Search

Commercial shipping activity plays a crucial role in the unintentional primary and secondary introduction of aquatic Non-Indigenous species (NIS), with ballast water (BW) and hull biofouling being the two major vectors of NIS transportation. The aim of this study is to identify potential high-risk donor port areas that may act as pools for NIS introduction in Saronikos Gulf, Greece. For the purpose of the study, we conducted a regional risk assessment and produced a NIS watch list based on the commercial vessel arrivals at the major ports of the Saronikos Gulf (Piraeus and Elefsis) for the period 2020–2022. In our risk analysis, we used the two most important factors for ship-mediated species introductions identified in the literature: salinity and biogeographic region of the voyage last origin ports. Then, combined with data on vessel arrivals, based on marine traffic data collected from the Marine Traffic online platform, we produced a NIS watch list for the study area. The most highrisk ports for primary introductions were found to be in the Temperate Northern Atlantic (e.g. Gemlik, Ambarli, Asyaport and Derince in Türkiye, Sines in Portugal), Western Indo-Pacific (e.g. Jeddah in Saudi Arabia, Aqaba in Jordan) and the Central Indo-Pacific (e.g. Singapore). For secondary introduction, the most high-risk voyage origin ports are located in the Levantine Sea (e.g. Limassol in Cyprus, Alexandria and Port Said in Egypt, Haifa and Ashdod in Israel, Iskenderun, Mersin and Nemrut in Türkiye), the Aegean Sea (e.g. Izmir in Türkiye) and the Ionian Sea (e.g. Marsaxlokk in Malta). Our watch list included 44 high risk and 13 medium risk NIS to be transferred to Saronikos Gulf. Of these, 38 high-risk species are already present in the Mediterranean, 6 high-risk species are absent from the Mediterranean and 18 species pose a high risk for both primary and secondary introduction. [ABSTRACT FROM AUTHOR]

This work reports on 60 marine alien mollusks from nine countries across the Mediterranean Sea and the Sea of Marmara collected by two Belgian citizen scientists. Some of their published observations concerning collection dates are compared with the year of first publication for these alien mollusks reported in the literature, which enable us to backdate some of their introductions and set new first Mediterranean records for two species. This underlines the importance of collaboration between volunteers and institutional scientists in tracing variations and changes in the environment and biodiversity. [ABSTRACT FROM AUTHOR]

Simple Summary: Human activities and interventions, such as creating sea basin connections (e.g., the Suez Canal), shipping, and aquaculture can serve as pathways for marine species introductions to new ecosystems beyond their natural geographical range. These species are called aliens and may become invasive, negatively impacting the recipient ecosystem. The effective management of invasive species requires understanding and assessing their impacts on the native biota. In this study, we mapped and quantified the cumulative impacts of invasive species on the marine habitats of the Aegean Sea, a Mediterranean ecoregion that is heavily affected by biological invasions. Our findings show that coastal habitats were more impacted by invasive species than the open sea. A higher frequency of strong impacts was observed in the South Aegean compared to the North Aegean, primarily due to alien fish and macrophytes. Shallow hard substrates were the most impacted habitat type, followed by shallow soft substrates and seagrass meadows. The worst invasive species varied depending on the habitat type and impact indicator used. Our study aligns with European guidelines for managing invasive species' impacts on native biodiversity and can serve as an essential tool for managing biological invasions and mitigating their impacts in the Aegean Sea. Biological invasions are a human-induced environmental disturbance that can cause major changes in ecosystem structure and functioning. Located in the northeastern Mediterranean basin, the Aegean Sea is a hotspot of biological invasions. Although the presence of alien species in the Aegean has been studied and monitored, no assessment has been conducted on their cumulative impacts on native biodiversity. To address this gap, we applied the CIMPAL index, a framework developed for mapping the cumulative impacts of invasive species, to identify the most affected areas and habitat types and determine the most invasive species in the region. Coastal areas showed stronger impacts than the open sea. The highest CIMPAL scores were four times more frequent in the South than in the North Aegean. Shallow (0–60 m) hard substrates were the most heavily impacted habitat type, followed by shallow soft substrates and seagrass meadows. We identified Caulerpa cylindracea, Lophocladia lallemandii, Siganus luridus, Siganus rivulatus, and Womersleyella setacea as the most impactful species across their range of occurrence in the Aegean but rankings varied depending on the habitat type and impact indicator applied. Our assessment can support marine managers in prioritizing decisions and actions to control biological invasions and mitigate their impacts. [ABSTRACT FROM AUTHOR]

The current paper presents the first effort to organize a comprehensive review of the Invasive Alien Species (IAS) of Greece. For this purpose, a database was developed with fields of information on the taxonomy, origin, ecology and pathways of introduction of terrestrial, freshwater and marine species. Our database includes a) taxa in the Union's list that are present in Greece, b) taxa already present in Greece and considered to be invasive, and c) taxa highly likely to enter Greece in the next 10 years and become invasive. The Database served as the starting point for the compilation of the National List of Alien Invasive Species (HELLAS-ALIENS) in compliance with the EU Regulation 1143/2014. Overall, the HELLAS-ALIENS comprises 126 species, i.e. 32 terrestrial and freshwater plant species, 14 terrestrial invertebrates, 28 terrestrial vertebrates, 30 freshwater fishes and invertebrates and 22 marine species. Terrestrial invertebrates, birds and mammals are mainly of Asiatic origin. Most of the terrestrial plants have their native geographical distribution in the Americas (North and South). Most of the freshwater invertebrates and fishes are of North American origin, while the majority of the marine species are of Indo-Pacific origin. The first records of IAS concern terrestrial plant species, and date back to the 19th century, while those in freshwater and marine ecosystems seem to have been systematically recorded some decades later. Regarding the pathways of introduction, most of the taxa arrived in Greece or are expected to arrive through escape from confinement and unaided. The majority of the terrestrial, freshwater and marine species have been evaluated as of High-risk for the indigenous biodiversity and only 3% of the species listed have been evaluated of Low-risk. Our results provide an important baseline for management and action plans, as required by the priorities set by the European Union through the Biodiversity Strategy for 2030. [ABSTRACT FROM AUTHOR]

To enrich spatio-temporal information on the distribution of alien, cryptogenic, and neonative species in the Mediterranean and the Black Sea, a collective effort by 173 marine scientists was made to provide unpublished records and make them open access to the scientific community. Through this effort, we collected and harmonized a dataset of 12,649 records. It includes 247 taxa, of which 217 are Animalia, 25 Plantae and 5 Chromista, from 23 countries surrounding the Mediterranean and the Black Sea. Chordata was the most abundant taxonomic group, followed by Arthropoda, Mollusca, and Annelida. In terms of species records, Siganus luridus, Siganus rivulatus, Saurida lessepsianus, Pterois miles, Upeneus moluccensis, Charybdis (Archias) longicollis, and Caulerpa cylindracea were the most numerous. The temporal distribution of the records ranges from 1973 to 2022, with 44% of the records in 2020-2021. Lethrinus borbonicus is reported for the first time in the Mediterranean Sea, while Pomatoschistus quagga, Caulerpa cylindracea, Grateloupia turuturu, and Misophria pallida are first records for the Black Sea; Kapraunia schneideri is recorded for the second time in the Mediterranean and for the first time in Israel; Prionospio depauperata and Pseudonereis anomala are reported for the first time from the Sea of Marmara. Many first country records are also included, namely: Amathia verticillata (Montenegro), Ampithoe valida (Italy), Antithamnion amphigeneum (Greece), Clavelina oblonga (Tunisia and Slovenia), Dendostrea cf. folium (Syria), Epinephelus fasciatus (Tunisia), Ganonema farinosum (Montenegro), Macrorhynchia philippina (Tunisia), Marenzelleria neglecta (Romania), Paratapes textilis (Tunisia), and Botrylloides diegensis (Tunisia). [ABSTRACT FROM AUTHOR]

