Influence of temperature on the PICT-response of phototrophic and heterotrophic biofilm communities to copper
Influence de la température sur l'acquisition de tolerance de communautés périphytiques phototrophes et hétérotrophes au cuivre (réponse PICT)
Résumé
The concept of pollution-induced community tolerance (PICT) is a promising tool to establish in the field causal relationship between toxicant exposure and resulting effects. However, for a better application of the PICT-concept, it is important to take into account the influence of abiotic factors on the induction of community tolerance. Accordingly and given the increase in extreme climatic events due to climate change, it is necessary to assess how temperature can modulate the PICT-response following toxicant exposure by affecting the sensitivity of microbial communities. In this aim, we evaluated in microcosms the influence of temperature on the tolerance level of phototrophic and heterotrophic biofilm communities to Cu, according to previous exposure to this metal. Natural biofilms were subjected for 4 weeks to 3 thermal conditions (18°C, 23°C and 28°C) in presence or not of Cu (10 µg/L). Tolerance levels were evaluated using short-term toxicity tests targeting photosynthetic (yield) and heterotrophic enzymatic activities (β-glucosidase, leucine-aminopeptidase and phosphatase). Our results showed a significant influence of temperature on the tolerance levels. However, the magnitude and the direction of the effects of temperature varied according to the Cu exposure history, the kind of communities (phototrophs or heterotrophs), and the functional descriptor considered.