Thomaz Aurélio Pagioro

Decomposition of Eichhornia azurea from limnologically different environments of the Upper Paraná River floodplain

Morphometrically distinct populations of Eichhornia azurea (Swartz) Kunth from environments with different limnological characteristics (Cortado Canal and Guaraná Lake, both in the Upper Paraná River floodplain), were incubated in the laboratory for 90 days. During this period, they were allowed to decompose in water of their original environment, or in water from reciprocally exchanged environments. The objectives were (a) to determine decomposition rates and changes in concentration of carbon, nitrogen and phosphorus in plant tissue and (b) to verify whether these rates and changes in tissue were affected by plant origin or by the characteristics of the water in which they were decomposing. Three distinct phases of decomposition were observed. In the first phase, ash content was rapidly lost. In the second, nitrogen increased and phosphorus decreased. In the third, both nitrogen and phosphorus increased. The results suggest that (a) changes in ash content and phosphorus concentration were similar in both environments; (b) the concentration of nitrogen remaining in the plant tissue was affected differently (ANOVA-Repeated, p<0.05) by the water from Cortado Canal and Guaraná Lake; and (c) plants from different environments lost weight at different rates.

Bacterioplankton features and its relations with doc characteristics and other limnological variables in Paraná river floodplain environments (PR/MS-Brazil).

Since the introduction of the Microbial Loop concept, many studies aimed to explain the role of bacterioplankton and dissolved organic carbon (DOC) in aquatic ecosystems. Paraná River floodplain system is a very complex environment where these subjects were little explored. The aim of this work was to characterize bacterial community in terms of density, biomass and biovolume in some water bodies of this floodplain and to verify its temporal variation and its relation with some limnological variables, including some indicators of DOC quality, obtained through Ultraviolet-visible (UV-VIS) and fluorescence spectroscopic analysis. Bacterial density, biomass and biovolume are similar to those from other freshwater environments and both density and biomass were higher in the period with less rain. The limnological and spectroscopic features that showed any relation with bacterioplankton were the concentrations of N-NH4 and P-PO4, water transparency, and some indicators of DOC quality and origin. The analysis of these relations showed a possible competition between bacterioplankton and phytoplankton for inorganic nutrients and that the DOC used by bacterioplankton is labile and probably from aquatic macrophytes.

Spatial and seasonal distribution of chromophoric dissolved organic matter in the Upper Paraná River floodplain environments ( Brazil)

AIM: Our aim was to identify dissolved organic matter (DOM) main sources in environments of the Upper Parana River floodplain and their seasonal and spatial variation. METHODS: Ultraviolet-visible and fluorescence spectroscopy were utilized. The samples were obtained from November 2007 to September 2008 in six lakes of the floodplain. RESULTS: DOM quality differs among environments and also between rainy and dry season. The environments connected with Parana River showed a high variation on the allochthonous/autochthonous proportion. Aquatic macrophytes might represent an important contribution to DOM in Garcas and Osmar lakes. CONCLUSIONS: In general, environments connected to Parana River have a greater influence of autochthonous DOC, while the others are most influenced by allochthonous inputs.

Eichhornia azurea decomposition and the bacterial dynamic: an experimental research.

Organic decomposition is a complex interaction between chemical, physical and biological processes, where the variety of aquatic vascular plants is essential for the trophic dynamics of freshwater ecosystems. The goal of this study was to determine the aquatic macrophyte Eichhornia azurea (Sw.) Kunth decomposition rate, the time relation with the limnological parameters, and whether this relationship is a result of decomposition processes. To that end, we collected water and leaves of E. azurea in Surf Leopoldo, PR. The experiment consisted of two treatments: 25 containers with 450 mL of water and 0.8 g of biomass dry weight were used with or without the addition of macrophytes. Samples were collected in triplicate at times 0, 3 h, 6 h, 12 h, 24 h, 72 h, 120 h, 168 h and 240 h. When the container was removed, the plant material was dried in an oven. After 48 h, the material was measured to obtain the final dry weight. Analyses of pH, conductivity, dissolved oxygen, total phosphorus N-ammonia (NH4), soluble reactive phosphorus (PO4) and dissolved organic carbon were performed, and the decomposition rate was calculated. The results showed significant temporal variation of limnological parameters in the study. Additionally, dissolved oxygen, conductivity, dissolved organic carbon and total phosphorus were correlated with the dry weight of the biomass, suggesting that E. azurea decomposition significantly interferes with the dynamics of these variables.