The Greek Seas are greatly exposed to the proliferation of marine alien species. At least 242 alien species have been reported within Greek territorial waters, three-quarters of which are considered established, while their rate of introduction is increasing. Some of these species exhibit high invasiveness, imposing severe impacts on native ecosystems and ecosystem services. The spatiotemporal proliferation of these species outside their natural boundaries depends on several parameters, including their biological characteristics, native distribution range, introduction pathway, and time of initial introduction. Knowing the current and potential alien species distribution is essential for the implementation of effective management actions. To investigate the distribution of impactful cryptogenic and alien species (ICAS) in the Greek Seas, we combined all records available until the end of 2020 from eight types of data sources: (1) scientific literature, (2) grey literature, (3) offline databases, (4) online scientific databases, (5) personal observations of independent researchers, (6) communications with divers and diving centers, (7) in situ underwater sampling, and (8) social networks. The results of 5478 georeferenced records refer to 60 marine ICAS belonging to 16 taxonomic groups. The number of records and the overall number of ICAS present an increasing trend from the northern to the southern parts of our study area, and there is a clear distinction in community composition between the northern and southern subregions. This latitudinal gradient is mainly due to the large number of thermophilous Lessepsian species of West Indo-Pacific origin, which reach the southern parts of the study area through unaided dispersal. On the other hand, transport stowaways appear to be more prevalent in areas located near large ports, which show significant differences in ICAS numbers and community composition compared to sites located far from ports. Most records (>40% of the total) were associated with rocky reefs, partly reflecting the preference of divers for this habitat type but also the presence of conspicuous, reef-associated impactful fish. The number of published records, as well as the number of reported ICAS, shows a dramatic increase with time, highlighting the urgent need for immediate proactive management actions and scientifically informed control measures. [ABSTRACT FROM AUTHOR]

Invasive alien species are a major worldwide driver of biodiversity change. The current study lists verified records of non-indigenous species (NIS) in European marine waters until 2020, with the purpose of establishing a baseline, assessing trends, and discussing appropriate threshold values for good environmental status (GES) according to the relevant European legislation. All NIS records were verified by national experts and trends are presented in six-year assessment periods from 1970 to 2020 according to the European Union Marine Strategy Framework Directive. Altogether, 874 NIS have been introduced to European marine waters until 2020 with the Mediterranean Sea and North-East Atlantic Ocean hosting most of the introductions. Overall, the number of new introductions has steadily increased since 2000. The annual rate of new introductions reached 21 new NIS in European seas within the last six-year assessment period (2012–2017). This increase is likely due to increased human activities and research efforts that have intensified during the early 21st century within European Seas. As Europe seas are not environmentally, nor geographically homogenous, the setting of threshold values for assessing GES requires regional expertise. Further, once management measures are operational, pathway-specific threshold values would enable assessing the effectiveness of such measures. [ABSTRACT FROM AUTHOR]

Simple Summary: The appearance of a species outside its native area due to human activities (e.g., canal openings, shipping, aquaculture) is described as a biological invasion, and these species are called non-indigenous. The Mediterranean Sea is prone to such an invasion, which is further enhanced by water temperature rising. Moreover, species from the Atlantic further expand their distribution in the Mediterranean, called neonative species, entering through the Gibraltar. Here, we examined the biological traits (e.g., preferred habitat and temperature, length, feeding habits) of fishes present in the Mediterranean Sea, as well as those from the neighboring Atlantic and Red Sea areas, and those that are neonative and non-indigenous in the Mediterranean. We applied state-of-the-art statistical analyses, aiming to describe their biological traits and spot those that could serve as predictors of species that could become neonative and non-indigenous for the Mediterranean. Overall, the results presented here could serve as a baseline for future research, and provide us with a useful tool to plan in advance measures for the protection of native Mediterranean fishes from such invasions. The Mediterranean Sea (MED) is prone to species' introductions, induced by human activities and/or climate change. Recent studies focus on the biological traits that result in such introductions, yet on a single-area-type approach. Here, we used, analyzed, and compared biological traits derived from FishBase for MED, non-indigenous (NIS) and neonative (NEO) in the Mediterranean, and adjacent Atlantic (ATL) and Red Sea (RS) species. A quantitative trait-based analysis was performed using random forest to determine the importance of traits in the successful establishment in the Mediterranean. MED fishes were mainly demersal, slow growing and small-medium sized, preferring intermediate temperatures. Conversely, ATL were mainly deep-dwelling species, preferring low temperatures. RS and NIS were predominantly reef-associated, thermophilus, and stenothermic. NEO species were stenothermic with preference to intermediate-high temperatures. Omnivores with preference to animals was the most common trophic group among regions. MED species exhibited higher phylogenetic uniqueness (PD50) compared to RS and NIS, indicating that they have long ancestral branches and few descendants. Preferred temperature, habitat type preference and maximum reported length (Lmax) and infinite length (Linf) were the most important predictors in the establishment process. Overall, the results presented here could serve as a baseline for future research, especially by using more refined and/or additional biological trail estimates. [ABSTRACT FROM AUTHOR]

Biological invasions have become a defining feature of marine Mediterranean ecosystems with significant impacts on biodiversity, ecosystem services, and human health. We systematically reviewed the current knowledge on the impacts of marine biological invasions in the Mediterranean Sea. We screened relevant literature and applied a standardised framework that classifies mechanisms and magnitude of impacts and type of evidence. Overall, 103 alien and cryptogenic species were analysed, 59 of which were associated with both negative and positive impacts, 17 to only negative, and 13 to only positive; no impacts were found for 14 species. Evidence for most reported impacts (52%) was of medium strength, but for 32% of impact reports evidence was weak, based solely on expert judgement. Only 16% of the reported impacts were based on experimental studies. Our assessment allowed us to create an inventory of 88 alien and cryptogenic species from 16 different phyla with reported moderate to high impacts. The ten worst invasive species in terms of reported negative impacts on biodiversity include six algae, two fishes, and two molluscs, with the green alga Caulerpa cylindracea ranking first. Negative impacts on biodiversity prevailed over positive ones. Competition for resources, the creation of novel habitat through ecosystem engineering, and predation were the primary reported mechanisms of negative effects. Most cases of combined negative and positive impacts on biodiversity referred to community-level modifications. Overall, more positive than negative impacts were reported on ecosystem services, but this varied depending on the service. For human health, only negative impacts were recorded. Substantial variation was found among Mediterranean ecoregions in terms of mechanisms of impact and the taxonomic identity of impacting species. There was no evidence that the magnitude of impact increases with residence time. Holistic approaches and experimental research constitute the way forward to better understanding and managing biological invasions. [ABSTRACT FROM AUTHOR]

