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This study presents the first comprehensive assessment of alien species occurrences within the selected 11 Marine Protected Areas (MPAs) located on the Aegean and Levantine coasts of Turkey. The inventory includes a total of 289 species belonging to 15 phyla, in which lowest and highest diversities were observed in Saros Bay MPA (27 species, northern Aegean Sea) and Fethiye-Gocek Bay MPA (150 species, northwest Levantine Sea), respectively. Alien species distributions that were revealed in protected areas located in the southern Aegean and Levantine Seas were 56.9% similar (based on presence vs. absence data), while northern Aegean sites formed another distinct group. According to the breakdown of major phyla through the entire study areas, Mollusca had the highest alien diversity (22.1% of alien species), followed by Actinopterygii (19.0%), Arthropoda (15.2%) and Annelida (13.5%). Casual aliens were represented by very low proportions in each MPA, proving that most species were already established in the region, with a significant proportion of invasive species. Regardless of the localities, the majority of the species originated from the Red Sea, whose primary pathway of introduction is the corridor, the Suez Canal. In the absence of effective management actions against bioinvasions, MPAs located along the Turkish coastline do not currently seem to provide any protection, revealing a large conservation gap to be filled.

The coralligenous habitat was studied at the large Mediterranean scale, by applying a standardized, non-destructive photo-sampling protocol, developed in the framework of the CIGESMED project. The results provided evidence to support the following statements: (a) the assemblage pattern is not homogeneously distributed across the four Mediterranean ecoregions studied (biotic gradients hypothesis); and (b) the assemblage pattern does not change significantly when the information is aggregated to higher taxonomic levels (taxonomic sufficiency hypothesis). Surrogate taxonomic categories higher than species, such as genus and family, can be used to reveal the multivariate pattern of the coralligenous assemblages. Although preliminary at the pan-Mediterranean scale, these outcomes set the scene for future comparisons as more data sets become available but also for comparisons between taxonomic and functional patterns. 1.2.3.4.

WOS: 000345597500001, 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 87 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, 17 had only negative and 7 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., European UnionEuropean Union (EU) [308392, 287600]; European UnionEuropean Union (EU) [308392, 287600], SK and ACC were partly supported by the DEVOTES (DEVelopment Of innovative Tools for understanding marine biodiversity and assessing good Environmental Status) project, which was funded by the European Union under the 7th Framework Programme, `The Ocean for Tomorrow' Theme (grant agreement no. 308392), www.devotes-project.eu. AZ was supported by the PERSEUS (Policy-oriented marine Environmental Research for the Southern EUropean Seas) project, which was funded by the European Union under the 7th Framework Programme (grant agreement no. 287600). We thank C. Liquete, M. Thomsen, M. Hanson, and two anonymous reviewers for their useful comments, and G. Mulhern for linguistic editing.