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Status and Trends in the Rate of Introduction of Marine Non-Indigenous Species in European Seas

by 1,*, 2, 3, 4, 5,6, 7,8, 9, 10,11, 12, 13, 14, 14, 15,16, 17, 16,18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 17, 27, 25, 12, 12, 10,11, 10, 28, 19, 29 and 22add Show full author list remove Hide full author list
Hellenic Centre for Marine Research (HCMR), 16604 Anavyssos, Greece
Karaiskaki 16 Voula, 16673 Athens, Greece
ÜEE LLC, Marine Ecology Division, Teknopark Izmir A1/49, 35437 Urla, Turkey
EEA-European Environment Agency, Kongens Nytorv 6, 1050 Copenhagen, Denmark
IPMA, I.P.-Portuguese Institute for the Sea and Atmosphere, Rua Alfredo Magalhães Ramalho nº 6, 1495-006 Algés, Portugal
MARE-Marine and Environmental Sciences Centre, Departamento de Ciências e Engenharia do Ambiente, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
MARE-Marine and Environmental Sciences Centre/ARNET—Aquatic Research Network, Regional Agency for the Development of Research, Technology and Innovation (ARDITI), Madeira Island, 9020-105 Funchal, Portugal
Smithsonian Environmental Research Center, 647 Contees Wharf Road, Edgewater, MD 21037, USA
Italian Institute for Environmental Protection and Research (ISPRA), Department for the Monitoring and Protection of the Environment and for the Conservation of Biodiversity, Lungomare C. Colombo 4521–Addaura, 90149 Palermo, Italy
MARE, Marine and Environmental Sciences Center, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
CINEA and ESTS, IPS–Energy and Environment Research Center, Instituto Politécnico de Setúbal, Estefanilha, 2910-761 Setúbal, Portugal
Instituto Español de Oceanografía (IEO, CSIC), Centro Oceanográfico de Baleares, Muelle de Poniente s/n, 07015 Palma de Mallorca, Spain
Faculdade de Ciências e Tecnologias and BIOPOLIS Program in Genomics, InBIO/CIBIO-Research Center in Biodiversity and Genetic Resources, Universidade dos Açores, R. Mãe de Deus 13A, 9500-321 Ponta Delgada, Portugal
Institute of Oceanography and Fisheries, Šetalište Ivana Meštrovića 63, 21000 Split, Croatia
Eurofins AquaSense, Korringaweg 7, 4401NT Yerseke, The Netherlands
Naturalis Biodiversity Center, Darwiweg 2, 2333CR Leiden, The Netherlands
Department of Aquatic Resources, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden
GiMaRIS, Rijksstraatweg 75, 2171AK Sassenheim, The Netherlands
Department of Ecoscience, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark
Institute of Marine Research, Nye Flødevigveien 20, 4817 His, Norway
Royal Belgian Institute of Natural Sciences (RBINS), 8400 Oostende, Belgium
Marine Research Centre, Finnish Environment Institute, Latokartanonkaari 11, 00790 Helsinki, Finland
Italian Institute for Environmental Protection and Research (ISPRA), Department for the Monitoring and Protection of the Environment and for the Conservation of Biodiversity, Via Brancati 60, 00144 Rome, Italy
Marine & Aquatic Environment, Ministry of Environment, Environmental Protection Agency, Tolderlundsvej 5, 5000 Odense, Denmark
Institute of Marine Biology, University of Montenegro, Put I Bokeljske Brigade 68, 85330 Kotor, Montenegro
Centre D’expertise et de Données Patrimoine Naturel, OFB, CNRS, MNHN, 75005 Paris, France
Marine Biology Station Piran, National Institute of Biology, Fornače 41, SI–6330 Piran, Slovenia
Office for Risk Assessment and Research, Netherlands Food and Customer Product Safety Authority, Ministry of Economical Affairs, 3540AA Utrecht, The Netherlands
Institute of Evolutionary Sciences of Montpellier (ISE-M, UMR 5554), University of Montpellier, CNRS, Bâtiment 24, 34095 Montpellier, France
Author to whom correspondence should be addressed.
Diversity 2022, 14(12), 1077;
Received: 1 November 2022 / Revised: 27 November 2022 / Accepted: 28 November 2022 / Published: 6 December 2022


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.

1. Introduction

The introduction of marine Non-Indigenous Species (NIS) is widely perceived as one of the main threats to biological diversity next to habitat destruction at a global scale [1,2]. Invasive Alien Species (IAS) are a subset of NIS, which are of particular concern due to their ability to naturally reproduce in the recipient areas, spread rapidly, and threaten biological diversity in various ways, from reducing genetic variation and modifying gene pools, displacing, hybridizing or competing with local endemic or native species to altering habitat and ecosystem functioning [3,4,5,6,7]. It is essential to note that the term “invasive” may have various implications depending on the context. From a scientific perspective, “invasive” refers to the ability of the species to survive, reproduce and spread in the invaded region [8], whereas political frameworks, such as the EU Regulation (No 1143/2014) on the prevention and management of the introduction and spread of invasive alien species (IAS Regulation) often connect invasiveness to impact.
Marine NIS, and IAS in particular, are addressed by European Union (EU) policies, such as the EU Biodiversity Strategy 2020 (COM (2011) 244) target 5; the European Water Framework Directive (WFD) (2000/60/EC); the EU Marine Strategy Framework Directive (MSFD) (2008/56/EC) with a dedicated descriptor (D2 “Non-indigenous species introduced by human activities are at levels that do not adversely alter the ecosystems”) and the IAS Regulation (No 1143/2014). Non-indigenous species is one of the 11 descriptors in the MSFD that refer to anthropogenic pressures on the marine environment of the EU [9]. In the latest MSFD update [9] among the criteria for assessing descriptor D2 on marine NIS, primary criterion D2C1 concerning new NIS introductions states that: “The number of non-indigenous species which are newly introduced via human activity into the wild, per assessment period (6 years), measured from the reference year (2011) as reported for initial assessment under Article 8(1) of Directive 2008/56/EC, is minimised and where possible reduced to zero”. Efforts to make this target more quantitative are ongoing [10,11,12], further encouraged by Target 6 of the first draft of the Convention on Biological Diversity (CBD) Post-2020 Global Biodiversity Framework, which stipulates at least a 50% reduction in the rate of new introductions [13]. However, to date, only the Baltic Marine Environment Protection Commission (Helsinki Convention, HELCOM) has set a numerical threshold of zero new NIS introductions through anthropogenic activities in the Baltic Sea [10]. At the EU level, Tsiamis et al. [14] suggested that the most suitable approach for setting the Good Environmental Status (GES) thresholds for criterion D2C1 would be a percentage reduction of new NIS introductions for an assessment period compared to the previous six-year assessment period (baseline). Preferably, the more previous six-year cycles that are included in the assessment, the better (e.g., starting from the 1970s) since the inclusion of earlier assessment periods enables tracking down how management measures have changed the result of the assessment over time. Thus, as qualitative GES descriptions turn into quantitative targets, it is now more imperative than ever that information on NIS in European seas is as accurate and complete as possible to provide a sound baseline for future management.
The first compilation of marine NIS inventory in Europe was conducted by Streftaris et al. [15] and followed by an update in 2009 toward the SEBI2010 report [16]. In the same period, comprehensive data collection from a wide range of taxonomic groups through the EU-funded project Delivering Alien Species Inventories for Europe resulted in a European database [17]. The DAISIE database, which included recorded information on the impacts, pathways of introduction, and associated references, was integrated into the information system on Aquatic Non-Indigenous and Cryptogenic Species (AquaNIS) [18]. In parallel, the European Alien Species Information Network (EASIN) [19] has been developed by the European Commission’s Joint Research Centre (JRC) aiming to facilitate the exploration of existing alien species information from a variety of distributed information sources through freely available tools and interoperable web services, compliant with internationally recognized standards. Updated information on NIS is provided by data partners and the editorial board of EASIN [20]. AquaNIS stores and disseminates information on NIS introduction histories, recipient regions, taxonomy, biological traits, impacts, and other relevant documented data. The system is continuously updated with new NIS records provided by registered data providers.
