Paraskevi K Karachle

Maria Corsini Foka

Fabio Crocetta

Jakov Dulčić

Nina Dzhembekova

Marika Galanidi

Petya Ivanova

Noa Shenkar

Marius Skolka

Elitsa Stefanova

Maria Corsini Foka

Kremena Stefanova

Victor Surugiu

Irfan Uysal

Marc Verlaque

Argyro Zenetos

Setting-up a billboard of marine invasive species in the ESENIAS area: current situation and future expectancies

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Biological invasions, both in land and sea, have been worldwide acknowledged as a maninduced ecosystem pressure that should be monitored and managed [START_REF] Roy | Invasive Alien Species -Prioritising prevention efforts through horizon scanning ENV[END_REF][START_REF] Roy | Alien Pathogens on the Horizon: Opportunities for Predicting their Threat to Wildlife[END_REF]. The Mediterranean, has been characterized as a "sea under siege" [START_REF] Galil | A Sea Under Siege -Alien Species in the Mediterranean[END_REF], due to the large number of marine alien species recorded, which are introduced by a variety of pathways/ vectors [START_REF] Zenetos | Alien species in the Mediterranean Sea by 2010. A contribution to the application of European Union's Marine Strategy Framework Directive (MSFD). Part I. Spatial distribution[END_REF](ZENETOS et al., , 2012)). In particular, the Eastern Mediterranean, due to its proximity to the Suez Canal, has been susceptible to biological invasions and hosts more than 775 alien and cryptogenic species (ZENETOS et al., 2012). Similarly, the Black Sea, an enclosed marine system of particular physicochemical characteristics, low diversity and high marine traffic, is vulnerable to marine invasions (LEPPÄKOSKI & MIHNEA, 1996). Of particular importance among aliens are the invasive alien species (IAS), which are considered one of the greatest threats to biodiversity and on ecosystem services (KAT- SANEVAKIS et al., 2014).

Several international agreements such as the Convention on Biological Diversity (CBD), the EU Biodiversity Strategy (EU, 2011), and the European Marine Strategy Framework Directive (EU, 2008), recognise the negative impacts of IAS and highlight the growing concerns of pol-icy-makers, scientists, stakeholders and society.

It is widely acknowledged among scientists that an early warning system should be elaborated, and one of the best ways is through horizon scanning (ESSL et al., 2015; ROY et al., 2015, 2017; and references therein). Horizon scanning is the process of gathering, analysing and disseminating added-value information to support decisionmaking (ROY et al., 2014). However, for most regional seas, lists of current or future biological invasions are not available to date. This is also the case for many countries in the Mediterranean region regarding invasive species in the marine environment. Moreover, it is essential to prioritise IAS, their pathways and the areas of higher likelihood to appear, in order to manage and successfully encounter IAS issues (MCGEOCH et al., 2016).

In the present study, effort has been made to compile a list of marine IAS in the network of the ESENIAS (East and South European Network for Invasive Alien Species) countries, including those species already present in this area and those with a high likelihood of appearance. The aim of this work was to create a catalogue (list of invasive / potential invasive species of ESENIAS concern) to serve as a basis for an early warning system, through a horizon scanning process (ROY et al., 2015). This would allow ESENIAS countries to a) identify the most Of the 160 species comprising the list, 149 were already present in the ESENIAS countries, while eleven were invasive species either present in the Mediterranean or in other European Seas, likely to be recorded in the ESENIAS countries. The majority of the species were of Red Sea/Indo-Pacific origin (97 species; 60.6%). Italy, Turkey and Greece were the countries with the highest representation of species (159, 152 and 139 species respectively), due to their extended coastline and the number of scholars working on marine invasive species. The highest number of established species was recorded in Turkey (116 species), whereas in Italy and Greece the most numerous species were the "expected" ones (85 and 48 species, respectively). The eastern Adriatic Sea countries (i.e. Albania, Croatia, Montenegro and Slovenia) had generally low numbers of species in this list, many of which are still "expected" to arrive from the neighbouring countries of Greece and Italy. Finally, the most frequently potential pathway was transfer stowaways (ship ballast water: 41 cases; ship hull fouling: 55), whereas unaided spread of Lessepsian immigrants followed (95 cases).

This list is intended to serve as an early warning system that through horizon scanning process would assist ESENIAS countries to prioritise invasive alien species, their pathways and the areas of higher likelihood to appear, in order to take management measures.

Key words: invasive species, ESENIAS, Mediterranean Sea, Black Sea harmful species within the ESENIAS area; b) support the establishment of an effective early warning and rapid response mechanisms; c) support any eradication attempts of prioritised species at an early stage of invasion, and d) take management measures for IAS that are already widely spread, as requested by the EU Regulation No 1143/2014 (EU, 2014). Detailed fact sheets of the ten most important species, based on their invasive potential, were also assembled.

MATERIAL AND METHODS

In the framework of ESENIAS-Tools project, a list of invasive/potential invasive species in the ESENIAS countries with marine borders (Albania, Bulgaria, Croatia, Greece, Italy, Montenegro, Romania, Slovenia, and Turkey) was built up. The criteria used for this compilation were the following: a) invasive species already present in the area as reported in the national lists or other literature; b) invasive species in the Mediterranean/Black Sea that have not yet exhibited invasive behaviour in ESENIAS countries and c) invasive species in European Seas, which are likely to invade ESENIAS countries. Cryptogenic species were not considered.

Consequently, based on the existing literature, as well as on expert judgment, the species were classified for the ESENIAS area in the countries as established (species with an already established population in the area), casual (species with just one or few records in the country), invasive (species that are established/invading, with effects -positive and/or negative -on the ecosystem and its services), unknown (species whose presence/status in a country is not yet clarified), and expected (species likely to appear in a country, based on expert judgment and their presence in adjacent areas, and their ecological/ environmental requirements). This latter category was further expanded for Croatia and Italy, as expected in the southern and northern parts of the country. The list also includes the species' origin and potential pathway/vector of introduction (CBD, 2014).

Finally, fact sheets were compiled for ten species that were commonly agreed, among experts, as of high importance. The decision was based on their expanding/invading character according to biological traits and existing data on their invasion history, combined with the absence of published fact sheets at the time (January 2016), excepting Mya arenaria that has recently invaded the Adriatic Sea (CROC- ETTA & TUROLLA, 2011). Each fact sheet includes the following information: a) description and diagnostic features; b) biology and ecology; c) habitat and distribution (both native and in the ESENIAS area); d) pathway/vector of introduction; e) impacts on biodiversity, ecosystem services and human health; and f) risk assessment and management (when applicable). Maps presented here include information until August 2017. The full fact sheets are published at the ESENIAS Scientific Reports (TRICHKOVA et al., 2017), whereas here only a brief account per species is given.

RESULTS AND DISCUSSION

The list of invasive/potential invasive species Overall, 160 species are given in the list, 149 of which are already present in the ESENIAS countries and eleven have not yet been recorded in the area. Approximately two thirds of the species (97 species; 60.6%) were of Red Sea/ Indo-Pacific origin, followed by those of Pacific origin (28 species; 17.5%) (Table A, on-line supplement). From the species included in this list, the countries with the highest representation were Italy, Turkey and Greece (159, 152 and 139 species respectively; Table 1; Table A, on-line supplement; Fig. 1). A plausible explanation could be the fact that these countries have the longest coastlines among the ESENIAS ones, as well as the highest number of marine experts working on invasive species (KARACHLE et al., 2017). Moreover, a recent work on marinas across the Mediterranean has added considerably to the distribution of many invasive species in Turkey, Greece and Italy (ULMAN et al., 2017) Turkey was the country with the highest number of established species (116 species), a fact that it can be attributed to its geographic A B position and proximity to the Suez canal, and, along with Croatia, had the lowest number of expected ones (23 and 24 species, respectively; Table 1; Table A, on-line supplement; Fig. 1). On the other hand, countries with the most numerous expected species were Italy and Greece (85 and 48 species, respectively) followed by Albania, Bulgaria and Romania (31, 31 and 29 species, respectively). In the case of Italy, the high number could be attributed to three main reasons: a) this country is in the middle of the Mediterranean Sea, and hence has influxes of invasive species from both east (mainly Lessepsian immigrants) and west (Atlantic entries); b) intensive oyster activities, mainly in the northern Adriatic, led to accidental transfer of IAS through mariculture, and is thus vulnerable to similar introductions in the future; and c) the country holds major ports and is susceptible to ship transferred species. The last reason stands also for Bulgaria and Romania in the Black Sea. Concerning Greece, it is strongly affected by the Lessepsian invasion, and, due to the proximity to Turkey that holds a substantial number of established alien species, is likely to receive quite many additional IAS. Finally, a small number of species represented in the list characterizes the eastern Adriatic Sea countries, i.e. Albania, Croatia, Montenegro and Slovenia, in general. Yet, all the aforementioned counties display a high number of "expected" IAS, compared to their total IAS. This fact could be related to the low number of experts working on alien species in these countries [START_REF] Karachle | The ESENIAS countries' marine Alien Species experts: an updated inventory[END_REF]. In addition, the neighbouring Greece and Italy display high numbers of alien species (e.g. ZENETOS et al., 2015; MARCHINI et al., 2013; ZENETOS & KARACHLE, 2017), many of which have not been reported to date in the East Adriatic countries (KATSANEVA- KIS et al., 2011).

The vast majority of the listed species (112 species) had only one potential pathway/vector of introduction, while the remaining ones had either two (42 species) or even three (6 species) pathways/vectors (Table A, on-line supplement). In 94 cases species were transferred as stowaways (ship ballast water: 39 cases; ship hull fouling: 55), whereas in 95 cases species were Lessepsian immigrants.

There were only 15 species transported as contaminants on animals (accidentally with aquaculture) and 10 species by other vectors (aquaria intentional releases, aquaculture escapees) (Table A, on-line supplement). It should be noted that invasive cold water species introduced as contaminants in Northern Europe are likely to be introduced to the Black Sea countries and Northern Adriatic but not to the southern countries. In this context, tropical species that are already invasive in the Levantine are more likely to spread in the southern countries but not in the Black Sea.

