Diversity and composition of algal epiphytes on the Mediterranean seagrass <i>Cymodocea nodosa</i>: a scale-based study

Abstract Cymodocea nodosa , a typical marine angiosperm species in the Mediterranean Sea, hosts range of epiphytic algae. Epiphyte abundance varies at different spatial scales, yet epiphyte diversity and community composition are poorly understood. This study explores epiphytes on C. from two reference meadows (Thasos, Vrasidas) one anthropogenically stressed meadow (Nea Karvali) northern Aegean Sea (Kavala Gulf, Greece). A nested destructive sampling design three scales (metres, hundreds metres, kilometres) stereoscopic/microscopic observations were used. Light microscopy revealed total 19 taxa macroalgae populating leaves . The most commonly encountered with highest cover (%) Hydrolithon cruciatum Feldmannia mitchelliae DNA sequencing (18S rDNA) confirms presence number dinoflagellate red algal epiphytes, this represents first application metabarcoding to seagrass epiphytes. Epiphytic communities studied species/taxon functional (Ecological Status Groups) levels separated low-stressed degraded one, approach having higher success. ecological evaluation index classified into Ecological Classes according anthropogenic stress.