With the digital infrastructure in place and prompted by the increased demands placed by legislation, there is an increasing availability of national (e.g., Portugal) [21] and regional inventories of NIS (e.g., Baltic [22], Mediterranean [23], Black Sea [24]), which have been instrumental for analyzing trends and pathways of NIS introductions at national (e.g., Italy [25], Greece [26], Denmark [27], Belgium [28]), subregional (Macaronesia [29]), regional (Mediterranean [30], Baltic [22]), and global scales [31]. All these assessments have the shared ambition to assess the most updated status of NIS and provide a robust baseline for understanding trends in new NIS arrivals and pathways. Such knowledge is essential for the optimal implementation of existing policies and for evaluating policy effectiveness. Furthermore, knowledge is important to evaluate the need for new policies and management strategies. Updated and validated NIS inventories constitute a milestone for the implementation of the MSFD D2. Based on refined baseline inventories of NIS set by each EU Member State (MS), in the context of the MSFD and the updated data of EASIN, Tsiamis et al. [32] estimated that 787 non-indigenous taxa were found in EU marine and partially transitional waters (including Macaronesia) by the end of 2011. Further, Tsiamis et al. [14] updated the EASIN marine data at the national and MSFD subregional levels up to 31 December 2017. In the period of 2018–2020, not only have new NIS been identified in the European seas, but also new information has emerged on the taxonomic identity (e.g., as a consequence of recent taxonomic revision efforts), biogeographic origin, and distribution of NIS records, resulting in significant changes in both the status and distribution of several species. Now more than ever, it is crucial to reassess, revise and update the NIS inventories at all spatial assessment levels. In this context, the present work presents the most updated list of marine NIS introduced in the EU and surrounding waters validated by national experts and examines trends in these NIS introductions at European, regional, and subregional levels paving the way for the setting of threshold values for new NIS introductions in the context of the MSFD, and particularly of the primary criterion D2C1.

2. Methodology

The national inventories of EU countries submitted to JRC for the purposes of the 2012–2017 assessment cycle [33] formed the starting point for the revision process. They were updated with published data from biodiversity and hot-spot campaigns, academic surveys, and citizen science project observations until December 2020 (reported until June 2022). For Norway, Albania, and Montenegro, local experts were invited. The subsequent validation of the revised lists with the contribution of national experts included several rounds of communication whereby many discrepancies were resolved, and several controversial species were agreed upon. Subsequently, the national data were aggregated at subregional, regional, and Pan-European levels. The species list includes every first novel report of species introduction, irrespective of the establishment status. In our analysis, we only considered the first new record of a NIS within a region/subregion. Duplicate records for any given species were removed to avoid overestimating new NIS records at all spatial levels. The number of species detected/observed per six-year cycles since 1970 was analyzed from these datasets.

2.1. Geographic Coverage

The study area included European marine waters surrounding EU countries, EU candidate countries (Albania, Montenegro), and Norway a country of the European Economic Area (EEA) all divided into regions and subregions (Figure 1, Table 1) as per the MSFD delineation [33]. Marine waters of the United Kingdom (UK), Turkey, and Russian Federation were not considered in this work, meaning that NIS records from these countries are not included.
The Baltic Sea (BAL) is here regarded as both a region and a subregion according to the MSFD delineation, and the same applies to the Black Sea (BLK). The North-East Atlantic (NEA) comprises four MSFD subregions, namely: (a) Greater North Sea (ANS) (b) Celtic Seas (ACS), (c) the Bay of Biscay and the Iberian Coast (ABI), and (d) Macaronesia (AMA). The ANS spans the Kattegat, the eastern English Channel, and a small part of the Western English Channel. It covers NIS in coastal and estuarine waters from seven countries including Norway (an EEA country). The Celtic Seas (ACS) are represented only by Ireland and the western English Channel waters of France. Macaronesia (AMA) is a complex of oceanic islands located in the NEA. The region comprises the archipelagos of the Azores (Portugal), Madeira (Portugal), Canary Islands (Spain), and Cabo Verde. For the present paper exclusively European Macaronesia (i.e., the Azores, Madeira, and Canary Islands), which.h is the European marine ecoregion within the Lusitanian province following the proposed classification in [35], was considered. The Mediterranean Sea (MED) includes four MSFD subregions: (a) the Western Mediterranean Sea (MWE); (b) the Ionian Sea and the Central Mediterranean Sea (MIC); (c) the Adriatic Sea (MAD); and (d) the Eastern Mediterranean Sea (MAL), encompassing the Aegean and Levantine basins.

2.2. Data Included

The most recent MSFD D2 evaluation recommendations [13] were largely followed for the inclusion of marine NIS in the present analyses. Accordingly, cryptogenic, and crypto-expanding species for the regions considered were removed from NIS lists and subsequent analyses. The terms cryptogenic and crypto expanding refer to uncertainties in the status of a species in relation to either their true native range [36] or true dispersion pathway (i.e., natural range expansion vs. human-mediated expansion) [14].
Species with insufficient information or new records unverified by experts or NIS with unresolved taxonomic status [32] were included in this study only after detailed scrutiny by different experts and a general agreement that there is a strong indication that their presence and distribution pattern implies an introduction event. It is worth mentioning the case of the annelid Laonome xeprovala, by Bick and Bastrop in Bick et al., 2018, a species described from the Netherlands and subsequently found in other Dutch rivers, canals, and estuaries [37], as well as in the eastern part of the Baltic Sea, and identified originally as Laonome calida Capa, 2007 [38]. Previous literature suggests that North America’s eastern coast is a potential native origin for Laonome xeprovala, although further clarification is still required [39].
It has been heavily debated in recent years whether parasitic NIS and pathogens (including disease agents) should be omitted from MSFD D2 since they are managed under the Aquatic Animal Health Directive (2006/88/EC) [32]. Overall, the JRC group agreed that these NIS should be reported in D2 criteria, but not considered when assessing against a GES threshold [14]. Aiming to produce results that are as representative and comparable as possible with future GES assessments, parasites and pathogens are listed in Table 2 but were not considered in the D2 trend and status analyses.
There are contrasting opinions among national NIS experts with regard to microscopic algae (phytoplankton) and to their native, cryptogenic, or NIS status, which is reflected in the literature [40] but also in the information systems of EASIN and AquaNIS. However, due to the high reproductive potential of phytoplankton and thus the high potential of spreading, it is important to have a gauge on phytoplankton expansion. The JRC invited the D2 NIS experts’ network to contact phytoplankton experts across Europe, to set up a working group that could deliver a consolidated revision of phytoplankton NIS in European seas [14]. Given that further clarification is yet to be provided regarding the status of microalgae in Europe, they are listed in Table 2 but were not considered in the D2 trend and status analyses.
Oligohaline species are included if such species were found in estuarine or coastal systems of the marine region.
NIS spreading from one region/subregion to another through natural dispersal mechanisms (secondary introduction) is included in our analyses. Their introduction pathway was classified as UNAIDED. Such is the case of many Red Sea species that have invaded the eastern Mediterranean (known as Lessepsian immigrants) and are progressively moving to the central and western Mediterranean as well as to the Adriatic Sea. However, species that have undergone tropicalization processes (i.e., shifts in range distribution induced by climate change) [41] were not included as NIS, and thus not considered in these analyses.
With regards to partly native and partly cryptogenic species, here defined as species that are native or cryptogenic in one EU region while they are non-indigenous (i.e., introduced by humans), in another EU region, they were included in the analyses at regional and/or subregional level but not at the pan-European level. Such NIS notably include Mediterranean molluscan transported with shellfish movements to the North-East Atlantic and vice versa, as well as also sessile biota, such as tunicates. Species native within a subregion (e.g., North Sea) that have been anthropogenically transferred to another country within the same subregion, were not included in the subregional analysis, although they are regarded as NIS in the countries they have invaded. This also applies to countries with coastal areas in more than one regional sea (Denmark, France, Germany, Spain, and Sweden).

2.3. Detection Year

The year of introduction was based on the reported date of the first collection/detection. However, it is important to point out that this date does not necessarily reflect the actual year of introduction which may have occurred years or even decades earlier since most species are often overlooked in the early stages of the invasion process, e.g., the green alga Codium fragile that has spread rapidly throughout the globe from its native range in Japan and the North Pacific was first detected in Europe c. 1900 in the Netherlands but reported in 1955 [42]. In addition, the date of first detection/collection is not always documented. In such cases, the publication date was accepted as the first record date. Moreover, in cases where only a time range has been supplied (e.g., 1986–1994), or the first record refers to a decade (e.g., the 1970s), the introduction date was set approximately as the average year for that given period (1990 and 1975, respectively).

