Limnology of Dr. C. Gelsi's reservoir (El Cadillal), Tucumán, Argentina. IV

Spatio-temporal changes of phytoplankton

Abstract

The aim of this paper was to evaluate the spatial and seasonal changes of the phytoplankton in the limnetic area of Dr. Gelsi?s reservoir (El Cadillal), Province of Tucuman, Argentina. Algal richness, abundance, species diversity, biomass, and the statistical analysis of algal community at different levels of depth were the phytoplanktonic parameters studies for two periods, in which important temporal fluctuations of the phytoplankton related to environmental factors were registered. Phytoplankton density and biomass decreased markedly during the high water months due to the dilution effect. In general, algal richness and species diversity were lower at higher depths, the latter showing a direct correlation with water discharge closely related to the volume. Cluster analysis based on phytoplankton structure emphasized the importance of the common species present all along the profile during the studied years (Aulacoseira granulata (Ehrenberg) Simonsen, Cyclotella meneghiniana Kützing and Closterium acutum var. variabile (Lemmermann) Geitler) and those characteristic of surface and 10 meters, indicated differences between surface samples of the summer months for both periods, and it grouped the 10 m and bottom samples.