U.S.-Brazil Collaborative Research Project: The Production and Fate of Algal Extracellular Polysaccharides in a EutrophicReservoir near São Paulo, Brazil


            The Barra Bonita reservoir receives industrial and domestic sewerage from the city of São Paulo. In the last 15 years, phytoplankton productivity in the reservoir has tripled and eutrophication has dramatically increased as a result of the increasing nutrient input. In the reservoir, only 10 algal species (mainly Cyanobacteria) represent 99% of the species abundance. Blooms of these species affect local water use and impose health risks. In addition, the high particulate load and sedimentation rates threaten to reduce the reservoir lifetime. The main goals of this project are to investigate the ecological functions and environmental implications of algal extracellular polysaccharides (EPS), which are released in great abundance. The project will investigate the following hypotheses:  a) EPS are important substrates for heterotrophic populations; b) EPS contribute to the formation of humic substances; c) EPS are exported outside the reservoir; d) EPS form transparent exopolymer particles (TEP), which represent an important carbon route to the food chain; e) EPS and TEP complex metal ions and constitute important sources of toxic metals to higher trophic levels of the food chain; and f) flocculation of TEP represents an important route of carbon and metals to the sediment and benthic organisms. The results obtained in this project will be used as a basis for eutrophication management, heavy metal contamination management, and water restoration programs in Brazil. Thee results should be generally applicable to similar reservoirs in the U.S. and worldwide. Furthermore, the project will serve to train U.S. and Brazilian personnel and students in limnological and trace metal techniques.