A Generalization of the TRIX trophic index to the Adriatic Sea basin
Abstract. The Marine Strategy Framework Directive is pushing for new methodological approaches in order to protect the marine environment more effectively. The trophic index TRIX was developed by Vollenweider in 1998 for the coastal area of Emilia-Romagna (northern Adriatic Sea), and was exploited by Italian legislation to characterize the trophic state of coastal waters. In order to implement TRIX in different areas and for different time periods, we developed a methodology for the generalization of the index changing the scaling parameters. We compared the TRIX index calculated from in situ data ("in situ TRIX") with the corresponding index simulated with a coupled physics and biogeochemical numerical model ("model TRIX") implemented in the overall Adriatic Sea. The comparison between in situ and simulated data was carried out for a data time series in the Emilia-Romagna coastal strip. This study demonstrates the compatibility of the model with the in situ TRIX and the necessity to have time series longer than 10 years to evaluate properly the scaling parameters. The model TRIX is finally calculated for the whole Adriatic Sea showing trophic index differences across the Adriatic coastal areas.