Characterization of a Cymodocea nodosa (Ucria) Ascherson meadow in the northern Adriatic Sea: phenology, reproduction and epiphytic assemblages

The little Neptune grass Cymodocea nodosa (Ucria) Ascherson is common in shallow coastal areas, lagoons and estuaries in the Mediterranean Sea. As a pioneer and habitat-forming macrophyte, it plays an important ecological role and deserves attention for conservation, especially in areas affected by anthropogenic stressors. A C. nodosa meadow located in a marina of the northern Adriatic Sea (Porticciolo di Torrette, Ancona, Italy) was monitored during its seasonal development (May–October 2024). Structural parameters (shoot density, leaf length and width, percentage of leaves with broken apices), plant fertility and composition of the epiphytic community were assessed across five sampling dates. This population exhibited the typical Mediterranean developmental pattern, with a fully developed canopy in summer (July–September). Female flowers were rarely found, whereas male flowers and fruits were not observed, suggesting that the meadow is likely to rely mainly on clonal propagation. Epiphytic communities displayed low diversity; encrusting corallines and filamentous red algae (Ceramium sp.) were the main algal epiphytes, whereas serpulid polychaetes and ascidiaceans were the main animal epiphytes. Overall, structure, phenology and epiphytic assemblages of the studied meadow are similar to those of other Mediterranean Cymodocea meadows, suggesting that this meadow has persisted under long-term urban conditions despite multiple anthropogenic pressures (not directly tested in the present study).