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

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.Keywords: temporal and spatial variation, Chironomidae, floodplain, damming. Conseqüências da construção de um reservatório a montante da planície aluvial do Alto Rio Paraná (Brasil): análises temporais da comunidade Chironomidae em um período de oito anos ResumoEste trabalho teve por objetivos identificar padrões de variação temporal e alterações ocorridas na estrutura da comunidade de larvas de Chironomidae de dois rios da planície aluvial do Alto Rio Paraná nos anos subseqüentes ao fechamento de um reservatório à montante, Porto Primavera. As amostras foram coletadas de 2000 a 2007 com um pegador do tipo Petersen, modificado. As larvas de Chironomidae foram identificadas até a menor categoria possível. A elevada riqueza de Chironomidae observada nos rios Paraná e Ivinhema (100 morfoespécies), quando comparada com a média mundial para rios de mesmo porte (44 espécies), ressalta a importância desses ambientes para a manutenção da biodiversidade. Tanto pela dominância, como também pela composição e densidade numérica, verificou-se que os anos de 2000 e 2001 diferiram dos demais. Este foi um período de fortes alterações no fluxo do Rio Paraná causado pela instalação do reservatório Porto Primavera aliado a uma grande seca ocorrida no final de 2001. Uma nova composição de morfoespécies e maior semelhança entre os anos seguintes são um indicativo da recuperação e adaptação da comunidade. Apesar das mudanças na composição de morfoespécies a diversidade foi mantida e a comunidade continua respondendo às flutuações do nível hidrométrico. Palavras-chave:variações espaciais e temporais, Chironomidae, planície de inundação, represamento. Rosin, GC. et al. 592

Studies in South-Occidental Amazon: contribution to the knowledge of Brazilian Chironomidae (Insecta: Diptera)

“…In our study in the Acre river, we recorded Chironominae, Tanypodinae and Orthocladiinae subfamilies that are the most commonly recorded in aquatic habitats in Brazil. Chironominae were the most specious subfamily, which confirms the observations of Fittkau (1971), Spies and Reiss (1996), Roque et al (2000) and Rosin and Takeda (2007) and Rosin et al (2009). We found 14 genera in the Acre river; however, it is difficult to compare these numbers with other studies in the Amazon, because most previous research on Chironomidae has been conducted in lentic environments or impacted habitats (CALLISTO, 1997;CALLISTO;ESTEVES, 1996;REISS, 1977a and b), or refer to Chironomidae in family taxonomic level (COUCEIRO et al, 2010;FIDELIS et al, 2008).…”

Using oligochaeta assemblages as an indicator of environmental changes

“…The rapid numerical increase of dams has caused widespread loss of freshwater habitats, especially waterfalls, riparian floodplains and wetlands. Therefore, the construction of dams can cause profound negative effects on aquatic biodiversity because the natural seasonal patterns to which the fauna has adaptations is altered, and normal seasonal migration paths (drifts) are blocked (Rosenberg et al 2000). Callisto et al (2005) observed that reservoirs in cascades cause significant changes in the original continuum of a river, altering the thermal heterogeneity, the connectivity, the fine and the coarse particulate organic matter rates.…”

“…The flow regulation and stratification patterns developed in reservoirs frequently impact the biota downstream in four ways (Cortes et al 2002): i) alteration of physical and chemical characteristics associated with the release of water and sediment derived from the hypolimnion, that affect life history and density of macroinvertebrates (Cortes et al 2002); ii) alteration of available food resources to aquatic biota, specially through changes in the particulate organic matter (McAllister et al 2001); iii) creation of unstable environment due to daily changes in water level, increasing invertebrate drift (Hansen and Closs 2007); and iv) reduction of water released downstream, which modify abundance and diversity of benthic fauna (Bunn and Arthington, 2002). These effects have been demonstrated in several regulated rivers, where alterations in discharge have caused changes in the structure of the aquatic community (Pardo et al, 1998;Rosin et al, 2009).…”

Chironomidae feeding habits in different habitats from a Neotropical floodplain: exploring patterns in aquatic food webs

“…According to Rosin et al (2009), during the historical formation of their life cycles, aquatic species developed strategies that depend on the natural flow regime. Consequently, likewise that many other aquatic communities from floodplains, both the distribution of Chironomidae, as the adaptation strategies and feeding habits of the larvae are drive by hydrological dynamics.…”