Halophila stipulacea, a seagrass introduced into the Mediterranean Sea as a Lessepsian immigrant, is nowadays common in the eastern Mediterranean, and it was recently recorded in the western Mediterranean; very little information is available about the algal flora associated with this species. During a survey of a Halophila stipulacea stand at Vulcano Island (Eolian Islands, western Mediterranean), samples were collected at three depths (5 m, 15 m and 25 m) for identification of algal epiphytes. Thirty-six species of macroalgae were found. The epiflora of the leaves consisted of 20 species, the others being mixed with or entangled in the rhizomes. On the leaves, Ceramium tenerrimum, Dasya corymbifera, Polysiphonia cfr. tenerrima, Spyridia filamentosa, Chondria pygmaea and Laurencia sp. were the most common species; between the rhizomes, Dictyota linearis was abundant. A differentiation of the epiphytic assemblage between 5 m and the other depths was observed; the 5 m samples were characterized by the abundance of Ceramium tenerrimum, Chondria pygmaea and Polysiphonia cfr. tenerrima, while at 15 m and 25 m Laurencia sp., Dasya corymbifera and Spyridia filamentosa were the most common species. Epiphytic cover was generally very low. No rare species were found among the epiphytes. In comparison with other Mediterranean seagrasses, Halophila stipulacea has a qualitatively and quantitatively poor epiphytic flora. In particular, the virtual absence of encrusting corallines is noteworthy. A fast turnover rate of the leaves is hypothesized to be the main reason for this scarcity. Differences between this and other studies on epiphytes of Halophila stipulacea stands are discussed.
Halophila stipulacea est une phanerogame marine tropicale qui s'est installee en Mediterranee a la suite de l'ouverture du canal de Suez ; a present, elle est commune en Mediterranee orientale et a ete recemment signalee en Mediterranee occidentale. La vegetation algale epiphyte de cette espece est peu connue. Pendant l'etude d'un herbier a Halophila stipulacea de l'ile de Vulcano (les Eoliennes, Mediterranee occidentale) des echantillons ont ete preleves a trois profondeurs differentes (5 m, 15 m et 25 m) pour etudier les epiphytes algaux. Parmi les 36 especes d'algues macroscopiques identifiees dans les releves, 20 constituent l'epiflore des feuilles ; les autres sont entremelees entre les rhizomes. Ceramium tenerrimum, Dasya corymbifera, Polysiphonia cfr. tenerrima, Spyridia filamentosa, Chondria pygmaea et Laurencia sp. sont les algues les plus communes sur les feuilles ; Dictyota linearis est tres abondant entre les rhizomes. Le peuplement epiphyte varie avec la profondeur : les releves effectues a 5 m sont caracterises par l'abondance de Ceramium tenerrimum, Chondria pygmaea et Polysiphonia cfr. tenerrima ; a 15 et 25 m, Laurencia sp., Dasya corymbifera et Spyridia filamentosa sont les especes les mieux representees. Le recouvrement par les epiphytes est tres faible. La flore epiphyte d' Halophila stipulacea, qui ne compte aucune espece rare, apparait quantitativement et qualitativement pauvre par rapport a celle des autres phanerogames mediterraneennes ; cette pauvrete est peut-etre due au renouvellement tres rapide des feuilles. Les differences avec les donnees relatives aux epiphytes d'autres herbiers a Halophila stipulacea sont discutees.