10.25607/t2smha d19b9fd8-f411-40aa-966a-481fc8cd0453 http://ipt.medobis.eu/resource?r=greekmarineicas_geodataset Maria Sini Department of Marine Sciences, University of the Aegean Research Assistant

GREECE

0000-0002-9608-3503 Michail Ragkousis Department of Marine Sciences, University of the Aegean PhD Student

GREECE

0000-0002-3886-4280 Stelios Katsanevakis Department of Marine Sciences, University of the Aegean Professor

GREECE

stelios@katsanevakis.com 0000-0002-5137-7540 Argyro Zenetos Institute of Marine Biological Resources and Inland Waters, Hellenic Centre for Marine Research Research Director

GREECE

zenetos@hcmr.gr 0000-0003-2670-042X Nikoletta Koukourouvli Cartographer

GREECE

0000-0002-3697-9850 Maria Sini Department of Marine Sciences, University of the Aegean Research Assistant

GREECE

mariasini@marine.aegean.gr 0000-0002-9608-3503 Ioannis Rallis Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Centre for Marine Research Marine Biologist, PhD candidate

Heraklion

i.rallis@hcmr.gr 0000-0002-1384-9906 CUSTODIAN_STEWARD Dimitra Mavraki Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Centre for Marine Research Data Manager 0000-0001-6775-530X CUSTODIAN_STEWARD 2025-09-26 ENGLISH The GreekMarineICAS geodataset was created as part of the project ALAS: Aliens in the Aegean – A Sea Under Siege project (https://alas.edu.gr/), with the aim to assess the spatial extent and potential impacts of alien species in the Aegean Sea, and to improve our understanding of the mechanisms driving the impacts of invasive alien species on native marine ecosystems. Methodology of data compilation: Initially, an ICAS catalogue was created, including species classified as of high impact in the European Alien Species Information Network (EASIN), or as invasive or of high impact in recent review papers. A thorough search was conducted to look for information on the presence of these species in the Greek Seas. Georeferenced data, along with information on the reported date / year of sighting, depth range, abundance and habitat type were compiled using all available types of data sources, including published scientific literature, grey literature (e.g., theses, technical reports, and newspaper reports), offline databases (including records from past projects of universities, research institutes, the ELNAIS database, and citizen science initiatives), online scientific or citizen science databases (Algaebase, GBIF, OBIS, iNaturalist - only research-grade data), social networks (e.g., Instagram and Facebook), as well as through field work involving scientific diving and interviews with marine scientists, fishers and divers that were carried out during the ALAS project. In situ underwater sampling during the ALAS project was carried out in 2020 at 156 sites, and all sampling was conducted using non-destructive visual sampling techniques via SCUBA or free diving, down to a maximum of 20 m depth. Moreover, an unstructured interview approach was applied during the respective interviews with marine scientists, fishers and divers, while a photographic guide of the targeted ICAS was produced and provided during the interviews to enhance the species verification process. Information from social networks was specifically retrieved from the websites of diving centers, which were thoroughly checked for images of ICAS, and once relevant images were found the corresponding information was further validated through direct communication. All data were organized within an Excel spreadsheet and all duplicate records were deleted. Occurrence GBIF Dataset Type Vocabulary: http://rs.gbif.org/vocabulary/gbif/dataset_type_2015-07-10.xml biological invasions none non-indigenous species none Mediterranean Sea Marine Regions introduced and exotic species none Observation GBIF Dataset Subtype Vocabulary: http://rs.gbif.org/vocabulary/gbif/dataset_subtype.xml This work is licensed under a Creative Commons Attribution Non Commercial (CC-BY-NC) 4.0 License . Creative Commons Attribution Non Commercial 4.0 International https://spdx.org/licenses/CC-BY-NC-4.0.html CC-BY-NC-4.0 http://ipt.medobis.eu/archive.do?r=greekmarineicas_geodataset The GreekMarineICAS geodataset covers all coastal waters of the Aegean, Levantine, Ionian, and Adriatic Seas that are included within the Greek reporting obligations under the Marine Reporting Units of the Marine Strategy Framework Directive of the European Union Seas (collectively referred to as the Greek Seas). 19.116 30.146 41.443 34.38 1893-01-01 2020-12-31 60 marine ICAS (56 alien and 4 cryptogenic) belonging to 14 phyla, namely Chordata-Teleostei (16 species), Mollusca (14), Arthropoda (seven), Rhodophyta (four), Chlorophyta (three), Chordata – Tunicata (three), Annelida (two), Bryozoa (two), Echinodermata (two), Cnidaria-Anthozoa (one), Cnidaria – Scyphozoa (one), Ctenofora (one), Foraminifera (one), Ochrophyta (one), Porifera (one), Tracheophyta (one). Class Teleostei Phylum Mollusca Phylum Arthropoda Phylum Rhodophyta Phylum Chlorophyta Subphylum Tunicata Phylum Annelida Phylum Bryozoa Phylum Echinodermata Subphylum Anthozoa Class Scyphozoa Phylum Ctenophora Phylum Foraminifera Phylum Ochrophyta Phylum Porifera Phylum Tracheophyta unkown Maria Sini Department of Marine Sciences, University of the Aegean Research Assistant