In order to assist the implementation of the European policies on Invasive Alien Species (IAS Regulation) and mitigate the impact of alien species that threaten the marine ecosystem services and biodiversity, accurate lists of alien species per European Member State are required. Although inventories of marine alien species and relevant information about them have been reported for the Black Sea marine region of Romania and Bulgaria, a validated list of alien species for the two countries is still lacking. In this paper we (i) propose a validated list of the marine alien species occurring in the Romanian and Bulgarian Black Sea regions, and (ii) address errors, gaps and uncertainties associated with listing alien species from the marine waters of the two countries. The list of alien species includes 37 species for Romania and 26 for Bulgaria, with the highest number of alien species belonging to the phylum Arthopoda for both countries. The majority of alien species have been classified as successfully established in the marine waters of both countries. Thirteen alien species were classified as invasive in Romania whilst eight alien species were classed as invasive in Bulgaria. The historical overview indicates that the number of alien species has steadily increased over the last 50 years both in Romania and Bulgaria. The results of our study provide the baseline list and information for addressing marine alien species at a national level and a starting point for selecting the invasive alien species for risk assessment towards an effective implementation of the IAS Regulation. In conclusion, this study provides supporting information for implementing measures to tackle the introduction of alien species in the western region of the Black Sea. These measures are needed to build an early warning, prevention, and control of invasive alien species in the Black Sea, a unique and fragile ecosystem. [ABSTRACT FROM AUTHOR]

Citizen science (CS) expands the spatial and temporal scale of alien species records. As such, it has been recognized as a complementary tool in alien species management and large‐scale biodiversity conservation. The present study assessed the contribution of CS to the recording of marine alien fishes and mollusks in European marine waters by reviewing data available through the European Alien Species Information Network, portals, public databases, and scientific literature. In total, 8,513 CS records were retrieved, following a filtering procedure, and assessed. A positive relationship was found between CS records and time, with most of records being reported during the last decade. The presence of alien fishes was recorded by citizens in seven out of nine Marine Strategy Framework Directive (MSFD) subregions, while mollusks were recorded in all MSFD subregions. Most of the CS records of fishes were reported in the Mediterranean Sea and mostly in the Aegean‐Levantine Sea. Conversely, most of the CS records of mollusks were reported in NE Atlantic Ocean, mostly in the Greater North Sea. A key finding is that eight species were documented for the first time in European marine waters and other three were recorded outside of their known distribution range. The majority of CS reporting was funneled through scientific surveys in which the nature of CS participation was limited to data collection only. The main categories of citizen scientists included school children, students, divers, naturalists, and various volunteers. Overall, 88.5% of marine alien fishes and mollusks recorded by citizens were validated by taxonomical experts, and only 15.8% out of the validated records were supplemented with pictures. CS can contribute to early detection and enhance cost‐effectiveness of monitoring and surveillance programs regarding alien species in European seas. Still, it requires proper scientific support and adequate validation tools mechanisms. [ABSTRACT FROM AUTHOR]

Biological invasions represent one of the main threats to marine biodiversity. From a conservation perspective, especially in the context of increasing sea warming, it is critical to examine the suitability potential of geographical areas for the arrival of Range‐Expanding Introduced and Native Species (REINS), and hence anticipate the risk of such species to become invasive in their new distribution areas. Here, we developed an empirical index, based on functional and bio‐ecological traits, that estimates the Invasive Potential (IP; i.e. the potential success in transport, introduction and population establishment) for a set of 13 fishes that are expanding their distributional range into the Mediterranean Sea, the most invaded sea in the world. The IP index showed significant correlation with the observed spreading of REINS. For the six species characterized by the highest IP, we calculated contemporary and future projections of their Environmental Suitability Index (ESI). By using an ensemble modelling approach, we estimated the geographical areas that are likely to be the most impacted by REINS spreading under climate change. Our results demonstrated the importance of functional traits related to reproduction for determining high invasion potential. For most species, we found high contemporary ESI values in the South‐eastern Mediterranean Sea and low to intermediate contemporary ESI values in the Adriatic Sea and North‐western Mediterranean sector. Moreover, we highlighted a major potential future expansion of high ESI values, and thus REINS IP, towards the northern Mediterranean, especially in the northern Adriatic Sea. This potential future northward expansion highlights the risk associated with climate‐induced impacts on ecosystem conservation and fish stock management throughout the entire Mediterranean Sea. [ABSTRACT FROM AUTHOR]

The Atlantic blue crab Callinectes sapidus is a portunid native to the western Atlantic, from New England to Uruguay. The species was introduced in Europe in 1901 where it has become invasive; additionally, a significant northward expansion has been emphasized in its native range. Here we present a harmonized global compilation of C. sapidus occurrences from native and non-native distribution ranges derived from online databases (GBIF, BISON, OBIS, and iNaturalist) as well as from unpublished and published sources. The dataset consists of 40,388 geo-referenced occurrences, 39,824 from native and 564 from non-native ranges, recorded in 53 countries. The implementation of quality controls imposed a severe reduction, in particular from online databases, of the records selected for inclusion in the dataset. In addition, a technical validation procedure was used to flag entries showing identical coordinates but different year of record, in-land occurrences and those located close to the coast. Similarly, a flagging system identified entries outside the known distribution of the species, or associated with unsuccessful introductions. Measurement(s) geographic location Technology Type(s) digital curation Factor Type(s) location • year of record Sample Characteristic - Organism Callinectes sapidus Sample Characteristic - Environment marine biome Sample Characteristic - Location Globe Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.14077112 [ABSTRACT FROM AUTHOR]

Shipping is the greatest pathway of non-indigenous species (NIS) introductions, and port areas are considered as alien hotspots. In this study, we analyzed data covering a 112-year period and found that Saronikos Gulf in Greece, hosting one of the largest container port terminals in Europe, is a hotspot of NIS introductions. To date, 89 NIS have been recorded, of which 8 are characterized as invasive. Most species belong to the taxonomic group of Mollusca (33%), followed by Pisces (22%). For the first time in the Mediterranean Sea, we report the presence of the micromolluscs Sinezona plicata (Hedley, 1899) and Ringicula sp. Moreover, we provide evidence for the trend of NIS introduction in the Saronikos Gulf across the past 70 years, the pathways of introduction and their importance through time, as well as the distribution of the most invasive species in the Saronikos Gulf. The information provided herein can assist the implementation of the EU Marine Strategy Framework Directive and inform NIS management. As Transport-Stowaway remains the main pathway of NIS introduction in the Saronikos Gulf, our principal recommendation is to reinforce regulations for the adoption of better antifouling practices and more effective ballast water treatment and management. [ABSTRACT FROM AUTHOR]

