The role of limnological variables and habitat complexity in impacted tropical streams as regulatory factors on the flagellate protozoa community

Janielly Carvalho Camargo,Ludgero Cardoso Galli Vieira,Luiz Felipe Machado Velho

doi:10.1590/s2179-975x2012005000038

Janielly Carvalho Camargo, Ludgero Cardoso Galli Vieira + Show 1 more

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https://doi.org/10.1590/s2179-975x2012005000038

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Abstract

OBJECTIVE: To contribute to the knowledge of patterns of spatial and seasonal distribution of composition and species richness of flagellate protozoa in tropical impacted streams and to identify which variables (physical and chemical or descriptor variables of habitat complexity) control these attributes in these environments. METHODS: Samplings were performed in 10 tropical streams (5 urban and 5 rural) in two periods (summer and winter). Limnological variables were determined on the field (except for the concentration of nutrients), the habitat macrostructure was visually estimated in situ, using a quadrat and the species identification was performed in vivo, under optical microscope. RESULTS: In total, 106 taxa were identified, the order Euglenida was that contributed most to the species richness, probably due to the high tolerance to environmental changes. Multivariate analyses (ANOSIM and MDS) evidenced significant spatial and seasonal differences both for composition and species richness. The Bioenv and Mantel Test indicated that the patterns of composition and richness were controlled by physical and chemical variables indicative of water quality (pH, electrical conductivity, and concentration of nutrients). However, the species richness was also influenced by the habitat structural complexity and by its stability, which can be disturbed by the rainfall regime. CONCLUSIONS: The results showed that flagellate protozoa are sensitive to environmental changes, and thus can be used as efficient bioindicators of water quality, as has already been done with other aquatic organisms. Moreover, human activities that cause changes in the channel morphology of lotic ecosystems may determine the occurrence of flagellate species, once the simplification of the habitat structure leads to the reduction of species in the environment.

Highlights

Flagellate protozoa are found in almost every aquatic biotope, where play important role on the metabolism of these ecosystems, especially given their great ability of energy and matter transfer along aquatic food chains (Azam et al, 1983; Arndt et al, 2000), since when consumed by ciliate or zooplankton (Arndt, 1993; Weisse, 1990), they transfer to these organisms the energy obtained in the consumption of bacteria, virus, picophytoplankton, nanophytoplankton and dissolved organic carbon (Xu et al, 2005), reintroducing into the aquatic food webs the matter and energy that would be eliminated (Azam et al, 1983)
To detect a possible environmental gradient, the biotic variables were summarized by a principal component analysis and the three first axes retained for interpretation explained 55% of the total data variability (Figure 2; Table 2)
Flagellate protozoa play an important role in the carbon cycle in aquatic ecosystems, ecological researches with these organisms usually do not have any taxonomic detail (Arndt et al, 2000)

Summary

Introduction

Flagellate protozoa are found in almost every aquatic biotope, where play important role on the metabolism of these ecosystems, especially given their great ability of energy and matter transfer along aquatic food chains (Azam et al, 1983; Arndt et al, 2000), since when consumed by ciliate or zooplankton (Arndt, 1993; Weisse, 1990), they transfer to these organisms the energy obtained in the consumption of bacteria, virus, picophytoplankton, nanophytoplankton and dissolved organic carbon (Xu et al, 2005), reintroducing into the aquatic food webs the matter and energy that would be eliminated (Azam et al, 1983). The pigmented flagellates may expressively contribute with the primary production in aquatic ecosystems (Safi and Hall, 1997) This community can be controlled by both biotic and abiotic factors, such as food resource availability, predation pressure, pH, electrical conductivity, dissolved oxygen, trophic state, and climatic seasonality (Pace and Funke, 1991; Arndt, 1993; Samuelsson et al, 2006; Araújo and Godinho, 2008; Camargo and Velho, 2011). The water quality can influence the distribution of these organisms, as reported by some authors (Jiang and Shen, 2005; Araújo and Godinho, 2008) In this way, it is essential to determine the major factors controlling the structure and dynamics of this community in these environments, in order to subsidize the elaboration of proposals for monitoring, management, conservation and restoration of these ecosystems, which have been extensively modified in the recent decades by the various uses and occupations of the land

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