Species' factsheets: a brief account

Ten species were selected, based on their spreading and invasive character, namely Alexandrium monilatum (J.F.Howell), Bonnemaisonia hamifera Hariot, Streblospio gynobranchiata [START_REF] Rice | Streblospio gynobranchiata, a new spionid polychaete species (Annelida: Polychaeta) from Florida and the Gulf of Mexico with an analysis of phylogenetic relationships within the genus Streblospio[END_REF], Cassiopea andromeda (Forsskål, 1775) ing: 2), whereas P. miles was the only species that had solely been introduced through the Suez Canal (Table A, on-line supplement). There is an expected likelihood of all species to further expand their distribution in the ESENIAS countries, either unaided or through shipping, a possibility that in some cases is medium to high (Table 2). Out of the ten selected species, six have already impacts on the ESENIAS countries, mainly on ecosystems/biodiversity and human health (Table 2), yet they are all expected to have new/additional impacts (Table 2), as in other invasive areas, that should be addressed/ mitigated to the best possible extent.

Alexandrium monilatum (J.F.Howell) Balech (Fig. 2)

Alexandrium monilatum is a thecate, chainforming dinoflagellate. It is a coastal and estuarine planktonic species of warm temperate and tropical environments [START_REF] Taylor | Taxonomy of harmful dinoflagellates[END_REF][START_REF] Steidinger | Dinoflagellates[END_REF]. The species is found in the Atlantic littoral of the USA as follows: Gulf of Mexico [START_REF] Connell | Mass mortality of fish associated with the protozoan Gonyaulax in the Gulf of Mexico[END_REF]RAY & ALDRICH, 1967); Florida [START_REF] Howell | Gonyaulax monilata, sp. nov., the causative dinoflagellate of a red tide on the east coast of Florida in August-September, 1951[END_REF]; Chesapeake Bay [START_REF] May | Effects of the toxic dinoflagellate Alexandrium monilatum on survival, grazing and behavioral response of three ecologically important bivalve mollusks[END_REF]. in the Caribbean Sea: Venezuela [START_REF] Halim | Dinoflagellates of the south-east Caribbean sea[END_REF], and in the tropical Pacific Ocean off Ecuador [START_REF] Balech | The genus Alexandrium Halim (Dinoflagellata)[END_REF]. It was reported for the first time at the Bul-garian coast of the Black Sea in 1991 (MONCHE- VA et al., 1995), where it was also later observed [START_REF] Moncheva | Phytoplankton blooms in Black Sea and Mediterranean coastal ecosystems subjected to anthropogenic eutrophication: similarities and differences[END_REF][START_REF] Nesterova | The State of Phytoplankton[END_REF].

In 2001, the species has been detected also in Odessa port, Ukraine (ANONYMOUS, 2015).

Alexandrium monilatum has been associated with bloom formation [START_REF] Howell | Gonyaulax monilata, sp. nov., the causative dinoflagellate of a red tide on the east coast of Florida in August-September, 1951[END_REF][START_REF] Perry | 1st record of a bloom of Gonyaulax monilata in coastal waters of Mississippi[END_REF][START_REF] Harding | Mortality of the veined rapa whelk, Rapana venosa, in relation to a bloom of Alexandrium monilatum in the York River, United States[END_REF] and fish kills due to ichthyotoxins [START_REF] Gates | The toxicity of Gonyaulax monilata Howell to Mugil cephalus[END_REF]RAY & ALDRICH, 1967). Whole cells and crude extracts of A. monilatum have been shown experimentally to be lethal to mice, rats, fish, shellfish and cockroaches [START_REF] Gates | The toxicity of Gonyaulax monilata Howell to Mugil cephalus[END_REF][START_REF] Aldrich | Gonyaulax monilata: population growth and development of toxicity in cultures[END_REF]CLEMONS et al., 1980a, b;[START_REF] Erker | Acute toxic effects in mice of an extract from the marine algae Gonyaulax monilata[END_REF][START_REF] May | Effects of the toxic dinoflagellate Alexandrium monilatum on survival, grazing and behavioral response of three ecologically important bivalve mollusks[END_REF]. It was reported that A. monilatum produce PSP toxins [START_REF] Hsia | Production of goniodomin A by the planktonic, chain-forming dinoflagellate Alexandrium monilatum (Howell) Balech isolated from the Gulf coast of the United States[END_REF]), yet, to date, the species has not been related to toxic events in the Black Sea. It has been reported in blooming concentration along the Bulgarian Black Sea coast [START_REF] Moncheva | Harmful algae blooms along the Bulgarian Black Sea coast and possible patterns of fish and zoobenthic mortalities[END_REF][START_REF] Moncheva | Phytoplankton blooms in Black Sea and Mediterranean coastal ecosystems subjected to anthropogenic eutrophication: similarities and differences[END_REF]. Blooming species cause water discoloration, especially in late summer, as well as community changes (MONCHEVA & KAMBUR-SKA, 2002;[START_REF] Moncheva | Harmful algae blooms along the Bulgarian Black Sea coast and possible patterns of fish and zoobenthic mortalities[END_REF][START_REF] Moncheva | Phytoplankton blooms in Black Sea and Mediterranean coastal ecosystems subjected to anthropogenic eutrophication: similarities and differences[END_REF][START_REF] Velikova | Phytoplankton dynamics and red tides (1987-1997) in the Bulgarian Black Sea[END_REF]. Other socio-economic effects include beach water aesthetics with a negative impact on recreation [START_REF] Katsanevakis | Impacts of invasive alien marine species on ecosystem services and biodiversity: a pan-European review[END_REF]. Bonnemaisonia hamifera Hariot (Fig. 3)

Bonnemaisonia hamifera is a red alga with a heteromorphic cycle with alternation between a large, coarsely branched gametophyte and a delicate filamentous sporophyte, originally described as a separate species (Trailliella intricata Batters). Native in the North West Pacific, B. hamifera was first recorded in Europe in the British Isles (Dorset) in 1890. The species was probably introduced by shipping. Nowadays, it is widely distributed on southern and western coasts to Shetland Isles, and can be abundant in certain locations, notably where there are large, lagoon-like lower intertidal pools. In the Mediterranean Sea, the first record was as "Trailliella intricata" in 1909 from Tunisia. The gametophytic phase seems to have been observed only in Spain, close to Gibraltar and in Catalonia, whereas the sporophytic phase has been recorded all around the basin (VERLAQUE et al., 2015). Bonnemaisonia hamifera can be found on rocks and on various benthic organisms.

In the north-eastern Atlantic, B. hamifera can have a negative impact as an ecosystem engineer by forming dense epiphytic growth on host algae (JOHANSSON et al., 1998), thus reducing light and nutrient availability for those algae, in addition to preventing competing algae to colonize (SVENSSON et al., 2013). By its high ratio of surface to volume, it has a greater potential for rapid uptake of nutrients in comparison to their host algae (LITTLER & LITTLER, 1980).

Native herbivores strongly preferred native algae to B. hamifera. Bonnemaisonia hamifera produces chemical grazer deterrents, mainly the secondary metabolite 1,1,3,3-tetrabromo-2-heptanone not known from the native algae of the invaded area and the importance of the chemical defence was underlined by the feeding preference of herbivores for B. hamifera individuals with an experimentally depleted content of 1,1,3,3-tetrabromo-2-heptanone (ENGE et al., 2012). Herbivores used B. hamifera as a refuge for fish predation. As a result, the presence of herbivores decreases the performance of neighbouring native algae and increases growth and relative abundance of B. hamifera (ENGE et al., 2013). The 1,1,3,3-tetrabromo-2-heptanone also works as an allelopathic compound that prevents settlement of epiphytic organisms and that can be transferred from B. hamifera to a native host algal species by direct contact, with an active and unaltered function, i.e. in inhibiting recruitment of native competitors (SVENSSON et al., 2013). The secondary metabolite affects the natural fouling community by altering the composition, and changed the diversity by increasing the evenness and decreasing the density, indicating a broad specificity of this metabolite against bacterial colonization (e.g. PERSSON et al., 2011).

Optimal experimental conditions for the biomass production of the sporophytic phase are represented by a combination of temperatures of 15-20°C, photon irradiances of 20-30 µmol photons m -2 s -1 and long daylengths (16:8 h L:D) [START_REF] Nash | Optimum conditions for cultivation of the Trailliella phase of Bonnemaisonia hamifera Hariot (Bonnemaisoniales, Rhodophyta), a candidate species for secondary metabolite production[END_REF]. Fig. 3. Bonnemaisonia hamifera Hariot (left; Photo: Marjan Richter) and its distribution in the Mediterranean Sea [START_REF] Trichkova T | ESENIAS Scientific Reports 2. East and South European Network for Invasive Alien Species -A tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS)[END_REF]. Scale bar=1 cm Cassiopea andromeda (Forsskål, 1775) (Fig. 4)

Cassiopea andromeda is a globally distributed in warm coastal regions semi-sessile, planktonically dispersed scyphomedusa, typically found in shallow lagoons, intertidal sand or mud flats, and around mangroves in Florida, and in the Caribbean. Its native distribution extends from the West Indian Ocean to West Pacific Ocean, and the tropical Atlantic (HOLLAND et al., 2004). The presence of C. andromeda in the Mediterranean Sea dates prior to 1900 (MAAS, 1903).

Cassiopea andromeda is venomous (PALO-MARES & PAULY, 2016) and can kill smaller fish and other marine organisms with which they come into contact, and as such is a threat to the ecosystem functioning. The species might cause an imbalance in a closed area like a bay or lagoon, but its motility is very limited, and is unlikely to spread very much.

