Phytoplankton structure variation in five shallow lakes from the Pampean Plain (Argentina)

SÁNCHEZ, M.L.; SCHIAFFINO, M. R.; HUBER, P.; LAGOMARSINO, L.; IZAGUIRRE I.

Kastoria

Workshop; 17th Workshop of the International Association of Phytoplankton; 2014

IAP (International Association of Phytoplankton)

The Salado River basin, located in the Pampean Plain (Argentina), contains thousands of polimyctic shallow lakes that constitute an important wetland, and present different degree of connection with the river. The basin exhibits a high heterogeneity in terms of land use, and the aquatic environments are affected by the different human activities that take place in each zone. In the present study we examined the temporal fluctuations of phytoplankton in five shallow lakes belonging to this basin over a one year period, from October 2012 to September 2013. Among the studied lakes, two (Gómez and El Carpincho) are located upstream from the Salado River basin while the other three lakes (El Triunfo, Salada de Monasterio and Chascomús) are located downstream. We analysed the differences between the lakes of the upper basin and those of the lower basin in relation to land use and urbanization. Whereas all shallow lakes share high conductivity and nutrient concentrations, which is typical of the eutrophic and hypereutrophic water bodies of this region, the phytoplankton communities showed differences in their structure. Both upstream lakes were dominated by Chlorophyceae and showed a similar variation throughout the analyzed period, increasing in abundance after June 2013. Downstream lakes showed a different pattern: Lake Chascomús was dominated by Cyanobacteria and exhibited an increasing trend towards the end of the year; Lake Salada de Monasterio reached a Cyanobacteria peak in the summer that drastically diminished and shifted to a Chlorophyceae dominance; El Triunfo registered high densities of phytoplankton the whole year, which contrasts with observations reported for this lake in previous studies. This research forms part of a long-term Pampean Plain shallow lake monitoring project (PAMPA2 project) and findings offer significant information for the conservation of this valuable wetland.