A new index (MediSkew) for the assessment of the Cymodocea nodosa (Ucria) Ascherson meadow's status

作者：Orlando Bonaca Martina^*; France Janja; Mavric Borut; Grego Mateja; Lipej Lovrenc; Flander Putrle Vesna; Sisko Milijan; Falace Annalisa

来源：Marine Environmental Research, 2015, 110: 132-141.

DOI：10.1016/j.marenvres.2015.08.009

• MediSkew index
• Cymodocea nodosa
• Leaf length
• Assessment of the status
• Mediterranean Sea

In the Mediterranean region Cymodocea nodose 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 In-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 In-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.

• 出版日期2015-9