Cassiopea andromeda is not highly dangerous because its sting is very mild. Although there has not been any record on hospitalized events of C. andromeda stings, this jellyfish stinging cell can possibly cause discomfort on thin or sensitive skin, as well as the eyes and lips. Moreover, C. andromeda do not normally swim in the water but lie on the bottom with their umbrella facing and touching the substratum and their arms, which are short and shrubby, pointing towards the surface. Swimming over the jellyfish (especially using swim fins) may cause the transparent, essentially invisible, sheets of the mucus to rise in the water column. The stings, appearing in the form of a red rash-like skin irritation, are known for being extraordinarily itchy.

Due to its appearance and nature it may bring people snorkelling or diving into the areas in which the jelly lives, adding to the local economy.

Cassiopea andromeda feeds on copepods, cladocerans, mollusc larvae and on pelagic fish eggs and larvae (PALOMARES & PAULY, 2016). The predation upon fish larvae and eggs could potentially cause impacts on fisheries, especially in the case of consumption of commercial species, yet this is a hypothesis that needs to be further investigated.

No risk assessment analysis on biodiversity, ecosystem services or economy has been conducted. However, its presence in Turkish and Greek coastal areas that are favourite tourist destinations may lead to significant loss of ecosystem services.

Mya arenaria Linnaeus, 1758 (Fig. 5) Mya arenaria is a bivalve that lives burrowed in muddy, sandy and gravelly sediments. It adapts well to a wide range of salinities and temperatures, and can survive both in pristine and disturbed/polluted habitats, including oxygen depleted environments, down to ≥200 m deep.

Archaeological evidence seems to suggest that Mya arenaria originated in the Pacific Ocean during the Miocene, and extended its range in the early Pliocene to the Atlantic. [START_REF] Strasser | Mya arenaria -an ancient invader of the North Sea coast[END_REF][START_REF] Cross | Genetic evidence supports recolonisation by Mya arenaria (L.) of Western Europe from North America[END_REF][START_REF] Lasota | Large-scale mitochondrial COI gene sequence variability reflects the complex colonization history of the invasive soft-shell clam, Mya arenaria (L.) (Bivalvia)[END_REF]. It was also recently sighted in the Mediterranean and Black Sea, including the Turkish Straits (Bosphorus and Marmara Sea), where its presence is confirmed in five ESENIAS countries (Fig. 5). There are no convincing records from the Dardanelles and the Turkish Black Sea so far, presumably due to lack of field studies. Mya arenaria local abundances and establishment success vary within the different ESE-NIAS countries. It is established in the Mediterranean Sea and the Turkish Straits, but with very low abundances and/or restricted ranges except France, where the species spread and become abundant in the Gulf of Lion [START_REF] Zibrowius | Assessing scale and impact of ship transported alien fauna in the Mediterranean?[END_REF][START_REF] Crocetta | Mya arenaria Linné, 1758 (Mollusca: Bivalvia) in the Mediterranean: its distribution revisited[END_REF]. In the Black Sea, soon after its first record from Ukraine (1966) [START_REF] Beshevly | The finding of the mollusc Mya arenaria L. (Bival-via) in the northwestern part of the Black Sea[END_REF], the species established and became dominant in the north western and western parts of the Black Sea, and in the Sea of Azov [START_REF] Zolotarev | The Black Sea ecosystem changes related to the introduction of new mollusc species[END_REF]. On the Bulgarian shelf, M. arenaria is widely distributed on sandy sediments in low salinity waters and at some sites it reaches densities of 4860 individuals m -2 (MARINOV, 1990). In the north western part of the Black Sea it is especially numerous in the coastal zones on muddy sediments, where its biomass exceeds 1 kg m -2 (ZOLOTAREV, 1996).

Mya arenaria impacts vary within the different ESENIAS countries. No impacts have been reported for the Mediterranean and the Turkish Straits, but the taxon shows invasive properties in the Black Sea dominating the soft substratum communities, causing regime shifts and structural changes in native communities/invaded habitats, and affecting sediment and water-column characteristics [START_REF] Katsanevakis | Impacts of invasive alien marine species on ecosystem services and biodiversity: a pan-European review[END_REF].

In its native area, M. arenaria is considered a delicacy, and is harvested by commercial fishery for cookery purposes. On the contrary, to date, the species is not commercially exploited in Europe. It is also a food source for migrating shorebirds and for a wide number of sea inhabitants (fish, sandworms and crabs, among others) [START_REF] Cohen | Guide to the exotic species of San Francisco Bay[END_REF]. As a suspension feeder, it plays a crucial role in filtering and cleaning water sources, and can be used as a tool in regulating and enforcing pollution standards in water quality control. It sequesters carbon in the form of calcium carbonate used for shell creation (KAT- SANEVAKIS et al., 2014). Rice & Levin, 1998 (Fig. 6) Streblospio gynobranchiata is a shallowwater tube-dwelling polychaete species, found in muddy sediments of estuaries, coastal areas and harbours, at depths ranging from 0.5 to 35.6 m, where it forms dense aggregations. CINAR et al. (2005b) reported densities of up to 34,740 individuals m -2 . It prefers the upper layer of the muddy sediments with high levels of organic enrichment, rich in hydrogen sulphide and Seas [START_REF] Trichkova T | ESENIAS Scientific Reports 2. East and South European Network for Invasive Alien Species -A tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS)[END_REF]modified) organic nitrogen [START_REF] Radashevsky | Records of Polydora cornuta and Streblospio gynobranchiata (Annelida, Spionidae) from the Black Sea[END_REF][START_REF] Boltachova | The population dynamics and reproduction of Streblospio gynobranchiata (Annelida, Spionidae), an alien polychaete worm, in the Sevastopol Bay (the Black Sea)[END_REF]. The tolerance of S. gynobranchiata to low concentrations of dissolved oxygen contributes to the colonization of substrates in severely polluted and physically degraded environments. Streblospio gynobranchiata is considered as one of the most successful pioneer and opportunistic species.

Streblospio gynobranchiata

The native distribution area of this species is the western Atlantic [START_REF] Rice | Streblospio gynobranchiata, a new spionid polychaete species (Annelida: Polychaeta) from Florida and the Gulf of Mexico with an analysis of phylogenetic relationships within the genus Streblospio[END_REF][START_REF] Radashevsky | Records of Polydora cornuta and Streblospio gynobranchiata (Annelida, Spionidae) from the Black Sea[END_REF]. It is one of the worst invasive species in the Mediterranean basin, where it was probably introduced via ships ballast waters (ÇINAR et al., 2005a, b). It was first mentioned in the ESENIAS geographic area from the Aegean Turkish littoral (Izmir Bay), where it has been established since 2000 (ÇINAR et al., 2005a, b;2006;[START_REF] Dağli | Spionidae (Annelida: Polychaeta) from the Aegean Sea (eastern Mediterranean)[END_REF]. This species established large and dense populations in the Sea of Marmara (Istanbul area, Golden Horn Estuary, Bosporus Strait; [START_REF] Çinar | Distribution of polychaete species (Annelida: Polychaeta) on the polluted soft substrate of the Golden Horn Estuary (Sea of Marmara), with special emphasis on alien species[END_REF]. It was also reported in the Black Sea [START_REF] Murina | Finding of polychaete Streblospio sp. (Polychaeta: Spionidae) in the Novorossiysk port of the Black Sea (in Russian)[END_REF][START_REF] Boltachova | Finding of new alien species Streblospio gynobranhiata Rice et Levin, 1998 (Polychaeta: Spionidae) in the Black Sea[END_REF]RADASHEVSKY & SELI-FONOVA, 2013;[START_REF] Boltachova | The population dynamics and reproduction of Streblospio gynobranchiata (Annelida, Spionidae), an alien polychaete worm, in the Sevastopol Bay (the Black Sea)[END_REF][START_REF] Teacă | Chapter 7: Assessment of Soft-Bottom Communities and Ecological Quality Status Surrounding Constanta and Mangalia Ports (Black Sea)[END_REF] and the Caspian Sea [START_REF] Taheri | Population changes and reproduction of an alien spionid polychaete, Streblospio gynobranchiata, in shallow waters of the south Caspian Sea[END_REF]. Recently, in 2015, this species was mentioned from the north-eastern part of the Azov Sea, from Taganrog Bay and from the Don River Delta [START_REF] Syomin | Streblospio cf. gynobranchiata (Polychaeta, Spionidae) from the eastern part of Taganrog Bay (in Russian). Зоол. Ж[END_REF].

To date, the impact in the ESENIAS area is a local one, with populations establishing especially in harbour areas and polluted or degraded habitats. The dense populations of the polychaete change the indigenous biocoenoses, especially in polluted soft-bottom benthic habitats (ÇINAR et al., 2005b[START_REF] Çinar | An updated review of alien species on the coasts of Turkey[END_REF].

Dense populations and high biomass of S. gynobranchiata and the position it holds in the food-web as a deposit feeder in areas highly polluted with organic matter have an obvious ecological impact. In such habitats, S. gynobranchiata prove to be a dominant species, as well as a pollution indicator. As a result of the species biology and the large ecological tolerance of S. gynobranchiata, harbour areas with huge traffic and narrow gulfs with muddy bottoms are the most sensitive areas where this spionid polychaete could establish and develop large and dense populations replacing native species. The only measures to avoid the establishment of this species could be maintaining low pollution and eutrophication levels and avoiding discharge of ballast waters in the coastal areas.

Oithona davisae Ferrari & Orsi, 1984 (Fig. 7) Oithona davisae is a pelagic cyclopoid copepod which could be the most abundant mesozooplankton species in its native habitat. It is widely spread around the Black Sea: during the first years the species developed mainly in the coastal waters but now could reach also deep waters above the depth 1000 m. In the coastal and open Black Sea this new Oithona taxon occupied the niche of the disappeared Oithona nana Giesbrecht, 1893 [START_REF] Shiganova | Increase in Findings of Mediterranean Non-native Species in the Black Sea[END_REF].