The number of alien species arriving within new regions has increased at unprecedented rates. Managing the pathways through which alien species arrive and spread is important to reduce the threat of biological invasions. Harmonising information on pathways across individual sectors and user groups is therefore critical to underpin policy and action. The European Alien Species Information Network (EASIN) has been developed to easily facilitate open access to data of alien species in Europe. The Convention on Biological Diversity (CBD) Pathway Classification framework has become a global standard for the classification of pathways. We followed a structured approach to assign pathway information within EASIN for a subset of alien species in Europe, which covered 4169 species, spanning taxonomic groups and environments. We document constraints and challenges associated with implementing the CBD Pathway Classification framework and propose potential amendments to increase clarity. This study is unique in the scope of taxonomic coverage and also in the inclusion of primary (independent introductions to Europe) and secondary (means of dispersal for species expansion within Europe, after their initial introduction) modes of introduction. In addition, we summarise the patterns of introduction pathways within this subset of alien species within the context of Europe. Based on the analyses, we confirm that the CBD Pathway Classification framework offers a robust, hierarchical system suitable for the classification of alien species introduction and spread across a wide range of taxonomic groups and environments. However, simple modifications could improve interpretation of the pathway categories ensuring consistent application across databases and information systems at local, national, regional, continental and global scales. Improving consistency would also help in the development of pathway action plans, as required by EU legislation. [ABSTRACT FROM AUTHOR]

The distribution of marine life has been alarmingly reshaped lately and the number of non-indigenous species and their impacts are rapidly escalating globally. Timely and accurate information about the occurrence of non-indigenous species are of major importance for the mitigation of the issue. However, still large gaps in knowledge about marine bioinvasion exist. Mediterranean Sea is among the most impacted ecoregions globally. In this work we present a comprehensive overview of the project "Is is Alien to you? Share it!!!" which monitors non-indigenous species in Greece and Cyprus with the help of citizen scientists. The goal of this work is to present this project as a case study in order to demonstrate how citizen science can substantially contribute to the monitoring of biological invasions. We compared the projects database with the databased of ELNAIS and EASIN, for discuss weaknesses and advantages and future steps for advancing the effort. In total 691 records of marine alien and cryptogenic species were collected in these 2 years from Greece and Cyprus, with the density of records reaching 20 observations per km2 in some locations. The project has contributed significantly in the assessment of descriptor D2 "Exotic Species" of the Marine Strategy Framework Directive, with 3 new species for Greece. Future steps should focus on training citizens to report less reported taxa and raising the awareness of all relevant stakeholders. [ABSTRACT FROM AUTHOR]

Invasive alien species (IAS) are one of the major drivers of change that can negatively affect biodiversity, ecosystem functions and services and human health; islands are particularly vulnerable to biological invasions. Horizon scanning can lead to prioritisation of IAS to inform decision-making and action; its scale and scope can vary depending on the need. We focussed on IAS likely to arrive, establish and affect biodiversity and human health on the Mediterranean island of Cyprus. The scope of the horizon scanning was the entire island of Cyprus. We used a two-step consensus-building process in which experts reviewed and scored lists of alien species on their likelihood of arrival, establishment and potential to affect biodiversity, ecosystems and/or human health in the next 10 years. We reviewed 225 alien species, considered to be currently absent on Cyprus, across taxa and environments. We agreed upon 100 species that constituted very high, high or medium biodiversity risk, often arriving through multiple pathways of introduction. The remaining 125 species were ranked as low risk. The potential impacts on human health were documented for all 225 species; 82 species were considered to have a potentially negative impact on human health ranging from nuisance to disease transmission. The scope of the horizon scanning was the entire island of Cyprus, but the thematic groups also considered the relevance of the top 100 species to the Sovereign Base Areas of Cyprus, given their differing governance. This horizon scan provides the first systematic exercise to identify invasive alien species of potential concern to biodiversity and ecosystems but also human health within the Mediterranean region. The process and outcomes should provide other islands in the region and beyond with baseline data to improve IAS prioritisation and management. [ABSTRACT FROM AUTHOR]

This work presents a current (2018) annotated list of marine NIS and cryptogenic species in Greek marine waters. For this purpose, we updated information from previous lists, included new data from several new NIS and cryptogenic records and recent taxonomic studies, and followed current taxonomic modifications for the alien/cryptogenic status of several introduced species. Our extensive literature survey and revisions resulted in the exclusion of 61 species, which were included in previous lists, and the addition of 41 new alien species reported in the 2016-2018 period plus ten old NIS records. The current number of introduced species in Greek waters whose presence is not questionable includes 214 alien species and 62 cryptogenic species. Approximately 80% of the introduced species in Greek Seas consists of the taxa--in decreasing order--Mollusca, Polychaeta, Crustacea, Fishes, and Macroalgae. Nevertheless, a considerable increase in the number of NIS Bryozoa and Ascidiacea was observed within the last decade. Unaided natural dispersal of Lessepsian immigrants (57%) and transport-stowaways (36.7%) are the major pathways of introduction reported for Greek waters. However, with few exceptions (6.8% of species), the confidence level in assigning a pathway was medium to low. Several species reported from adjacent marine areas are expected to reach Greek waters within the next years. The intensification of underwater observations by citizen scientists combined with further research in hot spot areas, understudied habitats and overlooked taxa will significantly raise the number of NIS species in Greek waters. This study can serve as a basis that could greatly benefit from the coordination and harmonization of monitoring initiatives under international, EU and Regional Policies, and the compilation of new data from established monitoring programs, and rapid assessment surveys. [ABSTRACT FROM AUTHOR]

In this study, we have performed a large-scale assessment on the native distribution range of the marine non-indigenous species (NIS) found in at least one of the European Seas (Mediterranean, NE Atlantic Ocean, Black, Baltic Sea). As a basis, we have used the most updated pan-European NIS inventory, provided by the European Alien Species Information Network. All taxonomic groups have been considered for this analysis, taking into account established NIS in European Seas (824 taxa in total). The vast majority of the European marine NIS have their native distribution in the Western and Central Indo-Pacific, being mostly associated with introductions into the Mediterranean Sea through the Suez Canal. However, this overall pattern is heavily influenced by the fact that 76% of all NIS primary introductions in Europe have been reported first from the Mediterranean Sea. A more detailed analysis revealed various patterns of the dominating native distributions of the primarily introduced NIS in Europe, depending on the European marine subregions where they have been initially introduced and their associated pathways. There seems to be a general decrease in NIS introductions in Europe, especially when it comes to NIS with native distribution in the Temperate Northern Pacific, although this trend should be treated with caution. The information provided in the current study can be useful for tailored management of specific primary pathways per marine subregion, supporting prioritization efforts. [ABSTRACT FROM AUTHOR]

