Organic priority substances and microbial processes in marine coastal sediments (Adriatic Sea, Italy).

PERSEUS EU FP7 Project aims to identify the interacting patterns of natural and human-derived pressures on the Mediterranean and Black Seas, to assess their impact on marine ecosystems and, using the objectives and principles of the Marine Strategy Framework Directive (MSFD) as a vehicle, to design an effective and innovative research governance framework based on sound scientific knowledge. In the frame of this Project (subtask 1.3.3 ADREX: Adriatic and Ionian Seas Experiment), a preliminary monitoring survey has been conducted in the Adriatic Sea (Italy) in order to verify the occurrence and the variation of selected classes of organic priority substances in sediments and to study the structural and functional characteristics of native bacterial communities. The study site represented a good natural laboratory sensitive to climate variability and human pressure, owing to the semi-enclosed nature of the Adriatic Sea and to the increasing trend of human activities in the coastal regions. During the cruise ADRI-13 (November 2013), we sampled three coastal areas nearby Ancona, Gargano Promontory and Bari. Surface sediments were collected in all areas, while sediment cores were sampled in selected sites. The sediment contamination level was determined by measuring the concentration of contaminants included in the list of organic priority substances: PAHs, PCBs, organochlorine pesticides (OCs), bisphenol A (BPA), alkylphenols (Aps), selected on the basis of the anthropogenic pressure. The extraction-clean-up for the PAHs, BPA and Aps was performed by ultrasonic bath with the appropriate solvent, followed by analytical determination with LC-MS and HPLC UV-fluorescence. The extraction of PCBs and OCs was performed by Soxhlet extraction and the concentrated extracts were cleaned-up using acidic silica chromatographic column, followed by determination on GC-ECD. The sediment bacterial abundance was determined by epifluorescence microscopy; the rate of bacterial carbon production was determined by measuring the 3H-leucine uptake rates and the community respiration was estimated by the measurement of the electron transport system (ETS) activity. The analyses of organic pollutants and microbial functional properties in marine sediments described the impact of anthropic pressure on the selected coastal areas. Microbes associated with marine sediments play an important role in the C-flux being responsible for the transformation of organic carbon (autochthonous and allochthonous) into biomass. At the surface layers, the microbial carbon assimilation and mineralization rates were affected by the increasing concentration of pollutants. The higher concentrations of organic pollutants were measured in the deeper sediment analysed (20 cm), along with the reduction of microbial metabolic activities. The results of this study can contribute to acquire information to improve MSFD and to reach the good environmental status.