Studying organic pollutants and sediment bacteria in temporary aquatic environments: the results of a multiple approach.

152 MONDAY 9 SEPTEMBER 2013, 17:30 PS-1. Ecological consequences of global change in aquatic ecosystems PS-1.40. STUDYING ORGANIC POLLUTANTS AND SEDIMENT BACTERIA IN TEMPORARY AQUATIC ENVIRONMENTS: THE RESULTS OF A MULTIPLE APPROACH Annamaria Zoppini, Water Research Institute - National Research Council (IRSA-CNR), Montelibretti, Roma (Italy) Coauthors: Ademollo N, Amalfitano S, Casella P, Patrolecco L, Polesello S Flood and drought events of higher intensity and frequency are expected to increase in arid and semi-arid regions where temporary rivers represent either a water resource or an aquatic ecosystem to be preserved. However, these environments are not recognized in most river management policies. In the present study, we applied a multiple approach characterising the variation of two classes of hazardous substances (Polycyclic Aromatic Hydrocarbons, and NonylPhenols) and the microbial metabolic rates, responsible for organic matter mineralization, in river sediments subject to hydrological fluctuations (Candelaro river basin, Italy). A moderate sediment pollution (PAHs range 8-275 ng g-1; NPs range 299-4858 ng g-1) and drastic changes of the contamination patterns were observed, with mobilization under high flow, accumulation during low flow and a drastic reduction of pollutant concentrations under no flow conditions. The microbial metabolic properties at the streambed level (biomass, bacterial C production, extracellular enzymes, community respiration) declined progressively passing from high flow to low flow conditions, but the resident communities showed residual activities in dry sediments, with potential repercussions on the sediment organic matter quality. The chemical and microbiological dynamics should be taken into consideration for a more realistic prevision of the impact of pollutants in temporary aquatic environments.