A review of the scientific literature and an analysis of unpublished material identified ~ 50 possible alien molluscs from Greece, four of which were newly reported here. Records of ~ 100 additional taxa, which would strongly inflate the alien species numbers, were excluded. Among the ~ 50 candidate species, 43 were confirmed as alien and 12 as cryptogenic. Twenty-nine alien species were considered established, and four deemed invasive. Our results are consistent with the position of Greece in the east-west Mediterranean gradient, as well as the Aegean marine environment. The contribution of well-informed citizen scientists appears to be crucial to our overall knowledge of alien molluscan biotas because only 12 alien taxa were detected during formal research projects, while 31 were first found by amateurs. No molluscan introductions were confirmed from Greece pre-1960s, and subsequent periods had variable numbers of introductions, ranging from 0 (1976–1980) to 9.5 (2006–2010). The areas with the highest alien species concentrations were the Saronikos Gulf, near the Piraeus port area, and the Dodekanisa, near the Levantine coastline. Despite a general decline in taxonomic expertise and in local knowledge, we show that these are still needed when compiling and analyzing alien species inventories that subsequently influence policy and management decisions. [ABSTRACT FROM AUTHOR]

Observations of citizen scientists have become an indispensable source in the collection of biodiversity data worldwide. In Greece, the findings of these citizen scientists, in collaboration with the Hellenic Network on Aquatic Invasive Species (ELNAIS), have resulted in compiling diverse information on marine alien species. Since 2004, the Liamis Dive Centre has recorded visual data on 12 marine alien species around Pserimos Island (Dodekanisa, Greece), thus enabling us to sequence their progression and displacement amongst other vital information. The real number of biological invasions is likely to be higher than reported here because citizen scientists do not have the scientific skills required for species identification and also due to financial constraints. Nevertheless, the high number of observers to a certain extent compensates the lack of taxonomic expertise. [ABSTRACT FROM PUBLISHER]

We herein review the Adriatic opisthobranch fauna, provide an updated checklist of 223 species and assess their distribution at regional and country levels. New Adriatic records are provided for 67 opisthobranch taxa, adding three new records for the Italian coastline, five new records for Albania, eight for Croatia and 15 for Montenegro. The presence of Hermaea bifida (Montagu, 1815), Hermaea variopicta (Costa A., 1869) and Facelina annulicornis (Chamisso & Eysenhardt, 1821) is reported for the first time from anywhere in the Adriatic Sea. Including the new findings, our inventory includes 28 species from Albania, 163 from Croatia, 178 from the Italian coastline of the Adriatic, 41 from Montenegro and 74 from Slovenia. No records were available from Bosnia and Hercegovina. Ninety species (40.4%) are widespread, and were recorded from all three main divisions (Northern, Western and Eastern Adriatic), whilst 79 species (35.4%) were reported from only one of them. At sub-division levels, the Albanian inventory is the most dissimilar to the other country/regional lists, presumably because of the lack of targeted field surveys. The highest similarity is observed amongst the Western Adriatic, Croatia and the Italian Ionian coastline. Seven alien, one possible alien and three cryptogenic opisthobranchs were reliably recorded from the Adriatic Sea. The first Mediterranean records of five species were in the Adriatic Sea, of which four species have not been found elsewhere in the Mediterranean. Shipping and aquaculture are the probable pathways for most of the alien species. A steady rate of one to two alien introductions per decade since the 1970s was evident. The Northern Adriatic coasts are the most affected by alien invasions, probably due to repeated local introductions along with shellfish transfers (oysters, mussels, Manila clams), and heavy maritime transport. [ABSTRACT FROM AUTHOR]

The European Alien Species Information Network (EASIN) aims to facilitate the exploration of alien species information in Europe, and is recognized as the information system supporting European Union Member States in the implementation of the recently published Invasive Alien Species Regulation. In this paper, we present the role and activities of the EASIN Editorial Board (EB), which is responsible for the quality assurance, safeguarding and constant improvement of EASIN. The EB is supported by a web platform that facilitates online discussions about alien species. This platform creates a virtual community by providing a forum-like interface that is moderated by the EB Members but is freely accessible to the scientific community and the general public. It allows all registered users to make comments, raise questions and share experience and expertise on alien species in Europe. Moreover, it provides a means for exchanging opinions and solving disputes in a transparent way. The overall EB activity is commonly agreed upon procedures and standards. [ABSTRACT FROM AUTHOR]

In a world where invasive alien species (IAS) are recognised as one of the major threats to biodiversity, leading scientists from five continents have come together to propose the concept of developing an international association for open knowledge and open data on IAS—termed “INVASIVESNET". This new association will facilitate greater understanding and improved management of invasive alien species (IAS) and biological invasions globally, by developing a sustainable network of networks for effective knowledge exchange. In addition to their inclusion in the CBD Strategic Plan for Biodiversity, the increasing ecological, social, cultural and economic impacts associated with IAS have driven the development of multiple legal instruments and policies. This increases the need for greater co-ordination, co-operation, and information exchange among scientists, management, the community of practice and the public. INVASIVESNET will be formed by linking new and existing networks of interested stakeholders including international and national expert working groups and initiatives, individual scientists, database managers, thematic open access journals, environmental agencies, practitioners, managers, industry, non-government organisations, citizens and educational bodies. The association will develop technical tools and cyberinfrastructure for the collection, management and dissemination of data and information on IAS; create an effective communication platform for global stakeholders; and promote coordination and collaboration through international meetings, workshops, education, training and outreach. To date, the sustainability of many strategic national and international initiatives on IAS have unfortunately been hampered by time-limited grants or funding cycles. Recognising that IAS initiatives need to be globally coordinated and ongoing, we aim to develop a sustainable knowledge sharing association to connect the outputs of IAS research and to inform the consequential management and societal challenges arising from IAS introductions. INVASIVESNET will provide a dynamic and enduring network of networks to ensure the continuity of connections among the IAS community of practice, science and management. [ABSTRACT FROM AUTHOR]

The number of alien species in the Mediterranean Sea is increasing rapidly, but few attempts have been made to evaluate impacts on specific habitat types. The present study investigated alien biodiversity in Mediterranean marine caves, both by contributing new records of Eastern Mediterranean cave aliens, and by reviewing the scattered existing literature; the main goals were to highlight potential impacts and investigate the importance of cave environments for the expansion of alien species. Seven new alien species were found in marine caves of the Aegean and Ionian seas, raising the total number of aliens reported from Mediterranean marine caves to 56 species, classified as molluscs, cnidarians, bryozoans, polychaetes, crustaceans, macroalgae, fishes and tunicates. Most cave aliens (66%) were recorded from the Southeastern Levantine coasts, specifically from Lebanese caves. Shipping and Lessepsian migration have been suggested as the main pathways of alien introduction into caves of the Mediterranean Sea. The comparison of alien cave biodiversity with the updated Mediterranean alien inventory (32 species added to the latest inventory) showed similar patterns and trends for species richness, biogeographical origin and major introduction pathways, corroborating previous findings on the high local representativeness of Mediterranean cave biodiversity. Alien species seem to have invaded mostly the entrance and semi-dark zones of shallow and/or semi-submerged caves and tunnels, whereas only a few have reached the dark inner sectors or caves of the anchialine type; thus, the unfavourable cave environment seems to be naturally protected from impacts related to opportunistic invasive species, at least to a certain point. Currently there is no research confirming any direct impacts of alien biota on the native cavernicolous one. However, some issues have emerged, implying potential threats that need to be further explored: (i) the presence of a considerable proportion of aliens in most studied marine caves of the Southeastern Mediterranean basin, (ii) the recently observed population explosion of alien cave-dwelling fishes in the same area, (iii) several indications that alien diversity in marine caves is much higher than we know today. Quantitative surveys and monitoring schemes are needed in order to evaluate potential effects of alien diversity on cave community structure and the role of marine caves as stepping stones for its expansion in the Mediterranean. [ABSTRACT FROM AUTHOR]

