chironomidae community over an eight-year period

Gc Rosin,Dp Oliveira-Mangarotti,Cmm Butakka,Am Takeda

doi:10.1590/s1519-69842009000300014

Gc Rosin, Dp Oliveira-Mangarotti + Show 2 more

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https://doi.org/10.1590/s1519-69842009000300014

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Abstract

Our study aimed to identify patterns of temporal variation and changes in the structure of the community of Chironomidae larvae in two rivers in the Upper Paraná River floodplain after the construction of a reservoir upstream (Porto Primavera). Samples were taken with a Petersen grab, and were obtained between 2000 and 2007. Chironomidae larvae were identified down to the lowest taxonomic level possible. The high richness of Chironomidae observed in the Paraná and Ivinhema Rivers (100 morphospecies) in comparison to the world average of rivers of the same size (44 species) emphasizes the importance of these habitats for the maintenance of biodiversity. The composition and density of Chironomidae in the years 2000 and 2001 differed from the other years. This period was characterized by extreme changes in the Paraná River flow caused by the closing of the Porto Primavera Dam, which added to a severe dry period in late 2001. The different compositions of morphospecies and the higher similarities in subsequent years are indicative of the recovery and adaptation of the community. In spite of the changes in the composition of morphospecies, diversity was maintained and the community continued to respond to fluctuations in the hydrometric level.

Highlights

Research has demonstrated that the Upper Paraná River floodplain has been severely affected by anthropogenic effects such as the removal of riparian vegetation, biocide loads, discharge of domestic sewage and, most importantly, the construction of dams (Agostinho et al, 2008)
The combined action of hydrological events in the Paraná and Ivinhema Rivers is primarily responsible for the geomorphological and ecological processes occurring across the floodplain (Rocha 2002)
The clustering observed between 2004 and 2007 in axis 1 of the Principal Component Analysis (PCA) was influenced by the decrease in the percentages of medium and fine sand in the Paraná River, which is probably due to the geomorphological changes caused by the closing of the Porto Primavera Dam (Souza-Filho et al, 2004)

Summary

Introduction

Research has demonstrated that the Upper Paraná River floodplain has been severely affected by anthropogenic effects such as the removal of riparian vegetation, biocide loads, discharge of domestic sewage and, most importantly, the construction of dams (Agostinho et al, 2008). Dams have altered the natural flood regime, and the structure and dynamics of the floodplain (Agostinho et al, 2004). The first filling stage of the reservoir began in December 1998, and the second stage occurred only in March 2001. These filling activities changed the hydrological regime of the Upper Paraná River floodplain. Despite the sequence of reservoirs upstream, flood pulses are still the main factor controlling the structure and function of this ecosystem (Agostinho et al, 2008)

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