Abstract

Objective: To test the response of the epiphyte community structure and biomass of the Posidonia oceanica (P. oceanica) leaves to natural disturbance. Methods: Sampling of P. oceanica was carried in winter and summer on three sites in Kuriate Islands (western coast of Tunisia) subject to different environments disturbances. Shoots of P. oceanica were preserved in seawater-formalin (5%) solution for macro-epiphytes species identification in the laboratory. The samples were examined for leaf surface per shoot and the coverage (expressed as a percentage of leaf surface) of each morphological group, then carefully scraped with a razor blade. Epiphytes and scraped leaves were oven-dried at 60 °C for 48 h. Biomass was expressed as g dry weight/shoot. Results: The biomass and the percentage cover of macro-epiphytic leaves showed seasonal variation. The highest values of epiphytic leaves were detected in summer whereas the lowest values were registered during winter. ANOVA showed that Kuriate Islands functioned as a single ecosystem in terms assemblage of macro-epiphytic leaves since no significant variation was detected for biomass and percentage cover at the scale site. Our study showed that natural disturbance had no effect on the assemblage distribution and the biomass of macro-epiphyte on the leaves of P. oceanica between the scales of site, whereas variability at the smallest scale was detected. ANOVA showed that exposure to wind and current had no effect on the biomass of macro-epiphytes leaves. Conclusions: Biomass and assemblages of macro-epiphytic leaves of P. oceanica were high in summer and homogenous between all sites investigated. Natural disturbances such as exposure to wind have no effect on the distribution and the biomass of epiphytes on the shallow meadow.

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