It is widely accepted that O. davisae is originally endemic to the temperate coastal waters of East Asia and its occurrence in other remote regions is due to anthropogenic introduction, mainly through ballast waters [START_REF] Ferrari | Oithona davisae, new species, and Limnoithona sinensis (Burkckhard, 1912) (Copepoda: Oithonidae) from the Sacramento -San Joaquin Estuary, California[END_REF][START_REF] Nishida | Taxonomy and distribution of the family Oithonidae (Copepoda, Cyclopoida) in the Pacific and Indian Oceans[END_REF][START_REF] Hirakawa | New records of the North Pacific coastal planktonic copepods, Acartia omorii (Acartiidae) and Oithona davisae (Oithonidae) from southern Chile[END_REF]. Oithona Fig. 6. Streblospio gynobranchiata Rice & Levin, 1998 (left;Photo: Natalya A. Boltachova) and its distribution in the Mediterranean and Black Seas (TRICHKOVA et al., 2017) davisae usually inhabits eutrophic embayments [START_REF] Uye | Seasonal reproductive biology of the small cyclopoid copepod Oithona davisae in a temperate eutrophic inlet[END_REF][START_REF] Almeda | Metabolic rates and carbon budget of early developmental stages of the marine cyclopoid copepod Oithona davisae[END_REF] and is indigenous to Japan and the China Seas, and many coastal areas [START_REF] Razouls | Diversity and Geographic Distribution of Marine Planktonic Copepods[END_REF], but it is invasive along the USA west coast [START_REF] Ferrari | Oithona davisae, new species, and Limnoithona sinensis (Burkckhard, 1912) (Copepoda: Oithonidae) from the Sacramento -San Joaquin Estuary, California[END_REF] and the Spanish Mediterranean [START_REF] Saiz | Effects of small-scale turbulence on copepods: The case of Oithona davisae[END_REF]. The invasive successful establishment and expansion of the thermophilic copepod O. davisae in the cold Black Sea is evidence of the extremely high adaptive plasticity of this species. The successful establishment of O. davisae to the Black Sea seems related to phytoplankton structure changes including a prevalence of small flagellates due to climate-driven effects [START_REF] Nesterova | The State of Phytoplankton[END_REF][START_REF] Mavrodieva | Mechanisms of interactions between phytoplankton and marine environmental factors (biotic and abiotic) in the Bulgarian Black Sea coastal waters (Sozopol Bay)[END_REF]. It appears the species has expanded its distribution in the Azov Sea, as it: it has been reported in the Temruk Bay in 2010 [START_REF] Svistunova | A new invader in plankton of the Sea of Azov[END_REF]. At present, O. davisae successfully competes with the larger copepods Acartia tonsa Dana, 1849 and Acartia clausi Giesbrecht, 1889 in the Black Sea. It is still not clear why O. davisae successfully occupied the ecological niche of the disappeared O. nana, while the latter is not successful to return. Because of the specific features of O. davisae, e.g. feeding on flagellates and not on diatoms and detritus, their mass development could affect the abundance of flagellates and bacteria [START_REF] Roff | Bacterivory by tropical copepod nauplii: extent and possible significance[END_REF].

Penaeus aztecus Ives, 1891 (Fig. 8) Penaeus aztecus is a shrimp species, an active swimmer and burrower (SMITHSONIAN MARINE STATION AT FORT PIERCE, 2016), with the juveniles living also in estuarine habitats. It is found from the coastline up to 160 m deep, on muddy or sandy-muddy bottoms, sometimes mixed with sand, clay or broken shells. The adults are mostly active at night, burying in the substrate at daytime (HOLTHUIS, 1980; TAVARES, 2002).

The native distribution of the species is in the western Atlantic (PALOMARES & PAULY, 2016). Penaeus aztecus has also been introduced to New Caledonia and French Polynesia in the 1970s for aquaculture purposes (PALOMARES & PAULY, 2016). The first record of the species in the Mediterranean Sea was in 2009 in Antalya Bay (DEVAL et al., 2010), and by 2013 the species had a well-established population in the area (GÖKOĞLU & ÖZVAROL, 2013; ÖZVAROL & GÖKOĞLU, 2014). Nowadays, P. aztecus has been reported from various areas throughout the Mediterranean, revealing the fast spreading of the species in the basin.

The mode of introduction of P. aztecus in the Mediterranean is still not clear. Some authors consider that it was most likely transferred from the USA through ballast waters (DEVAL et al., 2010; KEVREKIDIS, 2014), whilst more recent discussions (CRUSCANTI et al., 2015; GALIL et al., 2016) suggest that it may be a result of illegal introductions (an aquaculture release/escapee). Yet, both hypotheses need further investigation.

To date, no impacts have been reported for the Mediterranean, but as the species shares the same niche and has similar biological traits with Fig. 7. Oithona davisae Ferrari & Orsi, 1984 (left;Photo: Kremena Stefanova) and its distribution in the Black Sea [START_REF] Trichkova T | ESENIAS Scientific Reports 2. East and South European Network for Invasive Alien Species -A tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS)[END_REF] the indigenous commercial Penaeus kerathurus (Forskål, 1775) [START_REF] Kevrekidis | The occurrence of the Atlantic penaeid prawn Farfantepenaeus aztecus (Ives, 1891) in the Thermaikos Gulf (Aegean Sea, Eastern Mediterranean): considerations on the potential establishment and impact on the autochthonous Melicertus kerathurus (Forskål, 1775)[END_REF][START_REF] Kevrekidis | The Atlantic shrimp Farfantepenaeus aztecus (Ives, 1891): an alien and commercial species in the Greek Seas (in Greek). Hellenic Fishing News[END_REF] the interaction amongst the two species should be monitored and assessed. In the Mediterranean, P. aztecus is caught with both bottom trawlers and trammel nets, along with P. kerathurus. Due to the low catches, it is not yet marketed nor reported separately. Nevertheless, the larger size it can attain compared to that of P. kerathurus, and given the fact that its presence in the catches is constantly increasing [START_REF] Gökoğlu | Biogeographic expansion of Farfantepenaeus aztecus (Ives, 1891) (Decapoda: Penaeidae) in the Eastern Mediterranean Sea. p. 475. In: New Mediterranean Marine biodiversity records (December 2013)[END_REF], may result in its commercial exploitation in the Mediterranean Sea. Yet, the fact that P. aztecus is infested by the parasitic isopod Epipenaeon ingens (Nobili, 1906), combined with the fact that parasitic bopyrid isopods as E. ingens have been found to affect its growth and reproduction (KORUN et al., 2013 and references therein), might lead to a natural control of P. aztecus populations. However, this hypothesis needs to be monitored and further investigated.

Diadema setosum (Leske, 1778) (Fig. 9)

Diadema setosum is a venomous sea urchin (needlespined urchin, long-spined sea urchin) with distinctively delicate hollow spines that inhabits hard substrata, rocks covered with vegetation, and coral reefs. It is widely distributed in the West Indo-Pacific, from the Red Sea, Arabian Gulf, East coast of Africa, to India, Australia and Japan at depths ranging from 0 to 70 m. In the Red Sea, Gulf of Thailand and other native regions, it is the most common sea urchin and one of the most abundant benthic invertebrates. et al., 2017; modified) The tropical sea urchin fauna, which survived the Messinian crisis, but the sudden cooling that started with the Arctic glaciation 2.58 million years ago, led to the end of the tropical fauna of the Mediterranean during the third Pliocene phase (POR, 2009). Yet, Diadema, re-colonized the Mediterranean after an interruption of more than two million years (YOKES & GALIL, 2006). Nowadays, the species is established in the eastern Mediterranean Sea (Fig. 9).

No impact on biodiversity has been reported for the Mediterranean. It is a food source for many reef fishes. The most notable predators of adult sea urchins in the tropical Indo-Pacific are certain large reef fishes, particularly the larger wrasses, triggerfishes, puffers and porcupine fishes. In coral reef aquaria, it offers useful microhabitats to many organisms and it is considered an excellent algae controller. The risk of possible overgrazing phenomena in the ESENIAS countries deserves further study.

Diadema setosum is of medical importance. The species requires particular care when handling or working around it. Its long, slender spines may inflict painful injuries on the unwary swimmers, divers and fishermen. The spines are brittle and hollow, with barbed tips that penetrate the skin and remain imbedded in the flesh, releasing venom from their tissue and lumen. The venom may cause redness, swelling, and acute pain, which subsides after a few hours; however, spine fragments are difficult to remove, and healing may take several weeks [START_REF] Yokes | The first record of the needlespined urchin Diadema setosum (Leske, 1778) (Echinodermata: Echinoidea: Diadematidae) from the Mediterranean Sea[END_REF]. The venom of D. setosum is not at all fatal to humans.

Edible and eaten in some native areas, but it is not very palatable. Diadema setosum is also involved in the marine aquarium trade.

Microcosmus exasperatus Heller, 1878 (Fig. 10) Microcosmus exasperatus is a solitary ascidian with long siphons and leathery bright orange tunic with a few encrustations around the base. It typically attaches to natural and mostly artificial marine hard substrates, forming dense aggregations, which may be heavily fouled by a numerous epibionts.

Microcosmus exasperatus shows a circumtropical distribution, being widely recorded from both the Atlantic and the Indo-Pacific regions, including the Red Sea. According to RAMOS- ESPLA et al. (2013) M. exasperatus was first recorded from Djerba Island (south of Tunisia) in 1998 and then it was observed on the coasts of Lebanon and Israel. It is commonly considered as being a Lessepsian immigrant due to multiple records from its easternmost shores. However, Microcosmus taxa are difficult to be identified, and therefore M. exasperatus worldwide identifications and possible spread patterns may be re-assessed by molecular taxonomy and phylogeography (genbank number: KT387604). Its alien Mediterranean distribution only includes Fig. 10. Microcosmus exasperatus Heller, 1878 (left;Photo: Noa Shenkar) and its distribution in the Mediterranean Sea [START_REF] Trichkova T | ESENIAS Scientific Reports 2. East and South European Network for Invasive Alien Species -A tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS)[END_REF] one ESENIAS country and one main sea (Turkey, Mediterranean Sea), where the taxon is only known on the basis of a single specimen [START_REF] Ramos-Esplá | Microcosmus exasperatus (Ascidiacea: Pyuridae), current distribution in the Mediterranean Sea[END_REF]. Studies that are more recent have revealed that it is established in the region (ME Cinar, unpubl. Info.). However, M. exasperatus was recently recorded from Cyprus [START_REF] Gewing | First record of the non-indigenous ascidian Microcosmus exasperatus, Heller 1878[END_REF], and its known distribution may be easily concealed by taxonomic impediments and low ascidian research effort.

