Acknowledgments The authors would like to thank São Paulo State Research Foundation (FAPESP) for the scholarship to the
first author (2008/56621-5) and financial support (2010/50478-6). In addition, the authors thank Lilian Rodrigues Rosa of University of São Paulo for help in heavy metal analysis. We would also like to thank the working group of Limnology and Plankton Production Laboratory of Aquaculture Center and Marcio Jesus Gonçalves and Mauro Marcelino for technical assistance. We are also grateful to anonymous reviewers for their comments on earlier versions of this manuscript.