Phytoplankton of subtropical reservoirs of northwestern Argentina

Cabra Corral and El Tunal reservoirs of High Juramento Basin, are the most important reservoirs in the province of Salta (Argentina). The composition and structure of algal assemblages in seasonal sampling in both dams during February, May and October of 1998-2011 according standard techniques were analyzed. The inventory of species includes a total of 334 spp., being the most diverse groups: Chlorophyta (116), Bacillariophyta (112) and Cyanobacteria (64). The phytoplankton abundance and species diversity were associated with changes in water discharges. The highest values of richness and diversities, were reached during the rainy season the situation being reversed in low water when it tends to increase the total biomass, except during Dinophyta blooms. The emergence of potentially toxic cyanobacteria was more significant in the late summer and autumn. Although the total number of species recorded is high compared to other subtropical reservoirs, only a few can be considered common or frequent (Aulacoseira granulata, Cyclotella meneghiniana, Sphaerocystis schroeteri Chroomonas minuta). Biomass was associated locally with rainfall and / or management of hydrometric level and regional level with the surface area of the reservoirs.