Patterns of phytoplankton diversity in a gradient of Pampean shallow lakes (Argentina) influenced by human activities

Honolulu

Congreso; ASLO Aquatic Sciences Meeting - Mountains to the sea; 2017

American Society of Limnology and Oceanography

The Pampa Region of Argentina has been subjected to an intensification of agriculture and other human interventions during the last decades. In addition, climatic changes with increased rainfall and warmer autumns have been reported for the region. 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 such 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 selected shallow lakes during two years (2013-2014). Our studies indicate that many shallow lakes in the region are prone to the development of algal blooms that include potentially toxic cyanobacteria during the warm season, persisting until autumn. Lakes located in the more impacted zone 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 analyses showed that these two particular lakes had the highest local contribution of beta diversity (LCBD). The highest temporal variation in species richness was observed in a shallow lake located in the floodplain of the large river Paraná, which also exhibited a marked variation in LCBD, being higher in summer.