Application of a Weight of Evidence Approach for Monitoring Complex Environmental Scenarios: the Case-Study of Off-Shore Platforms

Multidisciplinary investigations based on integration of chemical and biological measurements, represent an added value to monitoring and management protocols, and their use is recommended by European Directives to evaluate the environmental status of aquatic ecosystems. In this study, a quantitative Weight Of Evidence (WOE) approach, integrating and differently weighting various typologies of data (lines of evidence, LOEs), was applied to validate this approach in assessing the impact of offshore platforms. Using the case-study of an off-shore field monitoring in the Adriatic Sea, procedures are presented to elaborate huge amounts of heterogeneous data from chemical characterization of sediments, bioavailability, biomarkers, ecotoxicological bioassays and benthic communities around 3 platforms. Different typologies of data are initially evaluated within individual modules by logical flowcharts and mathematical algorithms, providing specific hazard indices for each considered LOE, before their overall integration in an environmental risk index. Following specific prescriptions 60 sediment samples were analysed for trace metals, aliphatic hydrocarbons, polycyclic aromatic hydrocarbons, and for the status of benthic communities; bioavailability of metals from sediments was assessed in laboratory conditions on the polychaete Hediste diversicolor, while bioaccumulation of inorganic and organic chemicals and biomarker responses were measured in native and transplanted mussels; ecotoxicological properties of sediments were evaluated through a battery of bioassays determining algal growth of Phaeodactylum tricornutum, bioluminescence of marine bacteria Vibrio fischeri, survival of the copepod Acartia tonsa and embryotoxicity of sea urchin Paracentrotus lividus. Overall, almost 7000 analytical results were elaborated and integration of multiple typologies of data allowed more robust and weighted conclusions compared to the use of individual LOEs, further highlighting the importance of multidisciplinary approaches for an effective monitoring and risk assessment. On a practical side, the WOE evidences also suggested a revision of actual monitoring procedures. The proposed WOE model was confirmed a useful tool to summarize large datasets of complex data in integrative indices, and to simplify the interpretation for stakeholders and decision makers, thus supporting a more comprehensive process of “site-oriented” management decisions.