Effects of anthracene on microbial activities and organic matter decomposition in a Pinus halepensis litter from a Mediterranean coastal area

Due to increasing atmospheric pollution, it has become highly important to investigate how anthropic chronic contaminations may affect ecosystem functioning. To explore the effect of polycyclic aromatic hydrocarbons (PAHs) on indigenous microbial activities, anthracene was used as a model PAH in a mesocosm experiment with Pinus halepensis litter from the Massif of Marseilleveyre (Marseille, France). The effects of anthracene on microbial activities were followed after 1- and 3- month incubations by: Catabolic Level Physiological Profile (CLPP) using ECO and FF plates and four enzyme activities (cellulase, β-glucosidase, acid phosphatase and lipase). Moreover the chemical variations in organic matter were evaluated by solid-state 13C NMR and C/N ratio. These experiments revealed an increase in cellulase, β-glucosidase and phosphatase activities and a decrease in lipase activities after a 3-month incubation in the presence of anthracene. Principal Component Analysis (PCA) from CLPP showed that bacterial catabolic diversity is more influenced than that of fungal communities by anthracene. Correlation between both chemical and biological indicators revealed that the increase in lignocellulolytic enzymes (cellulase, laccase and β-glucosidase) was significantly correlated to the decrease in phenolic compounds. In addition, aromaticity ratio also decreased in the presence of anthracene suggesting that transformation of the recalcitrant part of organic matter was enhanced. Our results highlight the difference in sensitivity of bacterial and fungal communities to PAHs, the later especially active while exposed to high concentrations of pollutant. This suggests that microbial communities inhabiting P. halepensis litters in Mediterranean coastal areas may resist to chronic pollution involving PAH.