TROPHIC STATE AND CYANOBACTERIAL ABUNDANCE ALONG YEAR IN AN ARTIFICIAL PAMPEAN LAKE

FERNANDEZ, C.; PARODI, E.R; CACERES, E.J.

Santa Catarina

Workshop; GLEON 10; 2010

Universidade de Santa Catarina

The detriment in the trophic status and the development of cyanobacterial blooms are a major threat to the sustainability and safety of water resources around the world. Paso de las Piedras Reservoir is an artificial lake located in the southern part of Buenos Aires Province, Argentina. This lake is the unique water supply source for about 400000 inhabitants. The current trophic status was evaluated applying two different classification criteria on physicochemical and biological data over a period of a year (June 2004 to June 2005). The structure and abundance of the phytoplankton community was also studied. Cyanobacteria, green algae and diatoms were the most important constituents; cyanobacteria dominated from December 2004 until May 2005, during summer and early autumn, the product of a large relative abundance mainly of A. circinalis and M. natans. These high concentrations of cyanobacteria characterized a bloom with an average density of 133.05×103 cells.mL–1, and an average chlorophyll concentration of 28.7 mg.m–3. Four of the cyanobacterial species found are potentially producer of toxins. Considering the two trophic classification systems, and based on total phosphorus data, the reservoir is classified within the hypertrophic category. In contrast, considering only the chlorophyll and turbidity data, the lake would be classified within the eutrophic category.