Is similar the distribution of Chironomidae (Diptera) and Oligochaeta (Annelida, Clitellata) in a river and a lateral fluvial area?

Daniela Aparecida Silveira Cesar,Raoul Henry

doi:10.1590/s2179-975x1217

Daniela Aparecida Silveira Cesar, Raoul Henry

Open Access

https://doi.org/10.1590/s2179-975x1217

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Abstract

Abstract Numerous factors may affect the pattern of distribution of benthic fauna in a river mouth region and, among the macroinvertebrates, Chironomidae and Oligochaeta are the most abundant groups and most tolerant to environmental changes. Aim The aim of this study was to evaluate the controlling factors of and a possible similarity between Chironomidae and Oligochaeta assemblies at two close sites, the mouth of the Guareí River into the Paranapanema River (São Paulo, Brazil) and its lateral fluvial area. Methods Fauna samples were collected every three months during one year. Water physical and chemical variables and sediment variables were also determined in the same period. Results Both assemblies presented low density variability over time in the lateral area due to sediment characteristics and environmental factors. Taxa Caladomyia, Parachironomus, Pristina sp., Pristina osborni, Bothrioneurum and Opistocysta funiculus were recorded at this site. The Guareí River presented both greater temporal and spatial variations, attributed mainly to a reduction in the water level. Greater organism abundance, especially of Chironomus and Tubificinae, was observed in the river. Conclusions Dissimilarity in temporal and spatial distributions of Chironomidae and Oligochaeta was attributed to peculiar characteristics of the two study sites, a river channel and a lateral area. Reduction in the water level over the year was the main controlling factor of Chironomidae and Oligochaeta richness and density in the river. In the lateral area, the presence and abundance of certain taxa were determined by the nature of the sediment and water physical and chemical variables.

Highlights

Wetlands lateral to water courses are commonly observed in medium and large size basins
The connection between the Guareí River and the lateral area was interrupted in May, as the water level was below the threshold of 563.60 m of connection/disconnection of Paranapanema River with the lateral areas, according to Henry (2005)
The greatest depth was recorded on the Guareí River in October 2013, when a period of decrease in water level began (Figure 2B) and increase in transparency occurred (Figure 3B)

Summary

Introduction

Wetlands lateral to water courses are commonly observed in medium and large size basins. The connection between the river and the marginal lentic ecosystems is determined by variations in the hydrological level of the water course over the year. The hydrologic pulse is the main controlling factor of aquatic fauna composition, richness and abundance on floodplains (Junk et al, 1989; Martins & Henry, 2004). Variation in the connectivity between floodplain environments is determined by flood pulse amplitude and frequency, which result in differences in potamophase (flood) and limnophase (isolation of lateral aquatic ecosystems) during the year (Neiff, 1997; Dawidek & Ferencz, 2016). Pulse intensity determines variations in floodplain lake morphometric parameters dependent on the topography of the landscape where it is located (Ferencz & Dawidek, 2016). Montalto & Paggi (2006) reported that variations in the water level, degree of disconnection and gradual desiccation of an area marginal to the Paraná River did not limit the distribution and abundance of Chironomidae

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