The Dodecanese region has a high prevalence of marine alien species due to its close proximity to the Suez Canal and associated Suez shipping lanes, as well as its location at biogeographical border between sub-tropical and tropical biota. This region is therefore very important for the early detection of alien species entering the Mediterranean Sea via the Suez Canal and it is imperative that monitoring of alien species is continued in order to assess the levels of biological invasion. We present results of marine alien surveys, carried out in April 2014 on the island of Rodos. Surveys were performed by a team of marine taxonomic experts and students as part of an EU wide training school, coordinated by the COST Action TD1209 “Alien Challenge". A variety of survey methods were employed to cover a number of coastal habitats. These included: rapid assessment surveys of epibiota on artificial structures in harbours, rapid assessment snorkelling surveys of biota on sublittoral bedrock, and quantified fishing surveys (both boat-seine and trammel net fishing methods). A total of 33 alien and cryptogenic species were recorded across all the survey techniques. Of these species, 9 represented first records for Rodos: the foraminiferan Amphisorus hemprichii, the polychaetes Branchiomma bairdi, Dorvillea similis, Hydroides dirampha and Pseudonereis anomala, the molluscs Aplysia parvula, Chama pacifica and Septifer cumingii, and the bryozoan Hippopodina feegeensis. Of note the record of the Lessepsian invader Dorvillea similis represents the second record in the Mediterranean Sea. Alien fish species represented a small but notable proportion of the diversity, biomass and number of individuals in fishing catch of both fishing methods. All alien fish species observed were already known to be present in Rodos. The addition of species firstly recorded in this study brings the total number of marine alien and cryptogenic species in the Dodecanese region up to 129 species. The vast majority of these alien species have entered unaided via the Suez Canal, but an increasing number have been introduced through hull fouling or ballast water transfer from shipping. The results highlight the value of conducting marine alien surveys with teams of a diverse range of taxonomic expertise, both in its scientific output and student training. [ABSTRACT FROM AUTHOR]

A good understanding of the mechanisms and magnitude of the impact of invasive alien species on ecosystem services and biodiversity is a prerequisite for the efficient prioritisation of actions to prevent new invasions or for developing mitigation measures. In this review, we identified alien marine species that have a high impact on ecosystem services and biodiversity in European seas, classified the mechanisms of impact, commented on the methods applied for assessing the impact and the related inferential strength, and reported on gaps in available information. Furthermore, we have proposed an updated inventory of 81 marine species in Europe, representing 13 phyla, which have a documented high impact on ecosystem services or biodiversity. Food provision was the ecosystem service that was impacted by the greatest number of alien species (in terms of both positive and negative impacts). Following food provision, the ecosystem services that were negatively affected by the highest number of alien species were ocean nourishment, recreation and tourism, and lifecycle maintenance, while the ecosystem services that were most often positively impacted were cognitive benefits, water purification, and climate regulation. In many cases, marine aliens were found to impact keystone/protected species and habitats. Thirty percent of the assessed species had an impact on entire ecosystem processes or wider ecosystem functioning, more often in a negative fashion. Forty-nine of the assessed species were reported as being ecosystem engineers, which fundamentally modify, create, or define habitats by altering their physical or chemical properties. The positive impacts of alien species are probably underestimated, as there is often a perception bias against alien species. Among the species herein assessed as high-impact species, 11 had only negative and 1 only positive impacts; for the majority (63 species), both negative and positive impacts were reported; the overall balance was often unknown. Although there is no doubt that invasive species have modified marine ecosystems, evidence for most of the reported impacts is weak, as it is based on expert judgement or dubious correlations, while only 13% of the reported impacts were inferred via manipulative or natural experiments. A need for stronger inference is evident, to improve our knowledge base of marine biological invasions and better inform environmental managers. [ABSTRACT FROM AUTHOR]

The spatial pattern of initial introductions of marine alien species in the European Seas (including the entire Mediterranean) was investigated. Marked geographic patterns depending on the pathway of introduction were revealed, with specific countries acting as gateways to alien invasions. France and Italy were the countries mostly responsible for introductions by aquaculture, while Lessepsian species were first reported (as anticipated) in the countries of the Levantine Sea, especially Israel. Shipping was the most important pathway of introduction, with a widely dispersed geographic pattern of initial introductions, especially near large ports. Certain taxonomic groups were mostly introduced by specific pathways, and hence the taxonomic identity of the introduced alien species in each region was greatly dependent on the dominant maritime activities/interventions and the related pathways of introduction. Our data can be very useful for informing and supporting national policy and management decisions necessary to prevent future introductions of marine alien species. [ABSTRACT FROM AUTHOR]

The spotted sea hare Aplysia dactylomela Rang, 1828 is a large and conspicuous opisthobranch sea slug that since 2002 has rapidly colonized the eastern Mediterranean, establishing populations in numerous localities. The source of the Mediterranean populations has been the subject of debate, with two main hypotheses considered (Atlantic and Red Sea origin). A recent study on the taxonomy of A. dactylomela has shown that the spotted sea hare is a complex of at least two genetically distinct species (A. dactylomela in the Atlantic and A. argus in the Indo-Pacific), facilitating the correct identification of Mediterranean specimens by molecular means. We used sequence data from the mitochondrial cytochrome oxidase I gene to identify the Mediterranean individuals for the first time and to infer their origin. Our results confirmed that all the specimens collected in the Mediterranean belong to A. dactylomela and therefore have an Atlantic origin. The limited sample size does not allow identification of the dispersal pathway of A. dactylomela into the Mediterranean, but the colonization sequence is consistent with a "natural" dispersal event. This hypothesis is evaluated in light of local surface circulation patterns. Possible causes for the recent and rapid invasion of the eastern Mediterranean by A. dactylomela are discussed. [ABSTRACT FROM AUTHOR]

