Factors structuring the spatial distribution of Chironomidae larvae community in the floodplain of the northern Pantanal, Brazil

Maitê Tambelini Dos Santos,Ibraim Fantin-Cruz,Pierre Girard,Claudia Tasso Callil

doi:10.1590/s2179-975x2013000200004

Abstract

AIM: In order to identify the factors structuring the spatial distribution of the Chironomidae community, we analyzed the effects of water and sediment characteristics, flood duration and type of phytophysiognomic unit on the taxa composition of this community. MÉTODOS: O estudo foi realizado em 26 parcelas do Sítio de Amostragem de Longa Duração (SALD), localizado em uma área sazonalmente inundável na parte norte do Pantanal (Brasil). The study was conducted at 26 plots of the Long-Term Sampling Site, located in a seasonally flooded area in northern Pantanal (Brazil). Sediment samples were taken from each plot to analyze the Chironomidae community, organic matter and particle size; limnological parameters (depth, water temperature, dissolved oxygen, electrical conductivity and pH); besides the duration of flood. RESULTS: We identified 432 individuals distributed into 21 Chironomidae taxa. Polypedilum and Ablabesmyia were the most frequent spatially. The multivariate multiple regression analysis showed that the community composition was significantly related to the flood duration and grain size characteristics, but not to phytophysiognomic units and limnological parameters. Plots with predominantly sandy substrate and flooded for a shorter time presented a greater occurrence of taxa. CONCLUSIONS: The gradient produced by the spatial distribution of sediment grain size and flood duration determined the distribution of Chironomidae taxa. Changes in the hydrological functioning of the Pantanal, such as those from reservoir construction in the uplands region and roads and dykes construction in the floodplain could then impact the local chironomid biodiversity.

Highlights

The seasonal hydrological variation is an important component for the maintenance of the ecological functioning of floodplain ecosystems and controls the structure of biological communities (Junk et al, 1989; Tockner et al, 1999; Junk et al, 2006).In floodplains, larvae of the family Chironomidae can be the most abundant invertebrate group (Sommer et al, 2004; Benigno and Sommer, 2008)
Given the need to understand what factors influence the spatial distribution of Chironomidae community in the seasonally flooded area of the northern Pantanal, the objective of this research was to characterize the Chironomidae taxa in terms of occurrence, and to respond the following questions: the relative frequency of taxa vary spatially with: (i) the characteristics of the water, sediment and flood duration? (ii) with the different types of phytophysiognomic units?
We reduce the dimensionality of the data of the Chironomidae larvae composition using a non-metric multidimensional scaling (NMDS), with the software PC-ORD 5.0

Summary

Introduction

The seasonal hydrological variation is an important component for the maintenance of the ecological functioning of floodplain ecosystems and controls the structure of biological communities (Junk et al, 1989; Tockner et al, 1999; Junk et al, 2006).In floodplains, larvae of the family Chironomidae can be the most abundant invertebrate group (Sommer et al, 2004; Benigno and Sommer, 2008). The Chironomidae community usually changes in response to physical and chemical variations of the water (Higuti and Takeda 2002). Studies on the Chironomidae community structure in the Pantanal are restricted to permanent water bodies (Ezcurra de Drago et al, 2004; Marchese et al, 2005; Aburaya and Callil, 2007). All these studies described the relationship between this community and environmental variables, such as the type of sediment and physicochemical parameters of the water; the effect of the flood duration in the floodplain had not been investigated

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