Size distribution approaches for monitoring and conservation of coastal Cymodocea habitats

1.Cymodocea nodosa's leaf length distribution was studied as an easily measurable indicator to monitor and conserve Macedonian, North Aegean, Greek coastal habitats.2.Three Cymodocea meadows off the eastern Kavala Gulf coast (Nea Karvali, Erateino, Agiasma), with that of Nea Karvali close to an industrial area being the most degraded, were sampled during the seagrass main growing season in July 2004. Two further meadows, one pristine to less degraded (Brasidas, Gulf of Kavala) and one degraded (Biamyl, Inner Thessaloniki Gulf), were sampled as benchmarks in July 2005. The results were evaluated using Gaussian fit curves, and non-parametric and nested parametric ANOVA on a hierarchy of spatial scales: area (tens of metres), site (hundreds of metres) and meadow (kilometres).3.Frequency (%) distribution of leaf length values and CymoSkew index variation were best associated with anthropogenic stress. Frequency (%) distribution of adult and intermediate photosynthetic leaf length values revealed a unimodal distribution possible to be fitted, at least at pristine to less degraded meadows, by normal distribution (R²>0.5).4.Statistically significant variation was estimated for CymoSkew index, a quantitative expression of leaf length asymmetry, on the meadow scale (P<0.001). Biamyl (3.82) and Nea Karvali (3.64) were indicated as heavily degraded meadows, Erateino (2.93) as a degraded meadow, Agiasma (2.18) as a meadow with the first signs of degradation, and Brasidas (1.68) as a pristine to less degraded meadow. These results in combination with other meadow specific biotic parameters were used to suggest a preliminary angiosperm 'Ecological Status Classes' classification scheme useful for the implementation of WFD in the north Aegean Sea.5.The CymoSkew index seems to respond to lower levels of stress than is needed for other more conservative plant modules and therefore, could be regarded as an early warning indicator of Cymodocea habitat degradation.