T5 AM Terrestrial Ecotoxicology
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 321-323

(NGU-1117-822445) Effect of lead on microbial communities living in moss: a study under controlled conditions.

Nguyen-Viet, Hung¹, Bernard, Nadine¹, Mitchell, Edward², Badot, Pierre-Marie¹, Gilbert, Daniel¹, ¹ Laboratoire de Biologie Environnementale, USC INRA, EA 3184, Université de Franche-Comté, France., Besançon, France² Laboratoire des Systèmes Ecologiques - LECOS, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland., Lausanne, Switzerland

ABSTRACT- Ecotoxicological studies performed in microcosms have very often focused on the pollutant effect on single species or a small number of microbial species groups. Studying this effect on more complex living structures is necessary to approach the realistic systems. We studied the effect of lead pollution on a large range of microbial communities, which covered bacteria, protists, fungi and micrometazoans living on the moss Sphagnum fallax under controlled conditions. Mosses were grown in the laboratory with 0 (C: control), 625 (treatment E625) and 2500 (E2500) microgram.L-1 of Pb2+ diluted in a standard nutrient solution and were sampled after 0 (T0), 6 (T6), 12 (T12) and 20 (T20) weeks of exposure. Density and biomass of heterotrophic bacteria, testate amoebae and ciliates were dramatically and significantly decreased for E625 and E2500 at T6, T12 and T20 compared to the control. The density and biomass of cyanobacteria, microalgae, fungi, rotifers and nematodes globally decreased along the duration of the experiment but did not significantly diminished compared to the controls except for cyanobacteria of E2500 at T6 and T12. Consequently, the total biomass was lower for E626 and E2500 at T12 and T20 than in the controls. The biomass and density were significantly and negatively correlated with lead concentrations in mosses. Although heterotrophic bacteria remained relatively stable and represented the largest part (mean=45.2%) of the total community biomass whatever the treatment and sampling date, the community structure was heavily shifted by the important changes in testate amoebae and ciliate groups. Species-specific responses to lead pollution were also observed for testate amoebae. A redundancy analysis revealed that lead treatments explained 28.6% of the variation in the microbial community data. This study suggests that microbial communities respond sensitively to lead pollution and therefore, they could be of interest for lead pollution monitoring.

Key words: Lead, Microbial community, Mosses, Bioindication