Comparison of epiphyte algal assemblages on the leaves of marine seagrasses Posidonia oceanica (L.) Delile, Cymodocea nodosa (Ucria) Asch, and the lessepsian Halophila stipulacea (Forssk.) Asch in Chebba (East of Tunisia)

This study aims to investigate biometric parameters and epiphytic algae on the leaves of three seagrass species Posidonia oceanica, Cymodocea nodosa, and Halophila stipulacea, which co‐occur in Eastern coast of Tunisia (islet of Kaboudia, Chebba). Sampling was conducted at six stations (5 m depth) during March 2017. Biometrical measurements showed that shoot density and leaf surface area of P. oceanica and the C. nodosa were higher than those of H. stipulacea. Epiphyte covers were correlated with biometric parameters of the three host plants. Epiphyte algal assemblages were more abundant and more diversified on the leaves of P. oceanica and C. nodosa than those on the leaves of H. stipulacea. Significant differences were found for all epiphytic algae groups among the three seagrass species. Seagrass species characteristics (meadow type, shape forms of leaves, life span, and growth rate) seem to be responsible of these dissimilarities in epiphytic algae communities. No apparent negative interactions of H. stipulacea with P. oceanica and C. nodosa have been observed. No invasive epiphytic algae species were found on the leaves of H. stipulacea. It seems that it is a recent installation of H. stipulacea in this area since its density (average 416.23 shoot m−2) was relatively low.