3. Results

In total, 874 NIS were identified across European seas by December 2020 including 22 species of parasites and pathogens, and 50 species of microalgae (Table 2, Figure 2a). Of these 80% (701 taxa) were first reported in 1970. The vast majority of NIS are invertebrates (59%), followed by primary producers (algae and plants) (25%) and vertebrates (16%). Dissimilar proportions of all mentioned groups were evidenced across regions and subregions (Figure 3). While invertebrates dominate at all regional seas, the contribution of vertebrates (fishes) at the pan-European level is largely driven by the high contribution of Red Sea fish species in the Mediterranean Sea (Lessepsian immigrants) as opposed to their low presence in the NEA and Black Sea. Primary producers have a higher share in the NEA (29%) than the other regional seas (14–22%).
Table 2. List of NIS and their first year of detection at pan-European and regional levels. Group: VER = vertebrate, INV = invertebrate, PP = primary producer, INV/par = parasite, PP/micro = microalgae. BAL = Baltic Sea, NEA = North-East Atlantic Sea, MED = Mediterranean Sea, BLK = Black Sea. In bold, species detected since 1970. Asterisk denotes freshwater species detected in marine/estuarine environments.
Table 2. List of NIS and their first year of detection at pan-European and regional levels. Group: VER = vertebrate, INV = invertebrate, PP = primary producer, INV/par = parasite, PP/micro = microalgae. BAL = Baltic Sea, NEA = North-East Atlantic Sea, MED = Mediterranean Sea, BLK = Black Sea. In bold, species detected since 1970. Asterisk denotes freshwater species detected in marine/estuarine environments.
VERAblennes hians (Valenciennes, 1846)2018 2018
VERAbudefduf sexfasciatus (Lacepède, 1801)2017 2017
VERAbudefduf vaigiensis (Quoy & Gaimard, 1825)2005 2005
VERAbudefduf hoefleri (Steindachner, 1881)2014 2014
INVAcanthaster planci (Linnaeus, 1758)2006 2006
VERAcanthopagrus bifasciatus (Forsskål, 1775)2019 2019
PPAcanthosiphonia echinata (Harvey) A.M.Savoie & G.W.Saunders2018 2018
VERAcanthurus bahianus Castelnau, 18552013 2013
VERAcanthurus cfr gahhm (Forsskål, 1775)2019 2019
VERAcanthurus coeruleus Bloch & Schneider, 18012011 20132011
VERAcanthurus sohal (Forsskål, 1775)2017 2017
VERAcanthurus chirurgus (Bloch, 1787)2012 20132012
INVAcartia (Acanthacartia) tonsa Dana, 184919211921192119861976
INVAcartia (Acartiura) omorii Bradford, 19762004 2004
INVAchelia sawayai Marcus, 19402016 2016
VERAcipenser baerii Brandt, 1869196019601985
VERAcipenser gueldenstaedtii Brandt & Ratzeburg, 1833*196219622010
VERAcipenser ruthenus Linnaeus, 1758*18871887
VERAcipenser stellatus Pallas, 177119991999
VERAcipenser transmontanus Richardson, 18361999 1999
PPAcrochaetium catenulatum M.A.Howe1967 1967
PPAcrothamnion preissii (Sonder) E.M.Wollaston1968 20091968
INVActaeodes tomentosus (H. Milne Edwards, 1834)2013 2013
INVActeocina mucronata (Philippi, 1849)1991 1991
INVActumnus globulus Heller, 18611978 1978
PPAdelosina carinatastriata (Wiesner)2004 2004
PathogenAerococcus viridans Williams, Hirch & Cowan1961 1961
PPAgardhiella subulata (C.Agardh) Kraft & M.J.Wynne1984 19891984
PPAgarophyton vermiculophyllum (Ohmi) Gurgel, J.N.Norris & Fredericq1989200319892008
PPAglaothamnion halliae (Collins) Aponte, D.L.Ballantine & J.N.Norris1960 19602016
VERAgonus cataphractus (Linnaeus, 1758)2005 2005
PPAhnfeltiopsis flabelliformis (Harvey) Masuda, 19931994 1994
PP/microAkashiwo sanguinea (K.Hirasaka) G.Hansen & Ø.Moestrup1982 1982
VERAlepes djedaba (Forsskål, 1775)1960 1960
PP/microAlexandrium ostenfeldii (Paulsen) Balech & Tangen1986 1986
PP/microAlexandrium affine (H.Inoue & Y.Fukuyo) Balech1987 1987
PP/microAlexandrium leei Balech1991 1991
PP/microAlexandrium margalefii Balech2006 2006
PP/microAlexandrium taylori Balech1994 1994
INVAliculastrum cylindricum (Helbling, 1779)2020 2020
INV/parAllolepidapedon fistulariae Yamaguti, 19402005 2005
INVAlpheus rapacida de Man, 19081998 1998
INVAmathina tricarinata (Linnaeus, 1767)2012 2012
INVAmmothea hilgendorfi (Böhm, 1879)1979 20131979
INVAmpelisca cavicoxa Reid, 19512005 2005
INVAmpelisca heterodactyla Schellenberg, 19251986 1986
INVAmphibalanus eburneus (Gould, 1841)1818 187218181933
INVAmphibalanus reticulatus (Utinomi, 1967)1977 19971977
INVAmphibalanus variegatus (Darwin, 1854)1997 1997
INVAmphinome rostrata (Pallas, 1766) 1900 1900
PPAmphistegina cf. papillosa Said, 19492005 2005
PPAmphistegina lessonii d’Orbigny in Guérin-Méneville, 18322001 2001
PPAmphistegina lobifera Larsen, 19761959 1959
INVAmpithoe valida Smith, 18731985 19852000
INVAnadara kagoshimensis (Tokunaga, 1906)1966 199319661981
INVAnadara transversa (Say, 1822)1975 20161975
INV/parAnguillicola crassus (Kuwahara, Niimi & Itagaki, 1974)1980198819821980
INVAnomia chinensis Philippi, 18491974 1974
INVAnoplodactylus californicus Hall, 19121965 1965
PPAnotrichium furcellatum (J.Agardh) Baldock1950 1950
PPAntithamnion densum (Suhr) M.Howe1964 1964
PPAntithamnion diminuatum Wollaston1989 1989
PPAntithamnion hubbsii E.Y.Dawson1987 19891987
PPAntithamnion amphigeneum A.J.K.Millar1992 19951992
PPAntithamnionella ternifolia (Hooker fil. & Harvey) Lyle1910201419101981
INVAoroides curvipes Ariyama, 20042009 2009
INVAoroides semicurvatus Ariyama, 20042009 2009
INVAoroides longimerus Ren & Zheng, 19962013 20132015
INVApanthura addui Wägele, 19811998 1998
INVAplidium antillense (Gravier, 1955)2004 2004
INVAplidium accarense (Millar, 1953)2012 2012
VERApogonichthyoides pharaonis (Bellotti, 1874)1964 1964
INVAquilonastra burtoni (Gray, 1840)2003 2003
INVArachnidium lacourti d’Hondt & Faasse, 2006199920151999
INVArachnoidella protecta Harmer, 19151992 1992
INVArbopercula tenella (Hincks, 1880)1990 1990
INVArctapodema australis (Vanhöffen, 1912)1967 1967
INVArcuatula senhousia (Benson, 1842)1982 200219822002
INVArgopecten gibbus (Linnaeus, 1758)2016 2016
INVArhynchite arhynchite (Ikeda, 1924)2001 2001
INVArietellus pavoninus Sars G.O., 19051967 1967
VERArothron hispidus (Linnaeus, 1758)2018 2018
INVArtemia monica Verrill, 18691972 19871972
INVAscidia curvata (Traustedt, 1882)2014 2014
INVAscidia interrupta Heller, 18781990 1990
INVAsclerocheilus ashworthi Blake, 19812005 2005
PPAscophyllum nodosum (Linnaeus) Le Jolis2009 2009
PPAsparagopsis taxiformis (Delile) Trevisan de Saint-Léon (lineage 2)1928 19281992
PPAsparagopsis armata Harvey1880 19221880
INVAsterocarpa humilis (Heller, 1878)2005 2005
PP/microAsteromphalus sarcophagus Wallich, 18601993 1993
INVAtactodea striata (Gmelin, 1791)1977 1977
INVAtergatis roseus (Rüppell, 1830)2009 2009
VERAtherinomorus forskalii (Rüppell, 1838)1929 1929
INVAtys angustatus E. A. Smith, 18722017 2017
INVAtys ehrenbergi (Issel, 1869)2016 2016
INVAurelia coerulea von Lendenfeld, 18842002 2002
INVAurelia solida Browne, 19052000 2000
INVAustrominius modestus (Darwin, 1854)1944 19441990
INVAxionice medusa (Savigny in Lamarck, 1818)1976 1976