Native Microcosmus taxa are commercially exploited in the Mediterranean and consumed in France, Italy and Greece due to their strong iodine taste. The high nutritional values and the most likely similar taste of the alien taxon would suggest a possible use for culinary purposes. The typical dense populations and heavy epibiont coverage of M. exasperatus may contribute to its establishment as an ecosystem engineer species, as already reported for other worldwide tunicates, and may cause problems when associated with other fouling species.

Pterois miles (Bennett, 1828) (Fig. 11) A tropical marine fish species, Pterois miles is a reef associated species, living depth range 25-85 m, in a variety of habitats, including natural hard bottom, artificial structures, wrecks, bridge pilings, and seagrass (FROESE & PAULY, 2016).

Outside its native range, the species is reported along the southeastern United States coast from Florida to North Carolina, from Bermuda, Bahamas, and is becoming established in the Gulf of Mexico and the Caribbean, including northern South America, and Brazil (SCHOFIELD, 2010; FERREIRA et al., 2015).

In the Mediterranean, a single record from Israel in 1991 (GOLANI & SONIN, 1992), had no follow up for about 20 years. However, a wave of P. miles invasion struck the eastern Mediterranean in the 2010s and is continuing at an increasing rate. In 2012 it was reported from Lebanon (BARICHE et al., 2013), and a year later from Cyprus (EVRIPIDOU, 2013) where, in just one year, it had colonized nearly all of Cyprus' southeastern coast (JIMENEZ et al., 2016). In the following years, the species was sighted in several Mediterranean locations (Fig. 11).

Pterois miles is native to the Indo-Pacific realm (FROESE & PAULY, 2016), and it is thought to have been introduced to the western Atlantic in the mid 1990's by aquarists (HARE & WHITFIELD, 2003). In the Mediterranean, the most likely introduction vector is considered to be the Suez Canal either through ballast water released from vessels crossing the canal (even though globally successful introductions of Scorpaenidae through ballast water have not been reported; see HARE & WHITFIELD, 2003) or by adult migration. However, secondary introductions through additional aquarium release events cannot be ruled out, and genetic connectivity studies are required to trace the origin of the Mediterranean populations. A recent genetic study presents evidence, albeit from a limited sample size, that supports the immigration of a few individuals from the Red Sea via the Suez Canal as the most Fig. 11. Pterois miles (Bennett, 1828) (left; Photo: Gerasimos Kondylatos) and its distribution in the Mediterranean Sea [START_REF] Trichkova T | ESENIAS Scientific Reports 2. East and South European Network for Invasive Alien Species -A tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS)[END_REF]modified) likely introduction mechanism [START_REF] Bariche | Genetics reveal the identity and origin of the lionfish invasion in the Mediterranean Sea[END_REF]).

In the west Atlantic invaded range, lionfish have reached densities that are far higher than those reported from their native range (KUL-BICKI et al,. 2012), exhibit extraordinary predation rates and are having dramatic impacts on the Caribbean ecosystem by displacing native species and disrupting food webs (LESSER & SLAT-ERY 2011; ALBINS 2013).

In the Mediterranean, owing to the young age of the invasion, strong impacts on ecosystems have not been reported yet, as is the case in the invaded Atlantic distribution (for details see ALBINS & HIXON, 2008; LESSER & SLATERY, 2011; GREEN et al., 2012, 2014; ALBINS, 2013; FALETTI et al., 2013; BENKWITT, 2015; BALLEW et al., 2016; PALMER et al., 2016) but are the subject of ongoing research. In addition, the full extent of the socioeconomic damage potentially caused by lionfish is yet to be realised, since the full spectrum and intensity of its ecological impacts and interactions with native species in not fully known.

Pterois miles has a direct impact on human health. The sting from its venomous spines can cause irritation, inflammation, pain and even serious complications in the case of an allergic reaction, putting fishermen, divers and other potential stakeholders at risk. On the other hand, it appears to be very attractive to divers, many of who specifically request dives in areas where the lionfish is known to be present [START_REF] Jimenez | Not everyone's cup of tea: Public perception of culling invasive lionfish in Cyprus[END_REF], at least in the Eastern Mediterranean, where the species is still a novel sighting, similar to what was observed in the Atlantic in the early stages of the invasion. Regardless of its venomous spines, the species is a popular aquarium fish and may create an extra source of income for fishermen who capture and supply the aquarium trade. Moreover, it is consumed in subsistence fisheries in its native area and can provide an alternative fish stock and food source in the invaded range. Its consumption is already promoted in some countries as a means of introducing control measures [START_REF] Nuñez | Invasive Species: To eat or not to eat, that is the question[END_REF].

CONCLUSIONS

This is the first effort to compile a list of marine invasive/potential invasive species in the ESENIAS countries. Such lists are an important initial step for the development of an early warning system, through a horizon scanning process [START_REF] Roy | Invasive Alien Species -Prioritising prevention efforts through horizon scanning ENV[END_REF]. Hence, based on the information presented here identification of future invasions in the ESENIAS countries is possible. It is essential, as a way forward for the countries referred herewith in, to further plan/enforce effective early warning and rapid response mechanisms, as well as take management measures for species that are already widely spread, in compliance with the EU Regulations (EU, 2014). Yet, such a list should be regularly revised and updated so that the management measures enforced would be effective.

Fig. 2 .

 2 Fig. 2. Alexandrium monilatum (J.F.Howell) Balech (left; figure from WALKER & STEIDINGER (1979)) and its distribution in the Black Sea[START_REF] Trichkova T | ESENIAS Scientific Reports 2. East and South European Network for Invasive Alien Species -A tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS)[END_REF]

Fig. 4 .

 4 Fig. 4. Cassiopea andromeda (Forsskål, 1775) (left; Photo: Cemal Turan) and its distribution in the Mediterranean Sea[START_REF] Trichkova T | ESENIAS Scientific Reports 2. East and South European Network for Invasive Alien Species -A tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS)[END_REF] modified)

Fig. 5 .

 5 Fig. 5. Mya arenaria Linnaeus, 1758 (left; Photo: Edoardo Turolla) and its distribution in the Mediterranean and BlackSeas[START_REF] Trichkova T | ESENIAS Scientific Reports 2. East and South European Network for Invasive Alien Species -A tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS)[END_REF] modified)

Fig. 8 .

 8 Fig. 8. Penaeus aztecus Ives, 1891 (left; Photo: Argyro Zenetos & Maria Giavasi) and its distribution in the MediterraneanSea[START_REF] Trichkova T | ESENIAS Scientific Reports 2. East and South European Network for Invasive Alien Species -A tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS)[END_REF]

Table 2 .

 2 Selected features used for horizon scanning and risk assessment, for the ten species that fact sheets were compiled within the ESENIAS-Tools project. AL=Albania,BG=Bulgaria, GR=Greece, HR=Croatia, IT=Italy, ME=Montenegro, RO=Romania, SL=Slovenia, TR=Turkey. VEC= potential vector of expansion, S=shipping, U=unaided,

	RoS= risk of spread, M=Medium, H=high, L=low

Species Presence in ESENIAS countries VEC RoS densities/population explosions Impacts in ESENIAS countries present expected current potential

	toxic event; ecosystem	degradation				invasion in polluted	areas causing ecosystem	degradation	impact on biodiversity	(through predation) and	ecosystem services (e.g.	tourism)	effects on the abundance of	flagellates and bacteria	effects on biodiversity	(competition with the native	Penaeus kerathurus)	invasive in other areas of its	distribution causing effects on	the ecosystem		human health; biodiversity	(through predation) and	ecosystem services (e.g.	tourism)	effects on biodiversity	(biofouling and competition	with other sedentary species)	human health; biodiversity	(through predation)
	impact on ecosystem	(consumption of nutrients,	light decrease)	impact on ecosystem (growth	of other algal species)	impact on ecosystem	(alteration of indigenous	biocoenoses)	impact on human health				replacement of native species	(e.g. Oithona nana)	none to date			invasive in the Black Sea,	causing regime shifts	and changes in the native	communities	none to date				none to date	none to date
	blooms in the Black Sea					high densities in the	Romanian coasts and in	Izmir Bay	high densities in Greece	and Turkey			established populations in	the Black Sea	dense exploitable	populations in Greece and	Turkey	high densities in the Black	Sea			spreading rapidly in	Greece			unknown	increasing populations in	Greece
	M			M/H		M			L				L	M	M			H				M				M	M
	S			S,U		S			U				S		U			U				U				S,U	U
	HR, IT, RO			AL, BG, HR,	ME, RO	BG, IT			AL, HR, ME				IT					HR, SL				IT				GR, IT	AL, ME
	BU			GR, IT, TR		RO, TR			GR, IT, TR				BG, RO, TR		GR, IT, ME, TR			BU, GR, IT, RO,	TR			GR, TR				TR	GR, IT, TR
	Alexandrium	monilatum		Bonnemaisonia	hamifera	Streblospio	gynobranchiata		Cassiopea andromeda				Oithona davisae		Penaeus aztecus			Mya arenaria				Diadema setosum				Microcosmus	exasperatus	Pterois miles

ACKNOWLEDGMENTS

This study was conducted in the frame of the project entitled "East and South European Network for Invasive Alien Species -a tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS)", an EEA funded project (Contract No. Д-33-51/30.06.2015). The authors would also like to thank the following colleagues for providing photos: M. RICHTER (photo of Bonnemaisonia hamifera), C. TURAN (photo of Cassiopea andromeda), E. TUROLLA (photo of Mya arenaria), N.A. BOLTACHOVA (photo of Streblospio gynobranchiata), A. LIAMI (photo of Diadema setosum) and G. KONDYLATOS (photo of Pterois miles). Finally, special thanks to L. FILIPOV for creating the ESENIAS maps, and N.-J. XENTIDIS for the modified maps.


