Similar Epiphytic Macrofauna Inhabiting the Introduced Sargassum muticum and Native Fucoids on the Atlantic Coast of Morocco

Abstract The diversity and structure of epiphytic macrofaunal assemblages on the introduced invasive brown macroalga Sargassum muticum and native fucoids (Bifurcaria bifurcata, Cystoseira humilis, Cystoseira tamariscifolia and Sargassum vulgare) were compared over a 1-year period in intertidal rockpools on the Atlantic coast of Morocco. In comparison with the epiphytic fauna associated to other macroalgae from European shores, we found that the associated epiphytic macrofauna was moderately diverse (H'<3 bit) and was mainly dominated by gastropods and crustaceans. The most abundant taxa were the isopod Dynamene bidentata and the gastropods Steromphala umbilicalis and Steromphala pennanti. The epiphytic macrofauna community structure differed slightly between the invader and the natives along the year. There was significant temporal variation in the total number of individuals of epiphytic macrofauna per thallus dry weight for the associated epifauna with the highest abundance found on C. tamariscifolia in the spring. The composition of the epiphytic macrofauna on each macroalga species was fairly constant over time. Overall, our results demonstrated that the mobile epiphytic macrofauna on this rocky area showed low macroalgal specificity. They also revealed that the invader S. muticum supports similar epiphytic macrofaunal communities as the native brown macroalgae and provides an additional appropriate habitat for a generalist associated epiphytic macrofauna.