Influence of a waterfall over richness and similarity in adjoining pools of an Atlantic Rainforest stream

Abstract

Aim:The main goal of the study was to determine the effect of the Morato Fall in the richness and composition of the aquatic animal community; Methods: We compared faunal richness and similarity in four substrate samples from two pools separated by a waterfall in the Morato River, southern Brazil; Results: The richness was not significantly different, although the upstream pool had 72 taxa and the downstream one just 65. On the other hand, composition was poorly similar, just a 36.5% similarity between the two sites; Conclusions: That indicates a strong influence of the waterfall, mainly on organisms which spent its entire life cycle on the water, such as fish and small crustaceans. That allow aquatic insects, a group with airborne adult phase and, therefore, able to disperse up to the upstream pool, to evolve with less predatory pressure, becoming the top group in the food web of this environment.Resumo: Objetivo: O objetivo principal foi determinar o efeito do Salto Morato na riqueza e na composição da comunidade aquática; Métodos: Nós comparamos a riqueza e a similaridade da fauna em amostras de quatro substratos de dois poços separados por uma cachoeira no Rio Morato, no sul do Brasil; Resultados: A riqueza não foi significativamente diferente, embora o poço acima do salto tenha apresentado 72 taxa e o poço abaixo do salto apenas 65. Por outro lado, a fauna apresentou-se pouco similar, com apenas 36,5% de similaridade entre os poços; Conclusões: Isso indicou uma forte influencia da presença da cachoeira, principalmente nos organismos que tem todo o ciclo de vida na água, como os peixes e pequenos crustáceos. Isso permite que os insetos aquáticos, que tem fase adulta alada e, portanto, a capacidade de se dispersar até o poço acima do salto, se desenvolvam sem a pressão de seus principais predadores e tornem-se, naquele ambiente, os organismos de topo da teia trófica.

Stream Fish in the Aripuanã River Upstream and Downstream of the Dardanelos-Andorinhas Waterfall Complex, State of Mato Grosso, Brazil

“…(Mendonça et al 2005, Espírito-Santo et al 2009, Dias et al 2010, Fernandes et al 2013, values similar to those reported here. Waterfalls are important barriers for aquatic organisms, preventing the movement and the exchange of species among regions (Rahel 2007, Jönck & Aranha 2010, Torrente-Vilara et al 2011. This study found a marked effect on the Dardanelos-Andorinhas waterfalls complex, which acted as natural barrier to fish species.…”

“…The waterfalls act as natural ecological barriers limiting fish dispersal processes which causes significant differences in species composition between rivers stretches located upstream and downstream of the waterfall (Jönck & Aranha 2010, Torrente-Vilara et al 2011. Besides that, waterfall may affect genetic structure and increase genetic distance between local populations (Kano et al 2012).…”

Longitudinal distribution of the ichthyofauna in a tributary of Tietê River with sources on the Basaltic Cuestas of São Paulo, Southeastern Brazil

“…& Garavello (2007), studying the Pâ ntano River and showing large varieties of species among the sites separated by Pântano waterfall, where only 13 species out of 63 were recorded. Also, Jonck & Aranha (2010) have studied the aquatic population of two pools, separated by a waterfall in a Atlantic Rainforest stream and have concluded that there is a strong influence of the obstacle, the waterfall, especially to the organisms that spend all their life cycle in water.…”