CS13 Environmental Ecotoxicology
Date: Friday, June 14, 2002
Time: 9:30:00 AM
Location: Esquimalt
 
Garcia-MezaJV, National and Autonomus University of Mexico, Mexico City, Mexico, jviridianagm@correo.unam.mx
Barranguet, C, , University of Amsterdam, Amsterdam, Netherlands, barranguet@science.uva.nl
Duran, C, , National and Autonomus University of Mexico, Mexico City, Mexico, mcduran@servidor.unam.mx
Admiraal, W, , University of Amsterdam, Amsterdam, Netherlands, admiraal@science.uva.nl
 
EFFECT OF METALS ON PHOTOSYNTHESIS, EPS PRODUCTION AND COMPOSITION OF METAL TOLERANT BIOFILMS (GUANAJUATO, MEXICO)
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Biofilms colonize successfully the sediments of a mine-tailings dam (Guanajuato, Mexico),despite the high metals concentration. To elucidate the mechanisms of their metal tolerance,such biofilms were exposed in the lab to Cu (up to 100 uM), Zn (up to1000 uM), and a mixture of both, during five days. The biofilms are composed mainly by chlorophyta (Chlorococcum sp.) and cyanobacteria (Phormidium sp.). Chlorophyll-fluorescence and photosynthetic-efficiency were measured using pulse amplitude modulated (PAM) fluorometry. Minimal fluorescence of dark-adapted cells was obtained with a Phyto-PAM, which allows to discriminate the contribution of different algal groups, and the changes in total biomass and that of each specie. A Water-PAM was used to measure the photosynthetic-efficiency of light-adapted cells. Extracellular polymeric substances (EPS) production was determinated; also metal concentration in EPS. Metal exposure caused: biomass reduction, increasing of EPS production, and Cu and Zn accumulation on EPS in proportion to the concentration in the medium. The predominant species were not per se tolerant and their photosynthetic efficiency and abundance changed. The mechanisms of biofilms tolerance and the immobilisation of metals by the biofilms are discussed.