Spatial priorities for the conservation of three key Mediterranean habitats, i.e. seagrass Posidonia oceanica meadows, coralligenous formations, and marine caves, were determined through a systematic planning approach. Available information on the distribution of these habitats across the entire Mediterranean Sea was compiled to produce basin-scale distribution maps. Conservation targets for each habitat type were set according to European Union guidelines. Surrogates were used to estimate the spatial variation of opportunity cost for commercial, non-commercial fishing, and aquaculture. Marxan conservation planning software was used to evaluate the comparative utility of two planning scenarios: (a) a whole-basin scenario, referring to selection of priority areas across the whole Mediterranean Sea, and (b) an ecoregional scenario, in which priority areas were selected within eight predefined ecoregions. Although both scenarios required approximately the same total area to be protected in order to achieve conservation targets, the opportunity cost differed between them. The whole-basin scenario yielded a lower opportunity cost, but the Alboran Sea ecoregion was not represented and priority areas were predominantly located in the Ionian, Aegean, and Adriatic Seas. In comparison, the ecoregional scenario resulted in a higher representation of ecoregions and a more even distribution of priority areas, albeit with a higher opportunity cost. We suggest that planning at the ecoregional level ensures better representativeness of the selected conservation features and adequate protection of species, functional, and genetic diversity across the basin. While there are several initiatives that identify priority areas in the Mediterranean Sea, our approach is novel as it combines three issues: (a) it is based on the distribution of habitats and not species, which was rarely the case in previous efforts, (b) it considers spatial variability of cost throughout this socioeconomically heterogeneous basin, and (c) it adopts ecoregions as the most appropriate level for large-scale planning. [ABSTRACT FROM AUTHOR]

Europe is severely affected by alien invasions, which impact biodiversity, ecosystem services, economy, and human health. A large number of national, regional, and global online databases provide information on the distribution, pathways of introduction, and impacts of alien species. The sufficiency and efficiency of the current online information systems to assist the European policy on alien species was investigated by a comparative analysis of occurrence data across 43 online databases. Large differences among databases were found which are partially explained by variations in their taxonomical, environmental, and geographical scopes but also by the variable efforts for continuous updates and by inconsistencies on the definition of 'alien' or 'invasive' species. No single database covered all European environments, countries, and taxonomic groups. In many European countries national databases do not exist, which greatly affects the quality of reported information. To be operational and useful to scientists, managers, and policy makers, online information systems need to be regularly updated through continuous monitoring on a country or regional level. We propose the creation of a network of online interoperable web services through which information in distributed resources can be accessed, aggregated and then used for reporting and further analysis at different geographical and political scales, as an efficient approach to increase the accessibility of information. Harmonization, standardization, conformity on international standards for nomenclature, and agreement on common definitions of alien and invasive species are among the necessary prerequisites. [ABSTRACT FROM AUTHOR]

The distribution of the alien crab Percnon gibbesi in the Mediterranean Sea was assessed, based on new data from four independent surveys in Albania-Montenegro, Tunisia, Libya, and Crete (Greece), personal observations of the authors and a thorough compilation of existing information. The species is reported herein for the first time from Albania, Algeria, Cyprus, Israel, and Lebanon. Percnon gibbesi rapidly increased its spatial distribution in the Mediterranean Sea after its first report in 1999. At present, twelve years after its introduction, P. gibbesi is established in most Mediterranean coasts, especially in middle latitudes. It is absent from the Adriatic Sea (except from its southern limit in the Albanian part of Otranto Strait), the Ligurian Sea, the Corsica Island, and the northern Aegean Sea, possibly because of the low winter temperatures prevailing in these areas. In the North African coasts, P. gibbesi has not yet been observed in Morocco. After its initial introduction, its further spreading in the Mediterranean basin seems to be governed primarily by natural dispersal via larval transport by currents. The invasion rate of P. gibbesi was assessed in the Kaş -- Kekova Marine Protected Area in southern Turkey, based on a time series of monitoring data from 2002 to 2010. The species was first observed in 2006 in two sites and rapidly increased its occupancy and abundance the following years. Its occupancy (probability of presence in 500 m length of coastline) reached 23% within four years from its first sighting. Its abundance increased exponentially with an intrinsic rate of increase r=0.79, corresponding to more than doubling of the population per year. [ABSTRACT FROM AUTHOR]

Percnon gibbesi is an opportunistic feeder, feeding primarily on algae, of the shallow infra-littoral rocky shores. It was first observed in 1999 in the Mediterranean Sea and has rapidly spread since then. The range expansion of the species in the Aegean and Ionian Seas was recorded and evidence of its further establishment in Greek waters was provided. Established populations were observed in areas where it had not been previously reported: the Saronikos Gulf (central Aegean Sea), Chios Island (central Aegean Sea), Milos Island (central Aegean Sea), Zakynthos Island (central Ionian Sea) and Syvota (north-eastern coast of the Ionian Sea). The species was also observed in new sites in the Messiniakos Gulf, Crete and Rhodes Island, where it had been previously reported. The species keeps spreading in the Mediterranean Sea with a high rate of expansion. [ABSTRACT FROM AUTHOR]

The finding of sixteen alien species collected around Cyprus reveals that Indo-Pacific alien species are spreading at an increasing rate in the Levantine Sea leading to homogenization of the basin. This work reports on the occurrence of six alien species previously unknown to Cyprus namely: Dendrostrea frons, Gafrarium pectinatum, Paphia textile, Septifer forskali, Spondylus spinosus, Psammotreta praerupta and many more that seem to be now well established. Purpuradusta gracilis notata an Indo-Pacific cowry, known from the Levantine basin, is currently well established along the Cypriot coast. The literature review after the CIESM Atlas and Ozturk et al. (2004) has revealed another three new alien species, namely Aplysia dactylomela, Melibe viridis and Thais lacera. Outstanding is the finding of Fulvia fragilis, an Indian Ocean species widespread throughout the Mediterranean. [ABSTRACT FROM AUTHOR]

By October 2007, a total of 31 alien marine macrophytic species had been recorded on Greek coasts. Following a critical review of these findings, these species were classified as established (9 species), casual (8 species) and debatable (14 species). There were also 23 species found in the Greek marine flora that are excluded from the list of alien macroalgae. Brief remarks are provided for the debatable species. Based on the distribution of the alien species, four are considered as invasive, although their impact on the native vegetation has not yet been documented. A trend analysis revealed that most alien species (65% of current total) were found in the period 1971–2007. Shipping contributes to most alien macroalgal immigration (48%), followed by progressive immigration via the Suez Canal (33%), while aquaculture plays a minor role (16%), unlike the western Mediterranean Sea where aquaculture accounts for 73% of the macrophyte introductions. [ABSTRACT FROM AUTHOR]

Species of marine bivalve molluscs identified in the last nine years in the Greek waters have been used to update the checklist published in 1996 (Fauna Graeciae VII) by inserting necessary changes and adding new records. The updated version includes 13 new species among which three are exotics (non-Mediterranean species), five rare, two new deep sea and one previously considered a fossil species. Also, as a result of new resources, the distributions of pre-existing native molluscs have been updated to include new habitat areas. The nomenclature is also up to date based on the CLEMAM Database. Thus five species are now excluded either because they are junior synonyms of pre-existing valid species (2) or because of old spurious records (3 species). Additions and corrections of the 1996 checklist have resulted in a total of 308 bivalves in Greek waters. [ABSTRACT FROM PUBLISHER]

