Effects of Experimental Lead Pollution on the Micr

Authors: H NguyenViet D Gilbert E A D Mitchell PM Badot N Bernard

Publish Date: 2007/03/08

Volume: 54, Issue: 2, Pages: 232-241

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Abstract

Ecotoxicological studies usually focus on single microbial species under controlled conditions As a result little is known about the responses of different microbial functional groups or individual species to stresses In an aim to assess the response of complex microbial communities to pollution in their natural habitat we studied the effect of a simulated lead pollution on the microbial community bacteria cyanobacteria protists fungi and micrometazoa living on Sphagnum fallax Mosses were grown in the laboratory with 0 control 625 and 2500 μg L−1 of Pb2+ diluted in a standard nutrient solution and were sampled after 0 6 12 and 20 weeks The biomasses of bacteria microalgae testate amoebae and ciliates were dramatically and significantly decreased in both Pb addition treatments after 6 12 and 20 weeks in comparison with the control The biomass of cyanobacteria declined after 6 and 12 weeks in the highest Pb treatment The biomasses of fungi rotifers and nematodes decreased along the duration of the experiment but were not significantly affected by lead addition Consequently the total microbial biomass was lower for both Pb addition treatments after 12 and 20 weeks than in the controls The community structure was strongly modified due to changes in the densities of testate amoebae and ciliates whereas the relative contribution of bacteria to the microbial biomass was stable Differences in responses among the microbial groups suggest changes in the trophic links among them The correlation between the biomass of bacteria and that of ciliates or testate amoebae increased with increasing Pb loading We interpret this result as an effect on the grazing pathways of these predators and by the Pb effect on other potential prey ie smaller protists The community approach used here complements classical ecotoxicological studies by providing clues to the complex effect of pollutantaffecting organisms both directly and indirectly through trophic effects and could potentially find applications for pollution monitoringWe thank MarieLaure Toussaint for her assistance in Pb analysis Stéphanie Nicopoulos for determining cyanobacterial species and Dominique Rieffel for nematode measurement We express our acknowledgements to Michael Coeurdassier Jérôme Cortet and Renaud Scheifler for giving comments to improve the experimental design and helpful discussion throughout the work Jyrki Jauhianen University of Helsinki Finland Catherine Rausch and Sandrine Gombert Muséum National d’Histoire Naturelle de Paris France are acknowledged for discussion on Sphagnum growth and supplying references on this issue We thank the two anonymous reviewers for helpful comments on an earlier version of the manuscript H NguyenViet has been supported by the University of FrancheComté through a temporary lecturer contract 2004–2006 and by the European Science Foundation through an exchange grant program RSTCB ESF 2006 E Mitchell was at the University of Alaska Anchorage at the onset of this experiment and was later supported by the Swiss contribution to EU project RECIPE no EVK2200200269

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