GREECE

mariasini@marine.aegean.gr 0000-0002-9608-3503 All data were organized within an Excel spreadsheet and all duplicate records were deleted. Greek Seas Methodology of data compilation: Initially, an ICAS catalogue was created, including species classified as of high impact in the European Alien Species Information Network (EASIN), or as invasive or of high impact in recent review papers. A thorough search was conducted to look for information on the presence of these species in the Greek Seas. Georeferenced data, along with information on the reported date / year of sighting, depth range, abundance and habitat type were compiled using all available types of data sources, including published scientific literature, grey literature (e.g., theses, technical reports, and newspaper reports), offline databases (including records from past projects of universities, research institutes, the ELNAIS database, and citizen science initiatives), online scientific or citizen science databases (Algaebase, GBIF, OBIS, iNaturalist - only research-grade data), social networks (e.g., Instagram and Facebook), as well as through field work involving scientific diving and interviews with marine scientists, fishers and divers that were carried out during the ALAS project. In situ underwater sampling during the ALAS project was carried out in 2020 at 156 sites, and all sampling was conducted using non-destructive visual sampling techniques via SCUBA or free diving, down to a maximum of 20 m depth. Moreover, an unstructured interview approach was applied during the respective interviews with marine scientists, fishers and divers, while a photographic guide of the targeted ICAS was produced and provided during the interviews to enhance the species verification process. Information from social networks was specifically retrieved from the websites of diving centers, which were thoroughly checked for images of ICAS, and once relevant images were found the corresponding information was further validated through direct communication. For taxonomy, the WoRMS has been used and for localities the Marine Region Gazetteer The GreekMarineICAS geodataset was created as part of the project ALAS: Aliens in the Aegean – A Sea Under Siege project (https://alas.edu.gr/), with the aim to assess the spatial extent and potential impacts of alien species in the Aegean Sea, and to improve our understanding of the mechanisms driving the impacts of invasive alien species on native marine ecosystems. Greek Seas 2026-04-14T08:23:49Z Sini M, Ragkousis M, Katsanevakis S, Zenetos A, Koukourouvli N (2025). Marine impactful cryptogenic and alien species in the Greek Seas: A georeferenced dataset (1893-2020). Version 2.4. Hellenic Center for Marine Research. Occurrence dataset https://doi.org/10.25607/t2smha accessed via GBIF.org on 2026-04-14. Ragkousis M., Sini M., Koukourouvli N., Zenetos A., Katsanevakis S. (2023). Invading the Greek Seas: spatiotemporal patterns of marine impactful alien and cryptogenic species. Diversity 15, 353. doi: 10.3390/d15030353 Tsirintanis K., Sini M., Ragkousis M., Zenetos A., Katsanevakis S. (2023). Cumulative negative impacts of invasive alien species on marine ecosystems of the Aegean Sea. Biology 12(7), 933. doi: 10.3390/biology12070933