Adriano Sfriso

Marion Adelheid Wolf

Isabella Moro

Andrea A Sfriso

Alessandro Buosi

Marc Verlaque

Adriano Sfriso

M Arion

Adelheid Wolf

Sabella Moro

Andrea A Sfriso

Lessandrob Uosi

&m Arcv Erlaque

Rediscovery of af orgotten Mediterranean Chaetomorpha species in the Venice Lagoon (North Adriatic Sea): Chaetomorpha stricta Schiffner (Cladophorales

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Chaetomorpha Kützing (Cladophorales, Chlorophyta) is ac osmopolitan green algal genus characterized by attached or unattached, unbranched and polynucleate filaments without lateral rhizoids. Members of this taxon occur intertidally in marine and brackish waters (Leliaert &B oedeker,2 007). Most Chaetomorpha species have relatively robust macroscopic thalli, and several species frequently form extensive mats of intertwining filaments that often cause green tides in different regions of the world [START_REF] Flindt | -Loss, growth and transport dynamics of Chaetomorpha aerea and Ulva rigida in the Lagoon of Ve nice during an early summer field campaign[END_REF]Deng et al.,2013;[START_REF] Zhang | -Temporal pattern in the bloom-forming macroalgae Chaetomorpha linum and Ulva pertusa in seagrass beds, Swan Lake lagoon, North China[END_REF]. For example,i nN orth China and Western Australia the massive growth of C. linum (O.F.M ü ller) Kützing mats has replaced other species in some lagoon areas, with an egative impact on seagrass ecosystems and benthic bivalves (Zhang et al.,2 014).

The morphology of this genus is very simple, and only few characters are available to discriminate species, e.g.: attached or unattached growth, filament diameter,s hape and size of the basal cells, length/diameter ratio of cells, presence of constrictions between cells( Leliaert &B oedeker,2 007). For this reason, the taxonomy of Chaetomorpha is very problematic and so far 99 taxa have been reported, of which 70 are currently accepted taxonomically (Guiry &G uiry,2 017). An example of the taxonomic complexity of the genus is illustrated by the species complex containing C. aerea (Dillwyn) Kützing and C. linum,t wo common algae widespread in warm and temperate waters and treated, according to the authors, as only one taxon or two different taxa. In addition to the morphological simplicity and the low number of diagnostic features, phenotypic plasticity,influenced by different environmental factors, can lead to overlapping morphological characters. These considerations highlight the need for molecular data to discriminate among species in the genus Chaetomorpha (Leliaert et al., 2009(Leliaert et al., , 2011)). Several molecular studies, based on gene sequence data of the ribosomal small subunit (SSU) or/and partial large subunit (LSU), were conducted to understand the relationships within Cladophorales ( Bakker et al.,1 994;Hanyuda et al.,2 002;Leliaert et al.,2 003, 2007;Boedeker et al.,2 016).

In this study,w eu sed morphological data coupled with phylogenetic analyses, based on the partial nuclear small subunit (SSU) rDNA, to discriminate a species of Chaetomorpha described from the Ve nice Lagoon (Italy) in the early 20th century and since forgotten: Chaetomorpha stricta Schiffner.

MATERIAL AND METHODS

Sampling and morphological study

The species (hereafter: Va lle Cavallino Chaetomorpha)w as sampled, in May 2011, in Va lle Cavallino during the assessment of the ecological status of the Ve nice Lagoon according to the 2000/60/EC requirements (Fig. 1). The Va lle Cavallino Chaetomorpha was collected both from ab oat with ar ake and manually by SCUBA diving and the associated vegetation was identified. As ubsample was dried in silica gel for genetic analyses and the rest was preserved in 4% formalin/ seawater for the morphological study.Av oucher dried specimen was deposited at the Herbarium Patavinum (PAD) of the University of Padova, Italy,w ith the reference:

-A000622 -Chaetomorpha stricta Schiffner in Schiffner &V atova, collection Adriano Sfriso, Va lle Cavallino (sexagesimal coordinates 45°29'30" N, 12°33'57" E), Ve nice Lagoon, Italy.

The material was comparedw ith two syntypes of C. stricta Schiffner deposited at the Natural History Museum, London (BM), Department of Botany, with the following references:

-000515933 (BM), labeled as Schiffner,A lgae marinae n°232, Chaetomorpha stricta Schiffn. n. sp., Va lP erini, 12.12. The study was completed by comparisons with species of Chaetomorpha deposited at the Herbarium HCOM of the Mediterranean Institute of Oceanography (MIO), Aix-Marseille University,i np articular with the species possessing upper cells with thick and lamellate cell walls:

-C. ligustica (Kützing) Kützing -H8324, coll. Marc Ve rlaque, Sausset-les Pins, France, 23.09.2017, sea level.

-C. pachynema (Montagne) Kützing -H 5634, coll. Marc Ve rlaque, Cala Petraghja, Corsica, 22.08.1992, 3md epth.

Specimens were studied by means of Leica MZ16® and M80® stereo zoom microscopes and Leica 5000® and Optiphot-2 Nikon® light microscopes equipped with adigital image acquisition system. Asubsample of the Va lle Cavallino specimen A000622 was treated according to [START_REF] Moro | -Polyphasic characterization of athermo-tolerant filamentous cyanobacterium isolated from the Euganean thermal muds (Padova, Italy)[END_REF] and studied with a scanning electron microscope FEI Quanta 200® (Oregon, USA). Herbarium abbreviations follow Thiers (2015).

Molecular analyses

Genomic DNA extractions using the Genomic DNA purification kit (Thermo Scientific™)w ere performed on the Va lle Cavallino Chaetomorpha.T he partial SSU gene was amplified using the primer pair SR-4 and 18S-6M (Hanyuda et al., 2002) under the following PCR conditions: initial denaturation step of 94°Cf or 3m in, followed by 35 cycles of 94°Cf or 50 sec, 50°Cf or 50 sec, 72°Cf or 1m in, followed by a final extension of 3min at 72°C. PCR products were cleaned by using the HT ExoSAP-IT (Applied Biosystems™). Sequencing of the amplified fragments was accomplished with the same primer pair at the BMR Genomics Sequencing Service (University of Padova, Italy). The SeqMan II program from the Lasergene software package (DNAStar©,M adison, WI, USA) was used to assemble the final consensus sequence. Since the partial SSU sequences obtained for 9s amples of the Va lle Cavallino Chaetomorpha were all identical, only one was deposited in the International Nucleotide Sequence Database (INSD) through the European Nucleotide Archive (ENA) platform with the following accession number: LT898516.

To infer the phylogenetic position of the Va lle Cavallino Chaetomorpha, a dataset of 16 sequences belonging to different Chaetomorpha species was constructed (Table 1). The genus Siphonocladus F. Schmitz was chosen as outgroup [S. tropicus (P.Crouan &H .Crouan) J.Agardh, accession number AM498761]. Sequences for comparison were downloaded from the USA National Center for Biotechnology Information (NCBI) web server (http://www.ncbi.nlm.nih.gov). Sequence alignment was obtained by the ClustalW computer program (Thompson et al.,1 994). Phylogenetic analyses were performed using the MEGA 5.1 (Molecular Evolutionary Genetics Analysis) program [START_REF] Tamura | -MEGA5 molecular evolutionary genetics analysis using maximum likelihood, evolutionary distance, and maximum parsimony methods[END_REF] according to Neighbour Joining (NJ), Maximum Likelihood (ML), applying the T92 +G+Ievolutionary model [START_REF] Tamura | E stimation of the number of nucleotide substitutions when there are strong transition-transversion and G+Cc ontent biases[END_REF], and Maximum Parsimony (MP) methods. Non-parametricbootstrap re-sampling [START_REF] Felsenstein | C onfidence limits on phylogenies: an approach using bootstrap[END_REF] was performed to test the robustness of the tree topology (1000 replicates).

Bibliographical analysis

Acritical analysis of the literature was conducted to establish the exhaustive list of Chaetomorpha taxa described or reported from the Mediterranean. The diagnostic characters have been researched and critically analysed to identify the current taxonomic status of each taxon. . Filaments free-living (basal cell not observed), light green, 10-20 cm long, entangled to form masses twisted or wrapped around other macrophytes; cells, 250-350 µmb road and 1-2 times as long as broad, with colourless lamellar cell walls, 48-75 µmt hick; filaments frequently covered by calcareous algae, especially Pneophyllum fragile Kützing, cyanobacteria and diatoms belonging to the genus Cocconeis Ehrenberg.

RESULTS

Morphological description of the Valle Cavallino Chaetomorpha

Distribution: The Va lle Cavallino Chaetomorpha was never found in the open lagoon or in other fishing ponds.

Habitat: The Va lle Cavallino Chaetomorpha grew in oligotrophic clear waters of aclosed fishing pond of the northern basin of the Ve nice Lagoon where it formed small entangled masses of filaments within the angiosperm shoots and other macroalgae. The species coexisted with the larger species C. linum,t he only other species of Chaetomorpha recorded in Va lle Cavallino.T he environment of the fishing pond was characterized by high water quality and was prevalently populated by the angiosperms Ruppia cirrhosa (Petagna) Grande and Cymodocea nodosa (Ucria) Ascherson. The macroalgal vegetation of the Va lle Cavallino is mainly composed of Lamprothamnium papulosum (K.Wallroth) J.Groves, as pecies never recorded in the open lagoon, Chaetomorpha linum (O.F.Müller) Kützing, Pneophyllum fragile, Polysiphonia spinosa (C Agardh) J. Agardh, and Va lonia aegagropila C. Agardh. No Ulvaceae were recorded in the area.