INVBaeolidia moebii Bergh, 18882017 2017
INVBalanus glandula Darwin, 18542015 2015
INVBalanus trigonus Darwin, 18541887 18871927
VERBalistoides conspicillum (Bloch & Schneider, 1801)2012 2012
INVBankia fimbriatula Moll & Roch, 19311847 1847
INVBarentsia ramosa (Robertson, 1900)1962 1962
PPBatophora occidentalis var. largoensis (Harvey) S.Berger & Kaever ex M.J.Wynne2020 2020
INVBeania maxilladentata Ramalho, Muricy &
Taylor, 2010
2013 2013
INVBemlos leptocheirus (Walker, 1909)2015 2015
INVBeroe ovata Bruguière, 178919972011201320041997
INVBerthellina citrina (Rüppell & Leuckart, 1828)2019 2019
PP/microBiddulphia rhombus (Ehrenberg) W.Smith1983 1983
PP/microBiddulphia sinensis Greville190319041903
INVBiflustra grandicella (Canu & Bassler, 1929)2016 2016
INVBispira polyomma Giangrande & Faasse, 20122010 20102014
INVBiuve fulvipunctata (Baba, 1938)1993 1993
INVBoccardia proboscidea Hartman, 19401996 19962014
INVBoccardia semibranchiata Guérin, 19901999 1999
INVBoccardiella hamata (Webster, 1879)2001 2001
PathogenBonamia exitiosa Hine, Cochennac & Berthe2006 20062007
PathogenBonamia ostreae Pichot, Comps, Tigé, Grizel & Rabouin1978 19781990
PPBonnemaisonia hamifera Hariot1898190018981932
INVBostrycapulus odites Collin, 20051973 1973
INVBotrylloides diegensis Ritter & Forsyth, 19171999 19992004
INVBotrylloides giganteum (Pérès, 1949)2003 2003
INVBotrylloides niger Herdman, 18862013 20132014
INVBotrylloides violaceus Oka, 19271991 19991991
PPBotryocladia wrightii (Harvey) W.E.Schmidt, D.L.Ballantine & Fredericq1978 20051978
PPBotryocladia madagascariensis G.Feldmann1978 1978
PPBotrytella parva (Takamatsu) H.S.Kim1996 1996
INVBougainvillia macloviana Lesson, 18301895 1895
INVBrachidontes exustus (Linnaeus, 1758)1977 1977
INVBrachidontes pharaonis (P. Fischer, 1870)1960 1960
INVBranchiomma bairdi (McIntsosh, 1885)1998 20121998
INVBranchiomma boholense (Grube, 1878)2004 2004
INVBranchiomma luctuosum (Grube, 1870)1978 20151978
VERBregmaceros nectabanus Whitley, 19412014 2014
INVBugulina simplex (Hincks, 1886)1982 1982
INVBugulina stolonifera (Ryland, 1960)1976 1976
INVBulla arabica Malaquias & Reid, 20081998 1998
INVBursatella leachii Blainville, 18171969 1969
INVCalanopia elliptica (Dana, 1849)1891 1891
INVCallinectes danae Smith, 18691981 1981
INVCallinectes pallidus (de Rochebrune, 1883)2013 2013
INVCallinectes sapidus Rathbun, 189619011951190119471967
VERCallionymus filamentosus Valenciennes, 18372003 2003
INVCalyptospadix cerulea Clarke, 188219402014 19781940
VERCantherhines pullus (Ranzani, 1842)2015 2015
INVCaprella mutica Schurin, 1935198520171985
INVCaprella scaura Templeton, 18361985 19851994
VERCarassius auratus (Linnaeus, 1758)2012 2012
VERCarassius gibelio (Bloch, 1782)*18001800
INVCarijoa riisei (Duchassaing & Michelotti, 1860)2016 2016
INVCarupa tenuipes Dana, 18522009 2009
INVCassiopea andromeda (Forsskål, 1775)1903 1903
PPCaulacanthus okamurae Yamada1999 19992002
PPCaulerpa cylindracea Sonder1991 19971991
PPCaulerpa lamourouxii (Turner) C.Agardh1956 1956
PPCaulerpa taxifolia (M.Vahl) C.Agardh1984 1984
PPCaulerpa taxifolia var. distichophylla (Sonder) Verlaque, Huisman & Procaccini2007 2007
PPCaulerpa webbiana Montagne2002 2002
INVCaulibugula zanzibariensis (Waters, 1913)2003 2003
INVCellana rota (Gmelin, 1791)2007 2007
INVCelleporaria inaudita Tilbrook, Hayward &
Gordon, 2001
2007 2007
INVCelleporaria aperta (Hincks, 1882)1975 1975
INVCelleporaria brunnea (Hincks, 1884)2007 20072010
INVCelleporaria vermiformis (Waters, 1909)2015 2015
INVCelleporella carolinensis Ryland, 19791993 1993
INVCeltodoryx ciocalyptoides (Burton, 1935)1996 1996
INVCentropages furcatus (Dana, 1849)1988 1988
VERCephalopholis hemistiktos (Rüppell, 1830)2009 2009
VERCephalopholis taeniops (Valenciennes, 1828)2009 2009
VERCephalopholis nigri (Günther, 1859)2016 2016
INVCephalothrix simula Iwata, 19522012 2012
PPCeramium atrorubescens Kylin1988 1988
PPCeramium sungminbooi Hughey & Boo2018 2018
PPCeramium tenuicorne (Kützing) Waern2011 2011
PPCeramium bisporum D.L.Ballantine1980 1980
PPCeramium strobiliforme G.W.Lawson & D.M.John1991 1991
INVCeratonereis mirabilis Kinberg, 18651997 1997
INVCerithidium perparvulum (Watson, 1886)1995 1995
INVCerithiopsis pulvis (Issel, 1869)1985 1985
INVCerithiopsis tenthrenois (Melvill, 1896)1985 1985
INVCerithium scabridum Philippi, 18481972 1972
PP/microChaetoceros peruvianus Brightwell1981 1981
PP/microChaetoceros rostratus Ralfs2003 2003
PP/microChaetoceros bacteriastroides G.H.H.Karsten1996 1996
PP/microChaetoceros concavicornis Mangin2011 2011
PP/microChaetoceros pseudosymmetricus Nielsen2015 2015
VERChaetodipterus faber (Broussonet, 1782)2019 2019
VERChaetodon sanctaehelenae Günther, 18681993 1993
VERChaetodon auriga Forsskål, 17752015 2015
VERChaetodontoplus septentrionalis (Temminck & Schlegel, 1844)2015 2015
INVChaetopleura angulata (Spengler, 1797)1850 1850
INVChaetozone corona Berkeley & Berkeley, 19411982 19961982
INVChama asperella Lamarck, 18192007 2007
INVChama pacifica Broderip, 18351998 1998
VERChampsodon nudivittis (Ogilby, 1895)2012 2012
INVCharybdis (Charybdis) japonica (A. Milne-Edwards, 1861)2006 2006
INVCharybdis (Charybdis) feriata (Linnaeus, 1758)2004 2004
INVCharybdis (Charybdis) hellerii (A. Milne-Edwards, 1867)1998 1998
INVCharybdis (Charybdis) lucifera (Fabricius, 1798)2006 2006
INVCharybdis (Goniohellenus) longicollis Leene, 19381969 1969
PP/microChattonella marina (Subrahmanyan) Hara &
1974 1974
VERCheilodipterus novemstriatus (Rüppell, 1838)2015 2015
INVChelicorophium robustum (G.O. Sars, 1895)20182018
INVChelicorophium curvispinum (G.O. Sars, 1895)191219211912
VERChlorurus rhakoura Randall & Anderson, 19972017 2017
PPChondria pygmaea Garbary & Vandermeulen1974 1974
PPChondria curvilineata F.S.Collins & Hervey1981 1981
PPChondrus giganteus f. flabellatus Mikami1994 1994
VERChromis multilineata (Guichenot, 1853)2015 2015
INVChromodoris quadricolor (Rüppell & Leuckart, 1830)1982 1982
INVChrysaora achlyos Martin, Gershwin, Burnett, Cargo & Bloom, 19972018 2018
VERChrysiptera cyanea (Quoy & Gaimard, 1825)2013 2013
VERChrysiptera hemicyanea (Weber, 1913)2017 2017
PPChrysonephos lewisii (W.R.Taylor) W.R.Taylor1988 1988
INVCingulina isseli (Tryon, 1886)1998 1998
INVCiona robusta Hoshino & Tokioka, 19671901 20071901
VERCirrhitus atlanticus Osório, 18932018 2018
PPCladophora patentiramea (Montagne) Kützing1991 1991
INVClavelina oblonga Herdman, 18801929 19711929
PathogenClaviceps purpurea (Fr.:Fr.)Tul.1960 1960
PPClavulina cf. multicamerata Chapman, 19072012 2012
INVClementia papyracea (Gmelin, 1791)1985 1985
INVClymenella torquata (Leidy, 1855)1977 1977
INVClytia gregaria (Agassiz, 1862)2017 2017
INVClytia hummelincki (Leloup, 1935)1996 1996
INVClytia linearis (Thorneley, 1900)1951 19831951
PPCodium arabicum Kützing2006 2006
PPCodium fragile subsp. fragile (Suringar) Hariot1895191918951946
PPColaconema codicola (Børgesen) H.Stegenga, J.J.
