Abstract
The macroalgae Lophocladia lallemandii (Montagne) F. Schmitz and Sarconema filtforme (Sonder) Kylin and the spaghetti bryozoan Amathia verticillata (delle Chiaje, 1822) are here first reported in native seagrass beds in the Gulf of Gabes (southeastern Tunisia, Mediterranean Sea). Among them, the sighting of S filtforme constitutes the first record of this species in Tunisia. The co-occurrence of these species was observed in the study area with variable abundances, and L. lallemandi appeared to impact the local seagrass meadows of Posidonia oceanica (Linnaeus) Delile. Further studies are needed to monitor the distribution of these non-native and cryptogenic taxa in Tunisia and to confirm or infirm the potential negative impacts of the non-indigenous macroalgae on local biota and seagrass beds.