DNA sequence available: LT898516 nuclear SSU rDNA. In the phylogeneticr econstruction, theS SU sequence of the Va lle Cavallino Chaetomorpha was placed in aw ell-supported clade (NJ 100%, ML 99%, MP 99% of bootstrap support) with samples belongingtoC. linum and C. aerea from different regions of the world (Fig. 8). The nucleotide divergences of the Va lle Cavallino Chaetomorpha and the sequences of the other specimens are: 0.30% with C. linum (Australia), 0.44% with C. linum (Germany and China) and 0.44% with C. aerea (Germany).

Taxonomic analyses

According to the literature analysed, at otal of 43, 31 and 15 taxa of Chaetomorpha were reported from the Mediterranean Sea, the Adriatic Sea and the Ve nice Lagoon, respectively.A mong them, 8t axa were described from the Ve nice Lagoon (Table 2). [START_REF] Cormaci | -Flora marina bentonica del Mediterraneo: Chlorophyta[END_REF] reduced this list to only 4a ccepted taxa:

-

C. gracilis Kützing -C. ligustica (Kützing) Kützing -C. linum (O.F.M ü ller) Kützing -C. pachynema (Montagne) Kützing
We agree with this treatment, except for two taxa: C. aerea and C. stricta. With regard to the taxonomic status of C. aerea, there are two different viewpoints. Some authors considered the taxon as ag rowth form of C. linum [START_REF] Burrows | Seaweeds of the British Isles[END_REF]John et al.,2003;Leliaert &Boedeker,2007;[START_REF] Mystikou | -New records and observations of macroalgae and associated pathogens from the Falkland Islands, Patagonia and Tierra del Fuego[END_REF], in disagreement with others who reported C. aerea and C. linum as two separate entities [START_REF] Stegenga | Flora van de Nederlandse zeewieren [Flora of the Dutch seaweeds[END_REF][START_REF] Silva | Catalogue of the benthic marine algae of the Indian Ocean[END_REF][START_REF] Sfriso | Chlorophyta multicellulari ef anerogame acquatiche -Ambienti di transizione italiani el itorali adiacenti[END_REF]Brodie et al.,2016;[START_REF] Huang | -Morphological and molecular discrimination of green macroalgae Chaetomorpha aerea and C. linum[END_REF]. The relationship between these species is still uncertain (John et al.,2 003). On this point, [START_REF] Sfriso | Chlorophyta multicellulari ef anerogame acquatiche -Ambienti di transizione italiani el itorali adiacenti[END_REF] highlighted that these taxa should also be considered as distinct entities on the basis of the different habitats they colonize: C. linum grows freefloating in environments covered by seagrasses whereas C. aerea is mostly present in eutrophic environments attached to hard substrata. On the basis of morphological data and ecological requirements, we chose to treat the two taxa separately in the critical review of Chaetomorpha reported in the Mediterranean Sea (Table 2).

Since its description from different parts of the Ve nice Lagoon (Schiffner &V atova, 1937) (Fig. 1), the status of C. stricta has changed over time. The species was successively reported, always without any description, in the Adriatic Sea: Ve nice Lagoon [START_REF] Vatova | -D istribuzione geografica delle alghe nella Laguna veneta ef attori, che la determinano[END_REF], Trieste (Italy) (Pignatti &G iaccone, 1967;[START_REF] Giaccone | Raccolte di fitobenthos sulla banchina continentale Italiana[END_REF], Pianosa Island and Tremiti Islands (Italy) (Rizzi et al.,1 967b;[START_REF] Giaccone | Raccolte di fitobenthos sulla banchina continentale Italiana[END_REF]Rizzi Longo, 1972), Testa del Gargano (Italy) (Rizzi et al.,1 967a;[START_REF] Giaccone | Raccolte di fitobenthos sulla banchina continentale Italiana[END_REF], and Supetarska-Draga (Croatia) (Rizzi Longo, 1972a), and in the Tyrrhenian Sea: Costa dell'Argentario (Italy) (Rizzi Longo, 1972b, as "Chaetomorphastadio stricta Schiffn."). Subsequently, C. stricta was treated as taxon inquirendum (Gallardo et al.,1 993), before being downgraded to ah eterotypic synonym of C. linum (Furnari et al.,1 999, 2003;Cormaci et al.,2 014). The comparison of diagnostic characters of the Va lle Cavallino Chaetomorpha with the protologue of C. stricta and the two C. stricta syntypes deposited at the Natural History Museum, London (Figs 9-14), showed that they belong to the same taxon and that the reduction of C. stricta to ap osterior heterotypic synonym of C. linum was unjustifiable. Chaetomorpha stricta is aspecies that differs very clearly from all the other Mediterranean species in having free-living filaments, 189-370 µmindiameter, with cylindrical cellsand lamellate and thick cell walls up to 90 µmthick (Table 3).

DISCUSSION

As highlighted by other authors, the morphological simplicity,t he low number of diagnostic features and the phenotypic plasticity of species belonging to this genus makes necessary the use of molecular data to discriminate among different entities (Leliaert &B oedeker,2 007; Leliaert et al., 2009Leliaert et al., , 2011)). During the assessment of the ecological status of the Ve nice Lagoon according to the 2000/60/ EC requirements, we collected C. stricta Schiffner,aspecies described from the Ve nice Lagoon in the early 20th century,and subsequently erroneously downgraded to ah eterotypic synonym of C. linum. In the ML tree obtained in this work, the nuclear SSU rDNA sequence of the C. stricta clustered with sequences belonging to two other species present in the lagoon, C. linum and C. aerea,b ut its phylogenetic In the Ve nice Lagoon, the most abundant Chaetomorpha species are C. linum, C. gracilis and C. ligustica that can form blooms reaching many kilograms of biomass per square meter.T he first is especially present in the southern lagoon in association with meadows of angiosperms, whereas C. gracilis and C. ligustica form amixture that colonizesmostly eutrophic and turbid areas. All form long freeliving filaments which can exceed one meter in length. Chaetomorpha aerea is also common in eutrophic and turbid environments, but forms shorter filaments (10-30 cm long) that usually grow attached to hard substrata by al ong basal cell. Although the protologue of C. stricta was based on material collected all around the Ve nice Lagoon, we hitherto observed the species in only one closed fishing pond of the Va lle Cavallino (northern basin); consequently,i tw ould be worth searching for this species in the rest of the Ve nice Lagoon and in other Mediterranean coastal lagoons, especially in the Adriatic Sea.

Key to the Mediterranean

  1930, Commisione Internazionale del Mediterraneo, Ricerche nella LAGUNA VENETA, leg. A. Va tova, 25 May 1937. -BM001044761, labeleda sSchiffner, Algaem arinaen °1 233, Chaetomorpha stricta Schiffn. n. sp., Va lAverto,6.6.1932, Commisione Internazionale del Mediterraneo, Ricerche nella LAGUNA VENETA, leg. A. Va tova, 25 May 1937.

Fig. 1 .

 1 Fig. 1. The Ve nice Lagoon with the sampling site of Va lle Cavallino (STAR) and the six syntype localities of Chaetomorpha stricta Schiffner (Schiffner & Va tova, 1937): 1. Va lle Morosina; 2. Va lA verto; 3. Va lS erraglia; 4. Va lP erini; 5. Isola La Cura; 6. Va lG rassabò.

Fig. 2 .

 2 Fig. 2. Dried specimens (Ref. A000622) of Chaetomorpha stricta Schiffner collected in May 2011i nV alle Cavallino (45.493611°N, 12.566667°E), Ve nice Lagoon. Scale bar = 2c m.

  Figs 3-7. Chaetomorpha stricta Schiffner,( Specimen A000622) Va lle Cavallino, May 2011. 3-4. Filaments with epiphytic calcareous taxa (arrows). 5. Details of cells showing the thick and lamellate cell walls (arrow), 6. Scanning electron microscope image of filaments showing epiphytes (arrows), 7. Detail of epiphytes; arrows: Cocconeis sp.; arrow head: Cyanobacteria. Scale bars: 3&4=400 µm; 5=200 µm; 6=5 00 µm; 7=1 0µ m.

Figs

  Figs 11-14. Syntype BM 000515933 of Chaetomorpha stricta Schiffner. 11. Part of a filament with isodiametric cells. 12. Part of filament with rectangular cells. 13-14. Details of cells showing the thick and lamellate cell walls. Scale bars: 11 &1 2=2 00 µm; 13 =1 00 µm; 14 =5 0µ m.

Chaetomorpha species 1 .

 1 Adult plants fixed; cells cylindrical to barrel-shaped. .........................................2 Adult plants free-living; cells cylindrical ...................................................................3 2. Filaments, up to 3c ml ong and 0.5 to 1m mi nd iameter, fixed by ad igitate holdfast; basal cell 1.5 to 3m ml ong with cell walls 50-100 µmt hick ........ .............................................................. C. pachynema (Montagne) Kützing Filaments, up to 40 cm long and 150-700 µmindiameter, fixed by adiscoidal holdfast; basal cell up to 1.2 mm long with cell walls <3 0µ mthick .......... ............................................................................ C. aerea (Dillwyn) Kützing 3. Cell walls thin .......................................................................................................4 Cell walls thick and lamellate ..............................................................................5 4. Cells <1 00 µm( 24-75 µm) in diameter and 0.5 to 7t imesa sl ong as broad ................................................................................ C. gracilis Kützing Cells >100 µm(120-450 µm, rarely more) in diameter and 0.5 to 3(rarely 5) times as long as broad................................C. linum (O.F.M ü ller) Kützing 5. Cells <1 50 µm( 86-130 µm) in diameter and 0.8 to 2.8 times as long as broad; cell walls 8-20 µmt hick.....................................C. ligustica (Kützing) Kützing Cells >150 µm(189-370 µm) in diameter and 0.5 to 1.6 (rarely 2) times as long as broad; cell walls 30-75 (-90) µmt hick ............................ C. stricta Schiffner

Table 1 .

