In the Mediterranean region Cymodocea nodosa is widely distributed throughout shallow sites. Therefore, a correct assessment of the status of its meadows is of great importance for the implementation of the Water Framework Directive (WFD), the Marine Strategy Framework Directive (MSFD), and the Habitat Directive (HD), especially for areas where Posidonia oceanica meadows (the most frequently used indicator in the Mediterranean Sea) are rare or not present. The previously proposed index for the evaluation of the status of C. nodosa meadows (CymoSkew) is based on ln-transformed relative frequencies of photosynthetic leaf lengths, which we believe is statistically questionable. Therefore, we further improved the methodology and developed a new index named MediSkew, where ln-transformation is applied to raw data of leaf lengths. More specifically, the index is a combination of two metrics, both based on C. nodosa leaf length: deviation from the reference median length (Medi-) and skewness of the length frequency distribution (-Skew), though greater importance was assigned to the first. To develop the classification criteria for the assessment of the status, also a Pressure Index for Seagrass Meadows (PISM), for the evaluation of pressure–impact relationships, was developed. The MediSkew is meant to be a rapid screening method for wide areas, therefore the index should be tested for the assessment of the status of C. nodosa meadows throughout Mediterranean coastal waters. Martina Orlando-Bonaca, Janja Francé, Borut Mavric, Mateja Grego, Lovrenc Lipej, Vesna Flander-Putrle, Milijan Šiško, Annalisa Falace, A new index (MediSkew) for the assessment of the Cymodocea nodosa (Ucria) Ascherson meadow's status, Marine Environmental Research, Volume 110, 2015, Pages 132-141, ISSN 0141-1136, https://doi.org/10.1016/j.marenvres.2015.08.009. (http://www.sciencedirect.com/science/article/pii/S0141113615300374)

Objectives: National water quality monitoring Area: Slovenian sea Attributes: Contaminant concentrations Data sources: ARSO Legal references: Directive 2000/60/EC (WFD), Directive 2008/56/EC (MSFD), Directive 2013/39/EC (EQS-directive) Importance of the work: National level