PATTERNS OF PHYTOPLANKTON DIVERSITY IN A GRADIENT OF PAMPEAN SHALLOW LAKES (ARGENTINA) INFLUENCED BY HUMAN ACTIVITIES

IZAGUIRRE I.; CUETO, G.; ZUNINO, J.; O'FARRELL, I.; SCHIAFFINO, M. R.; SÁNCHEZ, M.L.; HUBER, P.

Honolulu

Congreso; ASLO 2017; 2017

ASLO

The Pampa Region of Argentina has been subjected to an intensification of agriculture and other human activities during the last decades. In addition, climatic changes have been reported, with increased rainfall and warmer autumns. These factors are triggering evident changes in the regimes of the shallow lakes, with a tendency to an increase in the number of turbid systems. Under this scenario, in order to analyze the responses of the water bodies to the forcing agents, we are monitoring several shallow lakes of the region across a moisture gradient (mean annual precipitation 1000-500 mm) under the framework of a network project (PAMPA2). We have monthly analyzed the diversity and biomass of phytoplankton in 10 selected shallow lakes of the gradient during two years (2013-2014). Our studies indicate that many shallow lakes in the region are prone to the development of algal blooms, including potentially toxic cyanobacteria during the warm season, persisting until autumn. Lakes located in the more impacted zone of the region have higher phytoplankton abundances and a higher contribution of cyanobacteria. Lowest species richness and phytoplankton abundances were found in two shallow lakes with extreme conditions (high conductivity and high inorganic turbidity). Space-time analyzes showed that the local contribution of beta diversity (LCBD) was higher for these two particular lakes. Highest variation in species richness was observed in a shallow lake located in the floodplain of a large river (Paraná), which also exhibited a marked variation in LCBD, being higher in summer.