PROJECT SUMMARY
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.