Spatio-temporal occurrence patterns of epibiota along the leaves of the seagrass Cymodocea nodosa in the Northern Adriatic Sea

Abstract

We investigated the epibiotic community along Cymodocea nodosa leaves in a seagrass meadow in the Northern Adriatic Sea. In accordance with previous studies, we found that autotrophic organisms dominated throughout the study period (May–October 2014) and showed a clear temporal occurrence pattern with highest occurrence frequencies during summertime. Low relative occurrence of autotrophs was observed in spring, coinciding with higher values for sessile heterotrophs. In both autotrophs and heterotrophs, we observed a general trend towards increased epibiota cover on old leaves and towards the apical (i.e. older) parts of leaves, even though this pattern does not hold true for all species or sampling times. Most heterotrophs were rarely observed, but serpulid polychaetes, the foraminiferan Tretomphaloides concinnus, the hydrozoan Clytia linearis as well as gastropod clutches occurred frequently on all parts of the leaves and showed occurrence patterns putatively reflecting spatial competition with autotrophs and predator avoidance. Hitherto, few data have been available on the epifaunal diversity and community structure on C. nodosa. Thus, this study provides important baseline data for future studies investigating the impact of natural and anthropogenic stressors on epibiota communities associated with this ecologically important Mediterranean seagrass species.