A new index (MediSkew) for the assessment of the Cymodocea nodosa (Ucria) Ascherson meadow's status.
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.
Marine Biology Station, National Institute of Biology, Fornace 41, 6330 Piran, Slovenia. Electronic address: orlando@mbss.org.
Martina
M
Orlando-Bonaca
Marine Biology Station, National Institute of Biology, Fornace 41, 6330 Piran, Slovenia.
Janja
J
Francé
Marine Biology Station, National Institute of Biology, Fornace 41, 6330 Piran, Slovenia.
Borut
B
Mavrič
Marine Biology Station, National Institute of Biology, Fornace 41, 6330 Piran, Slovenia.
Mateja
M
Grego
Marine Biology Station, National Institute of Biology, Fornace 41, 6330 Piran, Slovenia.
Lovrenc
L
Lipej
Marine Biology Station, National Institute of Biology, Fornace 41, 6330 Piran, Slovenia.
Vesna
V
Flander-Putrle
Marine Biology Station, National Institute of Biology, Fornace 41, 6330 Piran, Slovenia.
Milijan
M
Šiško
Department of Life Sciences, University of Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy.
Annalisa
A
Falace
D035961:Alismatales / Q000033:anatomy & histology*; D003247:Conservation of Natural Resources / Q000379:methods*; D017753:Ecosystem; D008522:Mediterranean Sea; D018515:Plant Leaves / Q000033:anatomy & histology; D017524:Slovenia
Assessment of the status; Cymodocea nodosa; Leaf length; MediSkew index; Mediterranean Sea