The state-of-art on alien species in the Mediterranean Sea is presented, making distinctions among the four subregions defined in the EU Marine Strategy Framework Directive: (i) the Western Mediterranean Sea (WMED); (ii) the Central Mediterranean Sea (CMED); (iii) the Adriatic Sea (ADRIA); and (iv) the Eastern Mediterranean Sea (EMED). The updated checklist (December 2010) of marine alien species within each subregion, along with their acclimatization status and origin, is provided. A total of 955 alien species is known in the Mediterranean, the vast majority of them having being introduced in the EMED (718), less in the WMED (328) and CMED (267) and least in the Adriatic (171). Of these, 535 species (56%) are established in at least one area.Despite the collective effort of experts who attempted in this work, the number of introduced species remains probably underestimated. Excluding microalgae, for which knowledge is still insufficient, aliens have increased the total species richness of the Mediterranean Sea by 5.9%. This figure should not be directly read as an indication of higher biodiversity, as spreading of so many aliens within the basin is possibly causing biotic homogenization. Thermophilic species, i.e. Indo-Pacific, Indian Ocean, Red Sea, Tropical Atlantic, Tropical Pacific, and circum(sub)tropical, account for 88.4% of the introduced species in the EMED, 72.8% in the CMED, 59.3% in the WMED and 56.1% in the Adriatic. Cold water species, i.e. circumboreal, N Atlantic, and N Pacific, make up a small percentage of the introduced species, ranging between 4.2% and 21.6% and being more numerous in the Adriatic and less so in the EMED.Species that are classified as invasive or potentially invasive are 134 in the whole of the Mediterranean: 108 are present in the EMED, 76 in the CMED, 53 in the Adriatic and 64 in the WMED. The WMED hosts most invasive macrophytes, whereas the EMED has the lion’s share in polychaetes, crustaceans, molluscs and fish.

This 2010 review of alien species along the coasts of Turkey represents a total of 400 alien species belonging to 14 systematic groups. The present paper also reports the first findings of Vanderhorstia mertensi in the Aegean Sea (Gökova Bay), Chama adspersa in the Sea of Marmara and Mya arenaria in the Aegean Sea. A total of 124 new alien species was determined within the last 5 years. Mollusca had the highest number of species (105 species), followed by Polychaeta (75 species), Crustacea (64 species) and Pisces (58 species). The highest number of alien species (330 species) were encountered on the Levantine coast of Turkey, followed by the Aegean Sea (165 species), Sea of Marmara (69 species) and Black Sea (20 species). The Suez Canal (66% of the total number of alien species) is the main vector for species introductions to the coasts of Turkey, followed by the shipmediated transport (30%). The majority of species (306 species, 76% of total number of species) have become established in the area, while 59 species are classified as casual (15%), 23 species as questionable (6%) and 13 species as cryptogenic (3%). One new alien species was introduced to the coasts of Turkey every 4 weeks between 1991 and 2010. The majority of aliens were found on soft substratum (198 species) in shallow waters (0-10 m) (319 species). Some species such as Caulerpa racemosa, Amphistegina lobifera, Amphisorus hemprichii, Rhopilema nomadica, Mnemiopsis leidyi, Hydroides spp., Ficopomatus enigmaticus, Charybdis longicollis, Rapana venosa, Asterias rubens, Siganus spp. and Lagocephalus sceleratus show a highly invasive character, and have great impacts both on the prevailing ecosystems and humans.

Since 1965, a total of 193 decapod species has been identified from Turkish seas, bringing the number of species to 220 (75 Natantia, 15 M. Reptantia, 36 Anomura, 94 Brachyura). Pandalina profunda and Richardina fredericii are recorded for the first time from the Eastern Mediterranean, and another 8 species (Acantephyra pelagica, Plesionika gigliolii, Stenopus spinosus, Gourretia denticulata, Bathynectes maravigna, Dorhynchus thomsoni, Latreillia elegans, Macropipus tuberculatus) are recorded for the first time from Turkish seas. Kurzfassung. Seit 1965 wurden in den Türkischen Gewässern insgesamt 193 Decapoden-Arten nachgewiesen, womit die Anzahl der Arten nun 220 beträgt (75 Natantia, 15 M. Reptantia, 36 Anomura, 94 Brachyura). Pandalina profunda und Richardina fredericii werden erstmals aus dem östlichen Mittelmeer gemeldet, und weitere 8 Arten (Acantephyra pelagica, Plesionika gigliolii, Stenopus spinosus, Gourretia denticulata, Bathynectes maravigna, Dorhynchus thomsoni, Latreillia elegans, Macropipus tuberculatus) erstmals aus Türkischen Gewässern.

Temporal and spatial variation in soft‐bottom benthic communities following recovery from a pollution episode were studied between January and September 2004 in and around Alsancak Harbor, located in the polluted part of Izmir Bay (Aegean Sea, eastern Mediterranean). Samples were collected at seven stations by van Veen grab. Three additional stations were sampled by means of a beam trawl to take into account large mobile animals and for a better estimate of the local biodiversity. A total of 231 species belonging to 10 zoobenthic groups were found. Polychaetes contributed 90% of the total faunal populations and mollusks 87% of the total biomass in the area. Community parameters varied significantly among stations and sampling periods; number of species ranged from 2 to 79 per 0.1 m2 grab sample; density from 20 to 81,720 ind·m−2; biomass from 0.1 to 4190 g·m−2; Shannon–Wiener diversity index (log2 base) from 0.4 to 4.4; and Pielou's evenness index from 0.11 to 1.0. Collections indicate that a number of species, including those sensitive to pollution, have colonized the area where azoic conditions had been previously reported. A total of six exotic species, Streblospio gynobranchiata, Polydora cornuta, Hydroides dianthus, Hydroides elegans, Anadara demiri and Fulvia fragilis, probably transferred to the area via ballast water or hull fouling, dominated soft or hard substrata in and near Alsancak Harbor. The first two species accounted for more than 70% of the total population in the area, while A. demiri contributed the most to the biomass (93%, at station 7).

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