Bolton & R.J.Anderson
1926 19261952
PPColaconema dasyae (F.S.Collins) Stegenga, I.Mol, Prud’homme van Reine & Lokhorst1951 1951
INVColeusia signata (Paul’son, 1875)2005 2005
PPColpomenia peregrina Sauvageau1905 19051918
INVConomurex persicus (Swainson, 1821)1983 1983
INVCorambe obscura (A.E. Verrill, 1870)1879 1879 1986
INVCorbicula fluminea (O. F. Müller, 1774)1978 1978
INVCorella eumyota Traustedt, 18822002 2002
PP/microCorymbellus aureus J.C.Green1992 1992
PPCorynomorpha prismatica (J.Agardh) J.Agardh1990 1990
PPCorynophlaea verruculiformis (Y.-P.Lee & I.K.Lee) Y.-P.Lee1994 1994
INVCoryphellina rubrolineata O’Donoghue, 19292008 2008
INVCrassostrea rhizophorae (Guilding, 1828)1976 1976
INVCrassostrea virginica (Gmelin, 1791)1861 1861 1974
INVCrepidacantha poissonii (Audouin, 1826)1982 1982
INVCrepidula fornicata (Linnaeus, 1758)1902 19021957
INVCrepipatella dilatata (Lamarck, 1822)2005 20052014
INVCrisularia plumosa (Pallas, 1766)1937 1937
INVCrisularia serrata (Lamarck, 1816)1902 1902
PPCryptonemia hibernica Guiry & L.M.Irvine1911 1911
PPCushmanina striatopunctata (Parker & Jones, 1865)1913 1913
INVCuthona perca (Er. Marcus, 1958)1976 1976
INVCycloscala hyalina (G. B. Sowerby II, 1844)1992 1992
INVCymodoce fuscina Schotte & Kensley, 20052015 2015
VERCynoscion regalis (Bloch & Schneider, 1801)2009 2009
VERCyprinus carpio (Linnaeus, 1758)*120012001879
PPDasya sessilis Yamada1984 19891984
PPDasysiphonia japonica (Yendo) H.-S.Kim1984 19841998
INVDendostrea frons (Linnaeus, 1758)1983 1983
INVDendostrea folium (Linnaeus, 1758)2005 2005
PPDerbesia rhizophora Yamada1984 1984
INVDesdemona ornata Banse, 19571983 19931983
INVDiadema setosum (Leske, 1778)2010 2010
INVDiadumene lineata (Verrill, 1869)19252011196319251945
PP/microDicroerisma psilonereiella F.J.R.Taylor & S.A.
1998 1998
PPDictyota cyanoloma Tronholm, De Clerck, A.Gómez-Garreta & Rull Lluch in Tronholm et al.1935 20061935
INVDidemnum perlucidum Monniot F., 19832006 2006
INVDidemnum vexillum Kott, 20021968 19682007
INVDikerogammarus villosus (Sowinsky, 1894)20152015
INVDikoleps micalii Agamennone, Sbrana, Nardi, Siragusa & Germanà, 20202016 2016
PP/microDinophysis sacculus Stein2004 2004
INVDiodora funiculata (Reeve, 1850)2013 2013
INVDiplosoma listerianum (Milne Edwards, 1841)1877 1877
INVDipolydora quadrilobata (Jacobi, 1883)2003 2003
INVDipolydora socialis (Schmarda, 1861)2006 2006
INVDipolydora tentaculata (Blake & Kudenov, 1978)2005 2005
PPDipterosiphonia dendritica (C.Agardh) F.Schmitz1961 1961
INVDispio magna (Day, 1955)1982 1982
PP/microDissodinium pseudocalani (Gonnert) Drebes ex Elbrachter & Drebes2003 2003
INVDistaplia magnilarva (Della Valle, 1881)1929 1929
INVDistaplia bermudensis Van Name, 19021953 20061953
INVDistaplia corolla Monniot F., 19741971 1971
INVDodecaceria capensis Day, 19611976 1976
INVDorvillea similis (Crossland, 1924)2014 2014
INVDreissena rostriformis bugensis (Andrusov, 1897)20142014
VERDussumieria elopsoides Bleeker, 18492005 2005
INVDyspanopeus texanus (Stimpson, 1859)2015 2015
INVDyspanopeus sayi (Smith, 1869)1992 20071992
INVEchinogammarus trichiatus (Martynov, 1932)20142014
INVEcteinascidia styeloides (Traustedt, 1882)1983 1983
INVEctopleura crocea (Agassiz, 1862)1895 19891895
INVEdwardsiella lineata (Verrill in Baird, 1873)2010 2010
PPElachista spp mentioned as E. flaccida1993 1993
VERElates ransonnettii (Steindachner, 1876)2005 2005
PPElodea canadensis Michx.*18731873
PPElodea nuttallii (Planch.) H.St.John199119912006
PPElphidium striatopunctatum (Fichtel & Moll, 1798)1911 1911
INVElysia nealae (Ostergaard, 1955)2018 2018
PP/microEmiliania huxleyi (Lohmann) W.W.Hay & H.P.Mohler1989 1989
INVEndeis biseriata Stock, 19681979 1979
INVEnsis leei M. Huber, 2015197819911978
INVEocuma dimorphum Fage, 19281992 1992
INVEocuma sarsii (Kossmann), 18801901 1901
VEREpinephelus fasciatus (Forsskål, 1775)2018 2018
VEREpinephelus coioides (Hamilton, 1822)1998 1998
VEREpinephelus malabaricus (Bloch & Schneider, 1801)2011 2011
VEREpinephelus merra Bloch, 17932004 2004
VEREquulites klunzingeri (Steindachner, 1898)1955 1955
INVErgalatax junionae Houart, 20081993 1993
INVEriocheir sinensis H. Milne Edwards, 1853*19121921191219591997
INVErugosquilla massavensis (Kossmann, 1880)1956 1956
PP/microEthmodiscus punctiger Castracane180019791800
VEREtrumeus golanii DiBattista, Randall & Bowen, 20121999 1999
INVEuchaeta concinna Dana, 18491987 1987
INVEucheilota paradoxica Mayer, 19001967 1967
INVEuchone limnicola Reish, 19592015 2015
INVEucidaris tribuloides (Lamarck, 1816)1998 1998
INVEudendrium carneum Clarke, 18821950 1950
INVEudendrium merulum Watson, 19851969 1969
INVEunaticina papilla (Gmelin, 1791)2020 2020
INVEuplana gracilis Girard, 18532002 2002
INVEuplokamis dunlapae Mills, 19872011 2011
PP/microEupyxidicula turris (Greville) S.Blanco & C.E.