Diel Variation Related to Thermal Mixing in a Subtropical and in a North-Temperate Shallow Floodplain Lake

ABSTRACT Shallow floodplain habitats connected to large rivers undergo seasonal flooding making them integral parts of large river ecosystems. In tropical and subtropical regions, water mixing in these habitats is described as polymictic, yet little description exists for other large river floodplain lakes. In this study, the effect of thermal input on die1 mixing was compared between subtropical Garças Lake (GL)(1.2 m depth) connected to the Paraná River, Brazil and temperate Crane Lake (CL)(0.5 m depth) connected to the Illinois River, USA. Physical, chemical, and microbial variables were measured at 3 h intervals on clear, nearly windless (avg. < 1.2 m s−1) days in summer (GL, 8–9 Jan 02; CL, 8–9 Aug 02). Nocturnal, convective mixing was evident for temperature (range: GL, 28–33 °C; CL, 23–32 °C) and oxygen (range GL: 23–196%; CL: 24–200%) in each system by nightfall (1930h) and correlated with differences in nitrate and ammonia. Although total bacterial density differed between surface and bottom water samples by afternoon, it was similar at both depths by evening (CL, 2230h) or early morning (GL, 430h)Diel mixing occurred in both systems and has important implications in nutrient cycling, coupling of oxic-anoxic processes, and distribution of microbiota.

STUDY OF THE STRATIFICATION PROCESS AT THE RESERVOIR OF THE HYDROELECTRIC POWER PLANT GOV. PEDRO VIRIATO PARIGOT DE SOUZA (CAPIVARI-CACHOEIRA), PARANÁ, BRAZIL.

The study of the stratification processes in reservoirs is important because they happen along with several physical and chemical changes in the water, as in the distribution of dissolved gases and nutrients. The aim of this work was to study the stratification process of the Capivari-Waterfall Hydroelectric Power Plant, based on the data of the vertical profiles of dissolved oxygen and temperature, as well as the comparison of them with the calculation of Froudes Densimetric Number, and reservoir residence time. The data used are part of the self-monitoring program carried out by COPEL. These data were collected quarterly between 2005 and 2016. The hydraulic and operational data from the reservoir were used to calculations. According to the measurements of dissolved oxygen and temperature, it was considered to be stratified during almost all the year, with a trend of circulation in the colder months, this behavior characterizes lakes with warm monomictic circulation pattern. Therefore, the result of Froudes Densimetric Number, corresponded correctly with the observed. Regarding the residence time, this was not consistent with the results obtained, from the models. The use of different methodologies in evaluating circulation in reservoirs should be used in order to make the best management decision.

Large scale distribution of bacterial communities in the upper Paraná River floodplain

A bacterial community has a central role in nutrient cycle in aquatic habitats. Therefore, it is important to analyze how this community is distributed throughout different locations. Thirty-six different sites in the upper Paraná River floodplain were surveyed to determine the influence of environmental variable in bacterial community composition. The sites are classified as rivers, channels, and floodplain lakes connected or unconnected to the main river channel. The bacterial community structure was analyzed by fluorescent in situ hybridization (FISH) technique, based on frequency of the main domains Bacteria and Archaea, and subdivisions of the phylum Proteobacteria (Alpha-proteobacteria, Beta-proteobacteria, Gamma-proteobacteria) and the Cytophaga-Flavobacterium cluster. It has been demonstrated that the bacterial community differed in density and frequency of the studied groups. And these differences responded to distinct characteristics of the three main rivers of the floodplain as well as to the classification of the environments found in this floodplain. We conclude that dissimilarities in the bacterial community structure are related to environmental heterogeneity, and the limnological variables that most predicted bacterial communities in the upper Paraná River floodplain was total and ammoniacal nitrogen, orthophosphate and chlorophyll-a.