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Preliminary data on the phytoplankton and the physico chemical characteristics of the reconquista river buenos aires argentina an urban polluted river

, : Preliminary data on the phytoplankton and the physico chemical characteristics of the reconquista river buenos aires argentina an urban polluted river. Revue d'Hydrobiologie Tropicale 23(4): 283-296

The evolution of several biotic and abiotic parameters during the period November 85-February 87 along the urban highly polluted Reconquista River was investigated. Sampling was done monthly in four stations. Correlations between the density of the surface phytoplankton communities and several physical and chemical properties of water (temperature, pH, conductivity, dissolved oxygen and dissolved solids) were made; the most relevant factor was the dissolved oxygen (OD). During the studied period important fluctuations of both biotic and abiotic measured parameters were recorded. The main features were the decrease of OD down to the values close to zero and the considerably high concentrations of Zn (1000-4000 .mu.g.cntdot.l-1) in the water of the stations located downstream. The pH varied between 6.4 and 10.0; the water temperature followed the pattern of the regular climatic cycle without important spatial modifications; while the conductivity followed a profile similar to that of dissolved solids. The mean chlorophyll a concentrations were relatively low (4 .mu.g.cntdot.l-1); much higher values (35 .mu.g.cntdot.l-1) were found only when water blooms occurred. The analysis of phytoplankton showed the presence of 160 taxa. The biomass of the Bacillariophyceae was always dominant followed by the Chlorophyceae. In the more polluted points there was observed important increase of the Cyanophyceae and the Euglenophyceae.


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