In the present work, we analysed time series data on the introduction of new non-indigenous species (NIS) in the Mediterranean between 1970 and 2017, aiming to arrive at recommendations concerning the reference period and provisional threshold values for the NIS trend indicator. We employed regression analysis and breakpoint structural analysis. Our results confirm earlier findings that the reference conditions differ for the four Mediterranean subregions, and support a shortening of the reporting cycle from six to three years, with a two-year time lag for the ensuing assessment. Excluding Lessepsian fishes and parasites, the reference period, defined as the most recent time segment with stable mean new NIS values, was estimated as 1997–2017 for the eastern Mediterranean, 2012–2017 for the central Mediterranean, 2000–2017 for the Adriatic and 1970–2017 for the western Mediterranean. These findings are interpreted primarily on the basis of a basin scale temperature regime shift in the late 1990s, shifts in driving forces such as shellfish culture, and as a result of intensified research efforts and citizen scientist initiatives targeting NIS in the last decade. The threshold values, i.e., the three-year average new NIS values during the reference period, are indicative and will ultimately depend on the choice of species and pathways to be used in the calculations. This is discussed through the prism of target setting in alignment with specific management objectives. [ABSTRACT FROM AUTHOR]

The diversity and distribution of the Bivalvia fauna is examined in the various seas of Greek territorial waters. There is a statistically significant correlation between the bibliographical sources and the recorded variety of Bivalvia at any given area, with the deeper areas containing fewer species. Attention is given to some species ‘introduced’ into the area.Cluster analysis, based on the species present at 30 regions which represent distinct geographical and ecological units, do not show any differentiation that corresponds to a geographical pattern. However, a distinct group is associated with the deeper open areas, which suggests that ecological parameters, such as depth and degree of enclosure, play an important role in the distribution of species. [ABSTRACT FROM PUBLISHER]

Based on the bivalve fauna known from an extensively studied zone, along the infralittoral in the Patras Gulf, a biotope approach was attempted using numerical taxonomy methods. The efficiency of various combinations of similarity measures and clustering techniques is discussed for this type of data (single group – binary). Four main station groups were delimited which were further assigned to the biotopes of known Mediterranean biocoenoses. The four groups correspond to: (a) the biotope of the Posidonia beds (HP) and that of coarse sands and fine gravels under the influence of bottom currents (SGCF). The limits of these two biocoenoses are not clear-cut, (b) The biotope of the coastal detritic bottoms (DC) usually occurring in deeper areas but met in the infralittoral under environmental stress, (c) A transitional zone where degenerating Posidonia meadows are gradually replaced by Cymodocea and Zostera, facies of the muddy sand in sheltered areas biocoenoses (SVMC). This degradation can be attributed to various disturbing factors including natural environmental changes, (d) The biotope of fine well-sorted sands (SFBC). A typical malacofauna is present with the addition of some species. Regardless of the differences, Pérès & Picard's (1964) scheme is more appropriate in the Mediterranean ecosystems than any other northern European scheme. [ABSTRACT FROM PUBLISHER]

Focuses on the survey of benthic fauna in the regions of Aegean Sea. Study on the habitat of benthic fauna; Examination on the baseline of benthic species; Purpose of the survey.

. The changes in the concentrations of silicate, phosphate, and inorganic nitrogen in Eiefsis Bay. an intermittently anoxic basin, arc described and related to the changes in the physical properties of the water. Winter convection resulted in a very small vertical gradient of temperature, salinity, oxygen, and nutrients. Stratification started to develop in May and persisted for about 6 months. High values of silicate, phosphate, and ammonia occurred during the anoxic conditions prevailing in summer. The vertical transport of particulate organic matter and decomposition of abundant pelagic and benthic organic matter during the summer produced a low oxygen level in the bottom layer below the pycnoclinc. A high sea water temperature and vertical stability contributed to the development of anoxic conditions during the summer in the near bottom layer and to mass mortality of benthic macrofauna. Also the Eiefsis Bay anoxia appears to have had significant ecological effects on many other marine species, including several of economic importance. [ABSTRACT FROM AUTHOR]

The number of marine alien species reported in Galil (Biol Invasions, 2009) is incomplete. Recent literature suggests that the number of aliens is nearly 1,000 and that the introduction rate is way off the 10 species per year suggested by Galil (Biol Invasions, 2009). [ABSTRACT FROM AUTHOR]

The current amendments to the Mediterranean marine Non-Indigenous Species (NIS) inventory for the period 2017-2019 are the result of a continuous literature search and update of the Hellenic Centre for Marine Research (HCMR) offline database. They take into account recent findings, previously missed records, back-dated records based on the re-examination of existing material or phylogenetic studies and changes in nomenclature. During the period 2017-2019, 70 new species were added to the inventory of established species, 25 that had escaped our attention in the past and 23 newly introduced, which have already established self-sustaining populations. Meanwhile, 22 species previously known only with casual records have established viable populations and a total of 36 species have expanded their distribution into new Marine Strategy Framework Directive regions, primarily the Central Mediterranean and the Adriatic Sea. Intensified research efforts, prompted by the reporting obligations created by recent legislation, complemented by ever expanding networks and initiatives involving citizen scientists have certainly contributed to higher rates of discovery of alien species presences. However, the expansion of tropical and sub-tropical species into the cooler waters of the Aegean, the Adriatic and the western Mediterranean indicates that the warming of Mediterranean waters due to climate change is also facilitating the geographic expansion of NIS in the region. The rate of new introductions in this 3-year period is 8 species per year for the whole Mediterranean, without taking into account casual records or species with reporting lags. Only 4 species per year enter through the Suez Canal, while a considerable number of species are introduced through shipping vectors and the aquarium trade. Acknowledging the dynamic nature of invasions and the uncertainty inherent in compiling check lists, we consider the present work as the most accurate and up-to-date NIS list to inform policy, management and decision-making. [ABSTRACT FROM AUTHOR]

Using long-term data of 149 warm alien species since 1924, we show that the introduction of warm and tropical alien species has been exacerbated by the observed warming of the eastern Mediterranean Sea. The phenomenon has accelerated after an abrupt shift in both regional and global temperatures that we detect around 1998, leading to a 150% increase in the annual mean rate of species entry after this date. Abrupt rising temperature since the end of the 1990s has modified the potential thermal habitat available for warm-water species, facilitating their settlement at an unexpectedly rapid rate. The speed of alien species spreading and response to global warming is apparently much faster than temperature increase itself, presenting an important warning for the future of Mediterranean Sea biodiversity. In addition to the sea warming, other factors that enable and enhance biological invasions, such as salinity increase and oceanographic forcing, are also discussed. [ABSTRACT FROM AUTHOR]

The finding of sixteen alien species collected around Cyprus reveals that Indo-Pacific alien species are spreading at an increasing rate in the Levantine Sea leading to homogenization of the basin. This work reports on the occurrence of six alien species previously unknown to Cyprus namely: Dendrostrea frons, Gafrarium pectinatum, Paphia textile, Septifer forskali, Spondylus spinosus, Psammotreta praerupta and many more that seem to be now well established. Purpuradusta gracilis notata an Indo-Pacific cowry, known from the Levantine basin, is currently well established along the Cypriot coast. The literature review after the CIESM Atlas and Ozturk et al. (2004) has revealed another three new alien species, namely Aplysia dactylomela, Melibe viridis and Thais lacera. Outstanding is the finding of Fulvia fragilis, an Indian Ocean species widespread throughout the Mediterranean. [ABSTRACT FROM PUBLISHER]