1983 1983
INVEurypanopeus depressus (Smith, 1869)2009 2009
INVEurytemora americana Williams, 19061938 1938
INVEurytemora carolleeae Alekseev & Souissi, 2011201120122011
INVEurytemora pacifica Sato, 19132014 2014
INVEurythoe laevisetis Fauvel, 19142011 2011
INVEusarsiella zostericola (Cushman, 1906)2012 2012
INVEusyllis kupfferi Langerhans, 18791998 1998
INVEuthymella colzumensis (Jousseaume, 1898)2017 2017
PP/microEutintinnus lusus-undae (Entz)2001 2001
INVFauveliopsis glabra (Hartman, 1960)2007 2007
INVFavorinus ghanensis Edmunds, 19682020 2020
INVFaxonius limosus (Rafinesque, 1817)20152015
INVFenestrulina malusii (Audouin, 1826)2011 2011
INVFenestrulina delicia Winston, Hayward & Craig, 20002002 2002
INVFerosagitta galerita (Dallot, 1971)2011 2011
PP/microFibrocapsa japonica S.Toriumi & H.Takano1924 1924
INVFicopomatus enigmaticus (Fauvel, 1923)19191939192119191935
INVFinella pupoides A. Adams, 18601996 1996
VERFistularia petimba Lacepède, 18032018 2018
VERFistularia commersonii Rüppell, 18381999 1999
INVFistulobalanus albicostatus (Pilsbry, 1916)1973 1973
INVFulvia fragilis (Forsskål in Niebuhr, 1775)1983 1983
VERFundulus heteroclitus heteroclitus (Linnaeus, 1766)1970 19702005
INVGafrarium savignyi (Jonas, 1846)2005 2005
INVGammarus tigrinus Sexton, 1939193119751931
PPGelidium microdonticum W.R.Taylor2017 2017
PPGelidium vagum Okamura2010 2010
VERGenyatremus cavifrons (Cuvier, 1830)2015 2015
INVGlabropilumnus laevis (Dana, 1852)1956 1956
INVGlycinde bonhourei Gravier, 19042007 2007
VERGobiosoma bosc (Lacepède, 1800)2009 2009
INVGodiva quadricolor (Barnard, 1927)1985 1985
INVGoniadella gracilis (Verrill, 1873)1968 1968
INVGoniobranchus annulatus (Eliot, 1904)2004 2004
INVGoniobranchus obsoletus (Rüppell & Leuckart, 1830)2018 2018
INVGonioinfradens giardi (Nobili, 1905)2010 2010
INVGonionemus vertens A. Agassiz, 18621700 17001918
PPGoniotrichopsis sublittoralis G.M.Smith1975 19751989
PPGracilariopsis chorda (Holmes) Ohmi2010 2010
INVGrandidierella japonica Stephensen, 19382010201020102013
PPGrateloupia imbricata Holmes2005 2005
PPGrateloupia asiatica S.Kawaguchi & H.W.Wang1984 1984
PPGrateloupia patens (Okamura) S.Kawaguchi & H.W.Wang1994 1994
PPGrateloupia subpectinata Holmes1978 19781990
PPGrateloupia turuturu Yamada1982 19891982
PPGrateloupia yinggehaiensis H.W.Wang & R.X.Luan2008 2008
INVGuinearma alberti (Rathbun, 1921)2016 2016
VERGymnomuraena zebra (Shaw, 1797)2002 2002
PPGymnophycus hapsiphorus Huisman & Kraft2011 2011
INV/parGyrodactylus salaris Malmberg, 19571975 1975
PP/microGyrodinium corallinum Kofoid & Swezy2001 2001
INVHalgerda willeyi Eliot, 19041988 1988
INVHaliclona (Halichoclona) vansoesti de Weerdt, de Kluijver & Gómez, 19992019 2019
INVHaliclystus tenuis Kishinouye, 19102010 2010
PPHalimeda incrassata (J.Ellis) J.V.Lamouroux2011 2011
INVHaliotis discus hannai Ino, 19531985 1985
INVHaloa japonica (Pilsbry, 1895)1992 19921992
PPHalophila stipulacea (Forsskål) Ascherson1894 1894
INVHaminella solitaria (Say, 1822)201620162020
PathogenHaplosporidium nelsoni Haskin, Stauber & Mackin1975 1975
INVHeleobia charruana (d’Orbigny, 1841)2014 2014
INVHeliacus implexus (Mighels, 1845)2019 2019
INVHemigrapsus sanguineus (De Haan, 1835)1999 199919992008
INVHemigrapsus takanoi Asakura & Watanabe, 2005199320141993
INVHemimysis anomala G.O. Sars, 1907*1962196219992007
VERHemiramphus far (Forsskål, 1775)1943 1943
VERHeniochus acuminatus (Linnaeus, 1758)2014 2014
VERHeniochus intermedius Steindachner, 18932013 20132014
INVHerbstia nitida Manning & Holthuis, 19812002 2002
INVHerdmania momus (Savigny, 1816)1998 1998
PPHerposiphonia parca Setchell1997 20061997
INVHesperibalanus fallax (Broch, 1927)1976 19761976
PPHeterostegina depressa d’Orbigny, 18261988 1988
INVHeterotentacula mirabilis (Kramp, 1957)1997 1997
PPHildenbrandia occidentalis Setch.2011 2011
VERHippocampus kuda Bleeker, 18522014 2014
INVHippopodina feegeensis (Busk, 1884)1996 1996
VERHolacanthus africanus Cadenat, 19512017 20182017
VERHolacanthus ciliaris (Linnaeus, 1758)2011 2011
VERHolocentrus adscensionis (Osbeck, 1765)2016 2016
INVHomarus americanus H. Milne Edwards, 18371961200719612018
VERHuso huso (Linnaeus, 1758)*19621962
PPHydroclathrus tilesii (Endlicher) Santiañez & M.J.Wynne2006 2006
INVHydroides brachyacantha Rioja, 19412015 2015
INVHydroides dirampha Mörch, 18631981 19821981
INVHydroides elegans (Haswell, 1883)1868 19731868
INVHydroides ezoensis Okuda, 19341968 1968
INVHydroides heterocera (Grube, 1868)1998 1998
INVHymeniacidon gracilis (Hentschel, 1912)2017 2017
INVHypania invalida (Grube, 1860)1995 1995
INVHypereteone heteropoda (Hartman, 1951)2017 2017
PPHypnea musciformis (Wulfen) J.V.Lamouroux2005 2005
PPHypnea anastomosans Papenfuss, Lipkin & P.C.Silva2008 2008
PPHypnea cervicornis J.Agardh2009 2009
PPHypnea cornuta (Kützing) J.Agardh1894 1894
PPHypnea spinella (C.Agardh) Kützing1977 1977
PPHypnea valentiae (Turner) Montagne1996 20061996
INVHypselodoris infucata (Rüppell & Leuckart, 1830)2002 2002
INVIaniropsis serricaudis Gurjanova, 19362000 20002012
INVIncisocalliope aestuarius (Watling & Maurer, 1973)1975 1975
INVIndothais lacera (Born, 1778)1983 1983
INVIsognomon aff. australicus (Reeve, 1858)2016 2016
INVIsognomon legumen (Gmelin, 1791)2016 2016
INVIsognomon radiatus (Anton, 1838)1996 1996
INVIsolda pulchella Müller in Grube, 18581994 1994
INVIxa monodi Holthuis & Gottlieb, 19561999 1999
INVJasus lalandii (H. Milne Edwards, 1837)1980 1980
PPKapraunia schneideri (Stuercke & Freshwater) A.M.Savoie & G.W.Saunders2010 20102016
PP/microKarenia longicanalis Z.B.Yang, I.J.Hodgkiss & Gerd Hansen2008 2008
PP/microKarenia mikimotoi (Miyake & Kominami ex Oda) Gert Hansen & Ø.Moestrup196819801968
PP/microKarenia papilionacea A.J.Haywood & K.A.Steidinger1994 1994
INVKoinostylochus ostreophagus (Hyman, 1955)1970 1970
PathogenLabyrinthula zosterae D. Porter & Muehlst. in Muehlstein & Short1930 1930
VERLactophrys triqueter (Linnaeus, 1758)1909 1909
VERLagocephalus guentheri Miranda Ribeiro, 19151952 1952
VERLagocephalus sceleratus (Gmelin, 1789)2004 2004
VERLagocephalus suezensis Clark & Gohar, 19532003 2003
INVLamprohaminoea ovalis (Pease, 1868)2001 2001
INVLaonome xeprovala Bick & Bastrop, in Bick et al., 2018201220122016 2018
INVLatopilumnus malardi (De Man, 1914)1910 1910
PP/microLauderia pumila Castracane1995 1995
PPLaurencia brongniartii J.Agardh1989 1989
