&lt;b&gt;Relationship between bacterial density and abiotic factors at different sediment depths of lakes in the Upper Paraná River floodplain

Natalia Fernanda Santana,Thomaz Aurelio Pagioro,Maria Do Carmo Roberto

doi:10.4025/actascibiolsci.v37i1.22240

Abstract

River-floodplain systems are known for their heterogeneity of habitats and the hydrological pulse, the main driving force, which increases nutrient concentrations at the onset of the flood due to leaching from the littoral region and decomposition. This decaying organic matter tends to be deposited in the sediment, where occur biogeochemical processes associated with microorganisms. This study aimed to characterize the vertical distribution of bacterial density in the sediment strata of six environments of the Upper Parana River floodplain, checking similarity as for bacterial density and physical and chemical conditions. To this end, we analyzed the following factors: total phosphorus, total Kjeldahl nitrogen, levels of organic and inorganic material, oxidation potential and particle size. The results evidenced a gradient of vertical distribution of bacterial density, with predominance of cocci, which possibly indicates no nutrient limitation in this limnic compartment. The analysis of variance was applied to determine significant differences between the layers of the sediment and environments. It can be observed a tendency of deposition of total-P and MI within the upper layers of all environments. More reducing potentials in the initial layers indicate a higher bacterial activity, since this region possesses a greater availability of most easily decomposable material.

Highlights

In river-floodplain systems, the hydrological pulse, the main driving force, provides heterogeneous aquatic habitats, creating favorable conditions for the maintenance of high biodiversity (JUNK et al, 1989; NEIFF, 1990)
This decaying organic matter tends to be deposited in the sediment, which comes to be the appropriate site to biogeochemical processes associated with microorganisms (D’HONDT et al, 2004; NELSON et al, 2007), and is crucial to the functioning of aquatic ecosystems (McDONALD et al, 2004)
The goal of this study was to characterize the vertical distribution of bacterial density in the sediment layers of lakes of the Upper Paraná River floodplain in relation to physical and chemical condition of the sediment, checking the similarity between the environments

Summary

Introduction

In river-floodplain systems, the hydrological pulse, the main driving force, provides heterogeneous aquatic habitats, creating favorable conditions for the maintenance of high biodiversity (JUNK et al, 1989; NEIFF, 1990). Biological Science different habitats of the floodplain, favoring the exchange of biological, physical and chemical material, enhancing the similarity between habitats (THOMAZ et al, 2007) In these systems, the concentrations of nutrients, especially nitrogen and phosphorus, increase early in the flood due to leaching from the littoral region and the decay of aquatic macrophytes The high deposition of organic matter in the littoral region of aquatic environments favors a rapid aerobic degradation in water-sediment interface, affecting the biogeochemical cycling of carbon and nutrients (HEDGES et al, 1999), and the process of decomposition and mineralization of this material is carried out by bacteria and supplies nutrients to primary producers (AZAM et al, 1983). The bacteria consume a significant part of the total photosynthetic production (BRUM; ESTEVES, 2001)

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