Biotic or abiotic factors: which has greater influence in determining the structure of rotifers in semi-arid reservoirs?

Daniele Jovem Da Silva Azevêdo,Wilma Izabelly Ananias Gomes,Danianne Enéias Porto,José Etham De Lucena Barbosa,Joseline Molozzi

doi:10.1590/s2179-975x2914

Daniele Jovem Da Silva Azevêdo, Wilma Izabelly Ananias Gomes + Show 3 more

Open Access

https://doi.org/10.1590/s2179-975x2914

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Abstract

ObjectiveThe objective of this study is to evaluate whether the distribution of structural attributes of rotifers in reservoirs in the semiarid region is more strongly influenced by abiotic or biotic environmental factors (density of cyanobacteria).MethodSampling occurred in two reservoirs in the Paraíba Basin, northeastern Brazil (Poções and Camalaú) during April and June 2012. Eight sampling points were distributed at two stations in each reservoir: the region near the entrance of the main tributary and region of the dam and collections were made in the limnetic and littoral zone in every season. To assess the abiotic influence and density of cyanobacteria in the distribution of the structural attributes of rotifers, environmental variables bivariate correlation was conducted in series.ResultsIn Poções reservoir, the distribution of rotifer biomass was negatively related to the density of cyanobacteria; among the environmental variables, chlorophyll-a and total nitrogen were negatively related to all of the tested structural attributes, while the concentrations of total phosphorus were strongly related to the abundance of rotifers. In the Camalaú reservoir, the biomass was a structural attribute with a stronger correlation to the density of cyanobacteria; between the environmental variables and Egeria densa, nitrate was negatively related to all of the attributes tested, while transparency was moderately related to the abundance, biomass and richness as well as Chara sp. with abundance.ConclusionsAssemblages of rotifers are more clearly related to environmental conditions, especially those indicative of trophic conditions, despite the density of cyanobacteria having been a factor that was positively related to the structural characteristics of rotifers and thus indicative of such structural assemblies. This can be used for analysis of local environmental condition factors.

Highlights

Rivers and their watersheds are constantly under anthropogenic influence (Duffy et al, 2007), which has driven ecologists in the development of studies that assess the functioning of ecosystems subjected to different levels of impacts (Moreno et al, 2009; Tixier et al, 2011)
Understanding the anthropogenic factors that affect the distribution of species as well as the structural attributes of communities are key elements in understanding the cause-effect that leads to reduction of local biodiversity, especially in freshwater bodies, which should help to propose management measures regarding the threats at regional and local scales (Bunn & Arthington, 2002; Badsi et al, 2010)
The concentration of total phosphorus was different for both reservoirs; the highest values were observed in the Poções Reservoir in the limnetic zone in the period of the high water level (273.27μg L–1±2.66)

Summary

Introduction

Rivers and their watersheds are constantly under anthropogenic influence (Duffy et al, 2007), which has driven ecologists in the development of studies that assess the functioning of ecosystems subjected to different levels of impacts (Moreno et al, 2009; Tixier et al, 2011). Reservoirs form a network of different elements in the landscape that contribute to local biodiversity conservation, being considered important sites for refuges of species richness (Tundisi, 1999; Brainwood & Burgin, 2009; Chester & Robson, 2013). The multiple uses of these water bodies combined with anthropogenic impacts on watershed, as well as the lack of management plans, has favored the artificial eutrophication which has led to a loss of water quality and biodiversity (Revenga et al, 2005; Serediak et al, 2014)

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