Factors affecting assemblage attributes of freshwater Oligochaeta in Neotropical shallow floodplain lakes

Vanessa Ernandes De Amo,Roger Paulo Mormul,Gisele Daiane Pinha,Jéssica Ernandes Da Silva,Flávio Henrique Ragonha

doi:10.1590/s2179-975x8717

Vanessa Ernandes De Amo, Roger Paulo Mormul + Show 3 more

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https://doi.org/10.1590/s2179-975x8717

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Abstract

Abstract Aim: Identify the effects of sediment composition and water conditions on diversity, richness, evenness, density and composition of freshwater Oligochaeta in shallow floodplain lakes. Methods We sampled 13 shallow floodplain lakes quarterly during the year 2010 in the Upper Paraná River floodplain. In each lake, four sediment samples were taken from the shore and central regions, three of them were used for biological analysis, and one for granulometric analysis. Concomitantly, temperature, dissolved oxygen, pH, conductivity, alkalinity, turbidity and chlorophyll-a were also measured. Initially, the biological samples were analyzed by a stereoscopic microscope. Oligochaeta individuals were identified under optical microscope at the lowest possible taxonomic level. For data analysis, we quantified density, richness, evenness and diversity index of freshwater Oligochaeta. In order to show differences between the months and the analyzed lakes, in relation to the percentages of coarse and fine organic material, the nonparametric Kruskal Wallis test was used. We also calculated the sediment granulometric diversity using the Shannon-Wienner index, using a simple regression analysis. We correlated assemblage attributes of Oligochaeta with sediment diversity and the assemblage species with the limnological variables using the Spearman correlation. Results A total of 2,090 individuals were found distributed among 27 species. From the total individuals number, 57% were Pristina americana, followed by Dero (Dero) righii with 13%. Assemblage attributes were not significantly correlated with sediment diversity, and 7 of the 27 species recorded showed significant correlations with at least some of the abiotic variables. Conclusions We verified that the abiotic variables of the water present greater influence on the attributes of the assemblage of freshwater Oligochaeta, when compared with sediment influences. Although we found low local diversity of this group, the wide range of water conditions offered by lakes culminates with a great species richness considering the whole landscape.

Highlights

Floodplains are widely recognized by their high environmental heterogeneity (Thomaz et al, 2007; Lansac-Tôha et al, 2009), that comes from the mosaic of aquatic, terrestrial and transitional habitats (Thomaz et al, 2004)
We observed that in relation to the coarse organic matter the month of March differed from the months of June and September, whereas for the fine organic matter there were no differences between the months
We found no correlation between Oligochaeta community attributes and habitat heterogeneity, indicating that habitat structural components are not the main predictor of Oligochaeta assemblage in these shallow floodplain lakes

Summary

Introduction

Floodplains are widely recognized by their high environmental heterogeneity (Thomaz et al, 2007; Lansac-Tôha et al, 2009), that comes from the mosaic of aquatic, terrestrial and transitional habitats (Thomaz et al, 2004). Lakes are very common environments in floodplain areas, which are characterized by high accumulation of mud and organic matter (Knoppers, 1994; Bilia et al, 2015) The content of this and the granulometric composition of the sediment exert great influence on aquatic biodiversity (Súarez et al, 2001; Takeda & Fujita, 2004; Príncipe & Del Corigliano, 2006) for differences in both complexity and environmental heterogeneity among lakes (Pressinatte Junior et al, 2016). Benthic invertebrates compose a diverse and abundant community in the Upper Paraná River floodplain (Pinha et al, 2016) These organisms reflect sediment conditions (Bechara, 1996; Takeda & Fujita, 2004) and are strongly influenced by environmental conditions and show reduced mobility in the water (Würdig et al, 2007). Oligochaeta plays an important role representing one of the most abundant group (Takeda, 1999; Ezcurra de Drago et al, 2005; Takeda et al, 2017), which occur in almost all freshwater environments of Neotropical regions (Stevaux & Takeda, 2002; Behrend et al, 2009; Ragonha et al, 2013; Gonzáles, 2015; Flores & Aguirre, 2003)

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