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A preliminary chemical and ecotoxicological assessment was performed on the produced formation water (PFW) and superficial sediment around a gas platform (Fratello Cluster), located in the Adriatic Sea (Italy), in order to evaluate the effects of PFW discharged from the installation. The ecotoxicological bioassays, with the marine bacterium Vibrio fischeri and the sea urchin Paracentrotus lividus, were associated with chemical data to estimate the possible effects on living organisms. PFW collected on the platform was toxic, but no significant effect was recorded on marine sediment. Only the sediment station nearest to the discharge point showed higher values of some contaminants (zinc and arsenic) in comparison to other sites and only some stations showed low toxicity.

European legislative framework supports a multidisciplinary strategy of environmental monitoring because the environment is a complex system of abiotic and biotic interactions, and it should not be studied and protected by looking at one single aspect. The resulting heterogeneous data request to be carefully processed, and the application of Weight of Evidence (WOE) approaches is, thereby, an integrated validated tool. In this perspective, the present study aims to: (i). apply a specific model (Sediqualsoft) based on the WOE approach for processing multidisciplinary data related to four Lines Of Scientific Evidence (LOEs: chemical analyses, ecotoxicological bioassays, bioaccumulation tests and biomarkers) regarding sediments from an area of the Adriatic Sea; (ii). evaluate the usefulness of this specific integrated approach to estimate the potential environmental hazard due to the presence of gas production platforms respect to the traditional approach of sediment chemical characterization. This latter recognized a more contaminated area within 100 m of the platforms in which the Sediqualsoft model showed the presence of a chemical hazard, ranging from moderate to severe, and identified the contaminants (e.g., some metals, benzo(a)pyrene and acenaphthene) most responsible for it. A significant hazard also appeared in some of the sampled stations by analyzing the LOEs dedicated to the biological responses. The choice of different reference values (regulatory limits, threshold values or concentrations measured in the control area) influenced only the chemical hazard but not the overall integration with other LOEs, showing a moderate hazard for the majority of stations. Here, the concentrations measured in a control area are firstly proposed as possible reference values in Sediqualsoft model applications; this could be of particular relevance when Sediment Quality Guidelines are not available for all the measured substances. Moreover, the limitations of a conventional pass-to-fail approach or worst-case scenario were overcoming interpreting whole chemical and ecotoxicological results. All data analyzed and discussed confirm Sediqualsoft as a suitable tool for processing environmental data, including those first processed here on a monitoring scenario of gas platforms that discharge Produced Water into the sea.

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