Halophila stipulacea is a dioecious seagrass that colonised the Mediterranean basin probably following the opening of the Suez Canal in 1869. We investigated its occurrence in the southern Mediterranean. This was done by conducting targeted surveys in two countries (Tunisia and Libya) and compiling existing information from former research. Four new meadows of H. stipulacea were found in the study area: Al-wahesh Lagoon and Tobrouk Bay in Libya, and Kerkennah Island-Allama and Cap Monastir in Tunisia. The new record in Cap Monastir (Tunisia) documents a displacement of approximately 150 km north of the previous limit of H. stipulacea in the southern Mediterranean, which probably represents the westernmost extension of H. stipulacea’s distribution 3000 km west along the coast from the site of first colonisation at the mouth of the Suez Canal in Port Said. In the Cap Monastir meadow, the shoot density (±SD) was 9900±3509 m-2and the leaf area index was 3.15±0.5 m2m-2. In Libya, a small meadow of H. stipulacea was documented for the first time in Tobrouk Bay, with an estimated shoot density of 476±83 m-2.
The structure, diversity and spatial distribution of the amphipod fauna associated with Posidonia oceanica meadows were studied along the Tunisian coasts in 2007. Samples were collected in nine diVerent meadows at 2 m depth. A total of 44 species belonging to 12 families were collected. The most common species in terms of abundance were Ampithoe helleri, Hyale camptonyx and Ericthonius punctatus. The highest values of abundance and species richness and the lowest values of diversity and equitability were found in meadows with high epiphyte biomass. Multivariate analyses of data indicated that epiphyte biomass and geographical position were major determinants of the distribution and composition of amphipod assemblages along Tunisian coasts. The presence of two lessepsian amphipod species in one of the southern Posidonia oceanica meadows modiWed the structure of assemblage.
In the present study, the list of alien marine macrophytes introduced into Tunisia was updated in the light of available data and new observations. A total of 27 alien marine macrophytes have been recorded so far from Tunisia: 18 Rhodophyta, 3 Ochrophyta, 5 Chlorophyta and 1 Magnoliophyta. For each species, the locality (-ies), the year (or) period and the source of the first observation in Tunisia are given. The distribution and the status (casual, cryptogenic, established or questionable) of species in Tunisia were evaluated and, where appropriate, discussed. Among them, Hypnea cornuta is reported for the first time from Tunisia. Fourteen alien marine macrophytes are established, whereas seven cryptogenic and two casual species require further investigation. Eleven species are considered as invasive or potentially invasive in the Mediterranean Sea: Acrothamnion preissii, Asparagopsis armata, A. taxiformis Indo-Pacific lineage, Hypnea cornuta, Lophocladia lallemandii, Womersleyella setacea, Caulerpa chemnitzia, C. cylindracea, C. taxifolia, Codium fragile subsp. fragile and Halophila stipulacea. Finally, the case of four questionable species is also discussed.
The presence of marine alien species in El-Kouf National Park and the neighbouring areas was assessed using a compilation of available information and observations, a field survey conducted on October 2010 in the framework of the MedMPAnet project and results of further monitoring during June and September 2012. A total of 9 alien species were reported: the Rhodophyta Asparagopsis taxiformis (Delile) Trevisan de Saint-Léon, the Chlorophyta Caulerpa racemosa var. cylindracea (Sonder) Verlaque, Huisman & Boudouresque, the crab Percnon gibbesi (H. Milne-Edwards, 1853) and the fishes Fistularia commersonii Rüppell, 1838, Siganus luridus (Rüppell, 1829), Siganus rivulatus Forsskål, 1775, Pempheris vanicolensis Cuvier, 1831, Lagocephalus sceleratus (Gmelin, 1789) and Sphyraena flavicauda Rüppell, 1838. Several of them were until now unknown for the National Park. The list of alien marine species of Libya is updated and discussed. Until now 63 marine aliens species were recorded along the Libyan coasts. These include 3 Foraminifera, 3 Ochrophyta, 5 Rhodophyta, 5 Chlorophyta, 1 Magnoliophyta, 11 Arthropoda, 13 Mollusca, 1 Echinodermata and 21 Chordata. Among these Non Indigenous Species, 43 are known as established along the Libyan coast including 8 invasive, 11 casual, 6 questionable, 3 cryptogenic and 1 unknown. An in-depth study of the marine organisms would substantially increase the number of alien species occurring in Libya. Monitoring of marine assemblages of MPAs is a valuable opportunity to go further into the knowledge of native and introduced species.
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