PPLaurencia caduciramulosa Masuda & Kawaguchi1991 1991
PPLaurencia okamurae Yamada1984 1984
PPLeathesia marina (Lyngbye) Decaisne1905 1905
INVLeiocapitellides analis Hartmann-Schröder, 19602000 2000
INVLeiochrides australis Augener, 19142002 2002
PP/microLennoxia faveolata H.A.Thomsen & K.R.Buck20072007
INVLeonnates persicus Wesenberg-Lund, 19492013 2013
INVLepidonotus tenuisetosus (Gravier, 1902)2007 2007
INVLepidonotus carinulatus (Grube, 1870)1984 1984
INVLeucotina natalensis E. A. Smith, 19101996 1996
INVLimnodrilus profundicola (Verrill, 1871)20142014
INVLimulus polyphemus (Linnaeus, 1758)1866 1866
INVLinguimaera caesaris Krapp-Schickel, 20031997 1997
INVLinopherus canariensis Langerhans, 18811997 1997
INVLioberus ligneus (Reeve, 1858)2019 2019
PPLithophyllum yessoense Foslie1994 1994
PPLomentaria flaccida Tanaka2002 2002
PPLomentaria hakodatensis Yendo1978 19841978
PPLophocladia lallemandii (Montagne) F.Schmitz1908 1908
INVLottia sp.2015 2015
INVLovenella assimilis (Browne, 1905)2007 2007
INVLumbrinerides crassicephala (Hartman, 1965)1994 1994
INVLumbrinerides neogesae Miura, 19812002 2002
INVLumbrineris perkinsi Carrera-Parra, 20011973 1973
VERLutjanus argentimaculatus (Forsskål, 1775)2019 2019
VERLutjanus griseus (Linnaeus, 1758)2018 2018
VERLutjanus jocu (Bloch & Schneider, 1801)2005 2005
VERLutjanus sebae (Cuvier, 1816)2010 2010
VERLutjanus fulviflamma (Forsskål, 1775)2013 2013
INVLysidice collaris Grube, 18701961 1961
PPMacrocystis pyrifera (Linnaeus) C.Agardh1972 1972
INVMacromedaeus voeltzkowi (Lenz, 1905)1910 1910
INVMacrophthalmus (Macrophthalmus) indicus
Davie, 2012
2009 2009
INVMacrorhynchia philippina Kirchenpauer, 18721982 1982
INVMagallana angulata (Lamarck, 1819)1700 1700
INVMagallana gigas (Thunberg, 1793)17002019170018502010
INVMagallana rivularis (Gould, 1861)1994 1994
INVMagallana sikamea (Amemiya, 1928)1994 1994
INVMalleus regula (Forsskål in Niebuhr, 1775)1970 1970
INVMarenzelleria arctia (Chamberlin, 1920)20042004
INVMarenzelleria neglecta Sikorski & Bick, 2004198319831985
INVMarenzelleria viridis (Verrill, 1873)198319851983
INVMarginella glabella (Linnaeus, 1758)2009 2009
INVMaritigrella fuscopunctata (Prudhoe, 1978)2014 2014
INVMarivagia stellata Galil & Gershwin, 20102019 2019
INVMarphysa victori Lavesque, Daffe, Bonifácio & Hutchings, 20171975 1975
PathogenMarteilia refringens Grizel, Comps, Bonami, Cousserans, Duthoit & Le Pennec1975 19751992
INVMatuta victor (J.C. Fabricius, 1781)2018 2018
PP/microMediopyxis helysia Kühn, Hargreaves & Halliger2003 2003
INVMegabalanus tintinnabulum (Linnaeus, 1758)1764 17641971
INVMegabalanus coccopoma (Darwin, 1854)1851 1851
INVMelanella orientalis Agamennone, Micali &
Siragusa, 2020
2016 2016
PPMelanothamnus flavimarinus (M.-S.Kim & I.K.Lee) Díaz-Tapia & Maggs2010 2010
PPMelanothamnus harveyi (Bailey) Díaz-Tapia & Maggs1958198220151958
PPMelanothamnus japonicus (Harvey) Díaz-Tapia & Maggs2016 2016
INVMelibe viridis (Kelaart, 1858)1970 1970
INVMelita nitida S.I. Smith in Verrill, 1873199620101996
INVMenaethius monoceros (Latreille, 1825)1978 1978
INVMercenaria mercenaria (Linnaeus, 1758)1861 18611964
INVMesanthura cfr. romulea Poore & Lew Ton, 19862000 2000
INVMetacalanus acutioperculum Ohtsuka, 19841995 1995
INVMetacirolana rotunda (Bruce & Jones, 1978)1998 1998
INVMetapenaeopsis aegyptia Galil & Golani, 19901996 1996
INVMetapenaeopsis mogiensis consobrina (Nobili, 1904)1995 1995
INVMetapenaeus monoceros (Fabricius, 1798)1961 1961
INVMetaxia bacillum (Issel, 1869)1995 1995
INVMicrocosmus anchylodeirus Traustedt, 18831980 1980
INVMicrocosmus squamiger Michaelsen, 19271971 19921971
INVMicrocosmus exasperatus Heller, 18782005 20052014
VERMicropogonias undulatus (Linnaeus, 1766)1998 1998
PPMiliolinella fichteliana (d’Orbigny, 1839)1911 1911
INVMillepora alcicornis Linnaeus, 17582004 2004
PPMimosina affinis Millett, 19002012 2012
INVMitrella psilla (Duclos, 1846)2016 2016
INVMizuhopecten yessoensis (Jay, 1857)1979 1979
INVMnemiopsis leidyi A. Agassiz, 186519862006200119901986
INVMnestia girardi (Audouin, 1826)1990 1990
INVMoerisia inkermanica Paltschikowa-Ostroumowa195920181959
INVMolgula occidentalis Traustedt, 18832010 2010
INVMonocorophium uenoi (Stephensen, 1932)2007 2007
VERMorone saxatilis x Morone chrysops2019 2019
INVMulinia lateralis (Say, 1822)2017 2017
INVMurchisonellidae T. L. Casey, 190420132013
INVMycale (Carmia) senegalensis Lévi, 19522002 2002
VERMycteroperca tigris (Valenciennes, 1833)2018 2018
INV/parMyicola ostreae Hoshina & Sugiura, 19531972 19721972
INVMyra subgranulata Kossmann, 18772004 2004
INV/parMytilicola orientalis Mori, 19351977201819771977
INVMytilopsis leucophaeata (Conrad, 1831)183519281835
INVNaineris setosa (Verrill, 1900)2010 2010
INVNamanereis littoralis (Grube, 1872)1991 1991
INVNeanthes agulhana (Day, 1963)2007 2007
PPNemalion vermiculare Suringar2005 2005
VERNemipterus randalli Russell, 19862014 2014
INVNemopsis bachei L. Agassiz, 18491905 1905
INVNeodexiospira brasiliensis (Grube, 1872)1982 1982
PPNeogastroclonium subarticulatum (Turner)
L.Le Gall, Dalen & G.W.Saunders
2017 2017
VERNeogobius melanostomus (Pallas, 1814)199019902004
PPNeoizziella divaricata (C.K.Tseng) S.-M.Lin, S.-Y.Yang & Huisman1989 1989
INVNeomysis americana (S.I. Smith, 1873)2010 2010
INVNereis jacksoni Kinberg, 18651964 1964
INVNerita sanguinolenta Menke, 18291969 1969
INVNippoleucon hinumensis (Gamô, 1967)20192019
PPNitophyllum stellato-corticatum Okamura1984 1984
PPNonionella sp. T1/Nonionella stella2012 2012
INVNotocochlis gualtieriana (Récluz, 1844)1978 1978
INVNotomastus aberans Day, 19571964 1964
INVNotomastus mossambicus (Thomassin, 1970)1997 1997
INVNovafabricia infratorquata (Fitzhugh, 1973)1985 20131985
INV/parNybelinia africana Dollfus, 19602005 2005
INVObesogammarus crassus (Sars G.O., 1894)*196219622016
INVOcinebrellus inornatus (Récluz, 1851)1993 1993
INVOdontodactylus scyllarus (Linnaeus, 1758)2009 2009
INVOithona davisae Ferrari F.D. & Orsi, 19842000 200220002009
VEROncorhynchus gorbuscha (Walbaum, 1792)195819581958
VEROncorhynchus kisutch (Walbaum, 1792)*190519841905
VEROncorhynchus mykiss (Walbaum, 1792)*188218821899
PPOperculina ammonoides (Gronovius, 1781)1911 1911
INVOphiactis macrolepidota Marktanner-Turneretscher, 18871998 1998
INVOphiactis savignyi (Müller & Troschel, 1842)1968 1968