 1 18S rDNA sequences with accession numbers of Chaetomorpha species downloaded from GenBank for comparison with the Va lle Cavallino Chaetomorpha (accession number: LT898516)

	Taxon	Country of the type locality	Sampling area or country	Accession No.
	C. aerea (Dillwyn) Kützing	England	North Sea, Germany	LT607325
	C. antennina (Bory) Kützing	Réunion	KwaZulu Natal, South Africa LT607328
	C. clavata Kützing	West Indies	Panama	LT607334
	C. coliformis (Montagne) Kützing	Probably Tasmania	Otago, New Zealand	LT607335
	C. firma Levring	Juan Fernandez Isl. Coquimbo, Chile	LT607336
	C. ligustica (Kützing) Kützing	Italy	Zeeland, Netherlands	LT607340
	C. linum (O.F.Müller) Kützing	Denmark	North Sea, Germany	LT607341
	C. linum (O.F.Müller) Kützing	Denmark	Qingdao, China	JN540034
	C. linum (O.F.Müller) Kützing	Denmark	Australia	KT593552
	C. melagonium (F.Weber &D .Mohr)	Sweden	Iceland	LT607342
	Kützing
	C. moniligera Kjellman	Japan	Japan	LT607343
	C. robusta (Areschoug) Papenfuss	South Africa	Cape Town, South Africa	LT607344
	C. spiralis Okamura	Japan	Eastern Cape, South Africa	LT607345

C. valida (J.D.Hooker &H arvey) Kützing

Tasmania

Rongcheng, China JQ308276

C. vieillardii (Kützing) M.J.Wynne New Caledonia Kenya LT607346

Table 2 .

 2 Chaetomorpha species reported from the Ve nice Lagoon, the Adriatic and the Mediterranean Sea according to De Toni &Levi (1888), De Toni Specimens from the Lagoon of Ve nice with filaments very narrow and cells very long included by[START_REF] Sfriso | Chlorophyta multicellulari ef anerogame acquatiche -Ambienti di transizione italiani el itorali adiacenti[END_REF] in the treatment of C. ligustica should be referred to C. gracilis(Cormaci

	Accepted name	or status	C. aerea	(Dillwyn)	Kützing		C. aerea	(Dillwyn)	Kützing	C. aerea	(Dillwyn)	Kützing	C. aerea	(Dillwyn)	Kützing	C. aerea	(Dillwyn)	Kützing	C. aerea	(Dillwyn)	Kützing	C. aerea	(Dillwyn)	Kützing	C. aerea	(Dillwyn)	Kützing ?	C. aerea	(Dillwyn)	Kützing
	Diagnostic characters of	Mediterranean populations	F ixed, cylindrical to slightly	constricted at septa,	150-700 µm, L/D: 0.5 to 2,	cell walls lamellate to thin	m .d., cylindrical, 161 µm,	L/D 0.5 to 1, cell walls thin		F ixed, slightly constricted	at septa, 125-200µm,	L/D: 1.5 to 2, cell walls thin	m .d., constricted at septa,	300-700 µm, L/D: 1t o2 ,	cell walls thin	m .d., constricted at septa,	600-700 µm, L/D: 1,	cell walls thin	F ixed, slightly constricted	at septa, 226-282 µm,	L/D: 1t o1 .5, cell walls thin	F ixed, slightly constricted at	septa, 150-282 µm, L/D:	1t o1 .5, cell walls thin	m .d., barrel-shaped, 732 µm,	L/D: 2, m.d.		Fixed, slightly constricted at	septa, 280-750 µm, L/D: 1,	cell walls thin
	Mediterranean	Sea	X				X			X			X			X			X			X			X			X
	Adriatic	Sea	X				X			-			X			X			-			-			X			X
	Ve nice	Lagoon	X				X			-			X			X			-			-			X			-
	Type locality	Norfolk,	England			Ve nice,	Italy		Algers,	Algeria		Trieste, Ve nice,	Italy and	England	Ve nice,	Italy		Mediterranean	Sea		Marseille,	France		Ve nice,	Italy		Trieste, Italy
	References	Dillwyn, 1806: pl. 80;	Kützing, 1849; 1853,	pl. 59 figs Ia,b		Kützing, 1843: 260;	1845; 1849; 1853, tab;	53 fig. IV	Montagne, 1846: 165;	Kützing, 1849; 1853,	tab; 54 fig. II	C. Agardh, 1824: 99;	Kützing, 1845; 1849;	1853, pl. 59, fig. II	Schiffner &V atova,	1938: 185, pl. XXXII:	fig. 3	Kützing, 1853: 8,	pl. 56: figs 1a,b		Kützing 1847: 167;	1849; 1853, pl. 57,	fig. I	Zanardini, 1847: 255;	1858		Kützing, 1843: 261;	1845; 1849; 1853,	pl.61, figs IIIa-d
	Basionym	Conferva	aerea			Conferva	brachyarthra		Conferva	chlorotica		Conferva	crassa		-			-			-			Conferva	monilina		Conferva	princeps
	Taxon	C. aerea (Dillwyn)	Kützing			C. brachyarthra	(Kützing) Kützing		C. chlorotica	(Montagne) Kützing		C. crassa (C.Agardh)	Kützing		C. crassa f. genuina	Schiffner in Schiffner	&V atova nom. inval.	C. dubyana Kützing			C. herbacea Kützing			C. monilina	(Zanardini) Zanardini		C. princeps (Kützing)	Kützing

(1889)

,

[START_REF] Gallardo | -C heck-list of Mediterranean Seaweeds, II. Chlorophyceae Wille s[END_REF]

,

[START_REF] Furnari | Catalogue of the benthic marine macroalgae of the Italian coast of the Adriatic Sea[END_REF]

,

Leliaert &B oedeker (2007)

,

[START_REF] Sfriso | -Check-list of seaweeds recorded in the last 20 years in Ve nice Lagoon, and ac omparison with the previous records[END_REF]

,

Sfriso et al. (2009)

,

[START_REF] Sfriso | Chlorophyta multicellulari ef anerogame acquatiche -Ambienti di transizione italiani el itorali adiacenti[END_REF]

, Cormaci et al. (2014), Guiry &Guiry (2017) and references in the Table. Diagnostic characters are: (i) plant: free-living or fixed, (ii) cells: cylindrical, slightly constricted at septa, locally swollen or barrel-shaped; (iii) diameter and L/D ratio of cells (iv) cell walls: thin, relatively thick or thick and lamellate. Missing data: m.d. Taxa accepted are in boldface 1

Table 3 .

 3 Diagnostic characters of Mediterranean Chaetomorpha species, with references and data sources is clearly distinct from them. At hird species reported from the lagoon, C. ligustica, is phylogenetically distant from this clade. The nucleotide divergences calculatedb etween C. stricta and the other species of the lagoon are greater than or comparable with the divergences found between other species of the same genus, e.g. C. viellardii -C. antennina (0.15%), C. firma -C. coliformis (0.15%) and C. viellardii -C. clavata (0.44%). These results together with the morphological analyses support the species-level distinction of C. stricta.Currently,s ix species of Chaetomorpha occur in the Mediterranean Sea (see below the Key to the Mediterranean Chaetomorpha species). All of them were reported from the Ve nice Lagoon, except for C. pachynema.

		C. stricta Schiffner in Schiffner &V atova		Schiffner & Syntype Syntype Present study,	Va tova, 1938 BM000515933 BM001044761 specimen A000622	Ve nice Lagoon, Ve nice Lagoon, Ve nice Lagoon, Ve nice Lagoon,	see localities Va lP erini Va lA verto, Va lle Cavallino,	Fig. 1 (12.12.1930) (6.6.1932) (05.2011)		Free-living Free-living Free-living Free-living				Cylindrical Cylindrical Cylindrical Cylindrical		2 00-350 µm, 255-288 µm 1 89-370 µm 2 50-350 µm	usually 250 µm	0.5 to 1.0 0.6 to 1.6 0.6 to 1.5 1.0 to 2.0	(rarely 2.0)	T hick and Thick and Thick and Thick and	lamellate, lamellate, lamellate, lamellate,	ca 30 µm 30-57 µm 41-90 µm 48-75 µm
	C. pachynema	(Montagne)	Kützing	Present study,	specimen H5634	Mediterranean	Sea, Cala	Petraghja, Corsica	(22.08.1992)	Fixed by ab asal	cell >1 .5 mm	long with highly	digitate holdfast	Barrel-shaped		423-919 µm		0.6 to 2.4	Thick, 25-57 µm
	C. linum	(O.F.M ü ller)	Kützing	Cf. references	Table II	Mediterranean	Sea &Atlantic	Ocean		Free-living				Cylindrical		1 20-450 (-752)	µm	(0.5-) 1.0 to 3.0	(-5.0)	Thin
	C. ligustica	(Kützing)	Kützing	Present study,	specimen H8324	Mediterranean	Sea, Sausset-les-	Pins, France	(23.09.2017)	Free-living				Cylindrical		8 6-130 µm		0 .8 to 2.8	Thick and	lamellate,	8-20 µm
	C. gracilis	Kützing	Cf. references	Table II	Mediterranean	Sea			Free-living				Cylindrical		2 4-75 µm		0.5 to 7	Thin
	C. aerea	(Dillwyn)	Kützing	Cf. references	Table II	Mediterranean Sea	&Atlantic Ocean			Fixed by ab asal	cell <1 .2 mm long	with discoid	holdfast	Cylindrical to	barrel-shaped	(125-) 150-750 µm		0.5 to 2.0	Relatively thick	and lamellate	(basal cells) to thin	(upper cells)
					Reference/	source	Locality				Fully-grown	plant			Cells		Diameter		Length/	Diameter ratio	Cell walls

position

Acknowledgements. The authors wish to thank the Herbarium BM and Dr Jo Wilbraham, Senior Curator,Department of Life Sciences, Natural History Museum, London, for sending the two syntypes of C. stricta. The authors also wish to thank Michèle PERRET-BOUDOURESQUE, Mediterranean Institute of Oceanology (Marseille), for documentation assistance, and Michael PAUL for revising the English language.