Using oligochaeta assemblages as an indicator of environmental changes

Abstract

We designed a field survey (the entire river length; not dammed: First and Second plateaus; dammed: Third Plateau) to test the hypothesis that the cascade of reservoirs promoted a reduction in species richness and changed the composition of Oligochaeta assemblage along the Iguaçu River. Changes in environmental variables and in richness and composition of Oligochaeta were summarized by Canonic Correspondence Analysis. Along the Iguaçu River, conductivity, and altitude decreased, whereas temperature increased. Oligochaeta composition showed a significant spatial variation, with higher abundances of the family Tubificidae and the genus Dero (Naididae) occurring in the First Plateau. In the Second and Third plateaus, few species were dominant, with increases in the presence of species of Naididae below dams. We found a clear decrease in species richness along the Iguaçu River. Moreover, we found that Oligochaeta assemblage was influenced by some environmental variables such as altitude, conductivity, substrate type and temperature, and by anthropogenic activities (human occupation and damming). The results supported the use of Oligochaeta as surrogate taxa to predict environmental changes along impacted (dammed and eutrophic) rivers. The validity of this was indicated by the strong and significant gradient registered, from the headwater to mouth of the Iguaçu River.Keywords: surrogate taxa, reservoir cascade, geomorphologic gradient, human occupation, Iguaçu River. Usando assembléias de Oligochaeta como um indicador de mudanças ambientais ResumoFoi delineada uma pesquisa de campo (toda extensão do rio; não barrado: Primeiro e Segundo planaltos; barrado: Terceiro planalto) para testar a hipótese de que a cascata de reservatórios promove redução na riqueza de espécies e muda a composição da assembléia de Oligochaeta ao longo do Rio Iguaçu. Mudanças nas variáveis ambientais e na riqueza e composição de Oligochaeta foram sumarizadas por Análise de Correspondência Canônica. Ao longo do Rio Iguaçu, a condutividade e a altitude diminuíram, enquanto a temperatura aumentou. A composição de Oligochaeta mostrou variação espacial significativa, com maiores abundâncias da família Tubificidae e do gênero Dero (Naididae) ocorrendo no Primeiro planalto. No Segundo e Terceiro planaltos, poucas espécies foram dominantes, com aumento na presença de espécies de Naididae abaixo de barragens. Foi encontrada uma clara diminuição na riqueza de espécies ao longo do Rio Iguaçu. Além disso, observou-se que a assembléia de Oligochaeta foi influenciada por algumas variáveis ambientais, como altitude, condutividade, tipo de substrato e temperatura, e por atividades antropogênicas (ocupação humana e barramento). Os resultados deste estudo suportam o uso de Oligochaeta como táxon substituto para predizer mudanças ambientais ao longo de rios impactados (barrados e eutróficos). A validade desse estudo foi indicada pelo forte e significativo gradiente, registrado da cabeceira à foz do Rio Iguaçu.Palavras-chave: taxon substituto, cascata de r...

Distribution of benthic macroinvertebrates in a tropical reservoir cascade

“…Because dispersal is limited in these species, they are directly dependent on the characteristics of the local environment (Callisto et al, 2005;Costa & Callisto, 2006;Behrend et al, 2012). As a result, neighboring locations may exhibit substantial differences in species richness and diversity (Poff, 1997).…”

“…The impact of river regulation on macroinvertebrates has been the focus of many studies worldwide (Behrend et al, 2012;Gillespie et al, 2014). Macroinvertebrates play essential role in aquatic systems, especially due to recycling and, in reservoirs, as important link in every food chain.…”

Macrozoobenthos structure in a temperate acid oligotrophic lake

“…Thus, the pH of water significantly influences the functioning of the water body by shaping its physico-chemical properties (Lampert & Sommer, 1996). In turn, it results in changes of biocoenosis of the reservoir, because the living organisms are directly dependent on the characteristics of the local environment and they clearly reflect the ecological conditions of the aquatic ecosystems they inhabit (Callisto et al, 2005;Behrend et al, 2012).…”

Effect of substrate change on macrozoobenthos structure

“…Moreover, they can clearly reflect the ecological conditions of the aquatic ecosystems they inhabit (Callisto et al, 2005;Behrend et al, 2012). Due to their weak moving ability, the bottom fauna is a very good indicator reflecting also changes in an aquatic ecosystem (Moreno & Callisto, 2006).…”