Is the trend in new introductions of marine non-indigenous species a reliable criterion for assessing good environmental status? Τhe case study of Greece

Abstract

This study presents the updated status of marine non-indigenous species (NIS) distribution in Greece and investigates trends in new NIS introductions, at both national and subnational level, during 1970-2017. The overall picture shows an increase in new introductions from the 1970s to 2017. The number of unaided introduced species (mainly Lessepsian immigrants) followed an upward trend in the South Aegean Sea until 2017. Similarly, the number of NIS associated with transport-stowaway (NIS introduced mainly via ballast and boat hulls) followed an upward until 2017 in the South Aegean Sea, but also in the Hellenic Levantine coasts. However, these results are greatly affected by a monitoring bias, which appears to be the main factor influencing the number of new NIS introductions reported from Greece and its subnational areas. This monitoring bias, as well as the continuous influx of Lessepsian NIS into the Aegean Sea, constitutes a challenge for Greece as regards setting exact boundaries for areas with or without Good Environmental Status (GES), based on Descriptor 2, primary criterion C1 (D2C1), of the Marine Strategy Framework Directive (MSFD). Dedicated monitoring of marine NIS should be established and be constant in space, time and across taxonomic groups. Prioritization should be given to hot-spot areas of new NIS introductions, such as ports, aquaculture units and marine protected areas. This should be a prerequisite for applying the primary criterion D2C1 of the MSFD properly, at both national and subnational level. Finally, as regards the implementation of D2C1 of the MSDF and setting exact threshold values, we highlight the need for subregional and regional coordination in the Mediterranean.

Spatio‐temporal dynamics of exotic fish species in the Mediterranean Sea: Over a century of invasion reconstructed

“…Introduction trends provide simple but essential information (Seebens et al, 2021 ) for national (Zenetos et al, 2020 ) and regional (Galil, 2009 ) inventories, notably because the number of introduced species, combined with the available published sightings allows exploring the process in its evolution and observation.…”

MSFD In-Depth Knowledge of the Marine Environment as the Stepping Stone to Perform Marine Spatial Planning in Greece

“…In addition, indigenous flora and fauna are threatened by NIS entering in other ways apart from the introductions via the Suez Canal. The most important vectors of introduction are imports for aquaculture purposes and trade; fouling on merchant ships and/or yachts; in ballast water; and escapes/releases from aquariums [60,61].…”

“…A total of 242 marine NIS have been recorded in Greek waters as of 2020. The taxonomic group with the highest number of NIS are fishes, contributing with 51 species, followed by 50 molluscs, 43 crustaceans, and 33 annelids [61].…”

“…Freshwater biota occurs mostly in northern Greece. For all source regions and taxonomic groups considered, the invasion rate has been increasing since the end of the last century; this trend is indirectly related to the "tropicalization" of the Mediterranean Sea [60,61].…”

Two-way bioinvasion: tracking the neritic non-native cyclopoid copepods Dioithona oculata and Oithona davisae (Oithonidae) in the Eastern Mediterranean Sea

“…Most non-native copepods in the Mediterranean Sea coastal waters are of Indo-Pacific origin, and were first introduced into the Levantine Basin via the Suez Canal and by ballast water from shipping and hull fouling (Katsanevakis et al, 2014;Armon & Zenetos, 2015;Sabia et al, 2015). To date, 61 non-native copepods have been recorded in the Mediterranean Sea, of which 12 are cyclopoid copepods (based on a compilation of Abdel-Rahman, 2005;Zenetos et al, 2010Zenetos et al, , 2012Zenetos et al, , 2020Zakaria, 2015).…”