PHYTOPLANKTON AND WATER QUALITY IN A SHALLOW LAKE: A RESPONSE TO SECONDARY SALINIZATION (ARGENTINA).

This study analyzes the phytoplankton structure and dynamics, as well as the main limnological characteristics in Los Coipos Lake, located in the Reserva Ecológica Costanera Sur (Buenos Aires, Argentina). Phytoplankton generic composition was studied before (April-June 1998), during (July 1998-December 1999), and after (January-October 2003) pumping from the Puelche aquifer waters, characterized by extremely high conductivity values. The capacity of natural recovery from salt contamination was analyzed. The 1998-1999 parameters were obtained from a technical database (Aguas Argentinas water supply company), while two-monthly samples were collected and analyzed between January and October 2003. Decrease and replacement of genera was related to the conductivity increase; recovery of the number of genera was recorded once the input ceased. Chlorophyceae and Cyanophyceae were responsible for the greatest phyto-plankton densities. During ground-water input, four high phytoplankton density events were recorded. One hundred fifty-three infrageneric phytoplanktonic and tichoplanktonic taxa were registered during 2003, together with high total phytoplankton densities. Phytoplankton structure and dynamics did not seem to be regulated by dissolved salt content in the post-pumping period. [ABSTRACT FROM AUTHOR]