VEROphioblennius atlanticus (Valenciennes, 1836)2017 2017
INVOphryotrocha japonica Paxton & Åkesson, 20101999 1999
INVOphryotrocha diadema Åkesson, 19762006 2006
VEROplegnathus fasciatus (Temminck & Schlegel, 1844)2009 2009
VEROrthopristis chrysoptera (Linnaeus, 1766)2020 2020
INVOscilla galilae Bogi, Karhan & Yokeş, 20122016 2016
VEROstorhinchus fasciatus (White, 1790)2014 2014
PathogenOstracoblabe implexa Born & Flahault1951 1951
INVOstraea angasi G. B. Sowerby II, 18711985 1985
INVOstrea equestris Say, 18341995 1995
INVOstrea denselamellosa Lischke, 18691982 1982
INVOstrea puelchana d’Orbigny, 18421989 1989
INVOulastrea crispata (Lamarck, 1816)2012 2012
INVOxydromus humesi (Pettibone, 1961)2009 2009
PP/microOxytoxum criophilum Balech2003 2003
VEROxyurichthys papuensis (Valenciennes, 1837)2010 2010
INVPachygrapsus gracilis (de Saussure, 1857)2013 2013
PPPachymeniopsis gargiuli S.Y.Kim, Manghisi,
Morabito & S.M.Boo
1968 20011968
PPPachymeniopsis lanceolata (K.Okamura) Y.Yamada ex S.Kawabata1982 20061982
INVPacifastacus leniusculus (Dana, 1852)20142014
INVPacificincola perforata (Okada & Mawatari, 1937)2001 2001
PPPadina boergesenii Allender & Kraft1965 1965
VERPagrus major (Temminck & Schlegel, 1843)2004 2004
INVPagurus longicarpus (Say, 1817)2020 2020
INVPalaemon macrodactylus Rathbun, 190219982014199820052002
INVPalola valida (Gravier, 1900)2014 2014
VERPampus argenteus (Euphrasen, 1788)1896 1896
INVPanopeus occidentalis Saussure, 18572015 2015
PPPapenfussiella kuromo (Yendo) Inagaki1990 1990
INVParacalanus quasimodo Bowman, 19712017 2017
INVParacaprella pusilla Mayer, 18902010 20102011
INVParacerceis sculpta (Holmes, 1904)1981 19881981
INVParadella dianae (Menzies, 1962)1985 19881985
INVParadyte cf. crinoidicola (Potts, 1910)1968 1968
INVParaleucilla magna Klautau, Monteiro &
Borojevic, 2004
2000 20062000
INVParalithodes camtschaticus (Tilesius, 1815)2008 2008
INVParametopella cypris Holmes, 19052014 2014
INVParamysis (Mesomysis) intermedia (Czerniavsky, 1882)20082008
INVParamysis (Serrapalpisis) lacustris (Czerniavsky, 1882)19621962
INVParanais frici Hrabĕ, 194119701970
VERParanthias furcifer (Valenciennes, 1828)2011 20142011
INVParanthura japonica Richardson, 19092005 20072005
INVParasmittina alba Ramalho, Muricy & Taylor, 20112014 2014
INVParasmittina multiaviculata Souto, Ramalhosa & Canning-Clode, 20162016 2016
INVParasmittina egyptiaca (Waters, 1909)2016 2016
PPParasorites orbitolitoides Hofker, 19302016 2016
INVParatapes textilis (Gmelin, 1791)2004 2004
INV/parParatenuisentis ambiguus (Van Cleave, 1921)20012001
VERParexocoetus mento (Valenciennes, 1847)1955 1955
VERParupeneus forsskali (Fourmanoir & Guézé, 1976)2014 2014
INVParvocalanus crassirostris (Dahl F., 1894)2009 2009
PPPegidia lacunata McCulloch, 19772010 2010
VERPempheris rhomboidea Kossmann & Räuber, 18771983 1983
INVPenaeus aztecus Ives, 18912012 20182012
INVPenaeus hathor (Burkenroad, 1959)2012 2012
INVPenaeus monodon Fabricius, 17982011 2011
INVPenaeus japonicus Spence Bate, 18881972 19801972
INVPenaeus pulchricaudatus Stebbing, 19141961 19821961
INVPenaeus semisulcatus De Haan, 1844 [in De Haan, 1833–1850]2016 2016
PP/microPeridiniella catenata (Levander) Balech19871987
PP/microPeridiniella danica (Paulsen) Y.B.Okolodkov & J.D.Dodge1901 1901
PP/microPeridinium quadridentatum (F.Stein) Gert Hansen200520082005
INVPerinereis linea (Treadwell, 1936)2012 2012
PathogenPerkinsus chesapeaki McLaughlin, Tall, Shaheen, El Sayed & Faisal1992 19921992
PathogenPerkinsus olsenii R.J.G.Lester & G.H.G.Davis1983 1983
INVPerophora multiclathrata (Sluiter, 1904)1983 1983
INVPerophora viridis Verrill, 18711971 1971
INVPerophora japonica Oka, 19271982 1982
PPPetalonia binghamiseae (J.Agardh) K.L.Vinogradova1985 1985
INVPetricolaria pholadiformis (Lamarck, 1818)1896192718961985
VERPetroscirtes ancylodon Rüppell, 18352004 2004
INVPhallusia nigra Savigny, 18162008 2008
INVPhascolion convestitum Sluiter, 19021977 1977
INVPhascolosoma (Phascolosoma) scolops (Selenka & de Man, 1883)1975 1975
INVPhotis lamellifera Schellenberg, 19281990 1990
PathogenPhotobacterium damsela Love, Teebken-Fisher, Hose, Farmer III, Hickman & Fanning1992 1992
PPPhrix spatulata (E.Y.Dawson) M.J.Wynne,
M.Kamiya & J.A.West
1992 1992
INVPhyllorhiza punctata Lendenfeld, 18842005 20182005
VERPiaractus brachypomus (Cuvier, 1818)2013 2013
PPPikea californica Harvey1991 1991
INVPileolaria berkeleyana (Rioja, 1942)1977 20071977
INVPilumnopeus africanus (de Man, 1902)2013 2013
INVPilumnopeus vauquelini (Audouin, 1826)1963 1963
INVPilumnus minutus De Haan, 1835 [in De Haan, 1833–1850]2017 2017
INVPinctada fucata (A. Gould, 1850)2018 2018
INVPinctada radiata (Leach, 1814)1899 19981899
VERPinguipes brasilianus Cuvier, 18291990 1990
INV/parPiscicola pojmanskae Bielecki, 199420082008
INVPista unibranchia Day, 19631997 20051997
INVPlagusia squamosa (Herbst, 1790)1906 1906
VERPlaniliza haematocheila (Temminck & Schlegel, 1845)1972 19951972
PPPlanispirinella exigua (Brady, 1879)1910 1910
PPPlanogypsina acervalis (Brady, 1884)1909 1909
VERPlatycephalus indicus (Linnaeus, 1758)1978 1978
PPPlocamium secundatum (Kützing) Kützing1991 1991
INVPlocamopherus ocellatus Rüppell & Leuckart, 18282015 2015
VERPoecilopsetta beanii (Goode, 1881)1995 1995
INVPolyandrocarpa zorritensis (Van Name, 1931)1974 1974
INVPolycera hedgpethi Er. Marcus, 19641986 20011986
INVPolycerella emertoni A. E. Verrill, 18801964 19811964
INVPolycirrus twisti Potts, 19281983 1983
INVPolyclinum constellatum Savigny, 18162014 2014
INVPolydora colonia Moore, 19071983 20181983
INVPolydora triglanda Radashevsky & Hsieh, 20002014 2014
INVPolydora websteri Hartman in Loosanoff & Engle, 19432014 2014
PPPolyopes lancifolius (Harvey) Kawaguchi & Wang2008 2008
PPPolysiphonia paniculata Montagne1967 1967
PPPolysiphonia forfex Harvey2011 2011
PPPolysiphonia morrowii Harvey1975 19751997
PPPolysiphonia senticulosa Harvey1993 1993
VERPomacanthus imperator (Bloch, 1787)2016 2016
VERPomacanthus paru (Bloch, 1787)2015 2015
VERPomacanthus maculosus (Forsskål, 1775)1994 19942012
VERPomadasys stridens (Forsskål, 1775)1968 1968
INVPontogammarus robustoides (Sars, 1894)*19621962
PPPorphyra umbilicalis Kützing19891989
INVPortunus segnis (Forskål, 1775)1958 1958
INVPotamocorbula amurensis (Schrenck, 1862)2018 2018
INVPotamopyrgus antipodarum (Gray, 1843)*180118011887
INVPotamothrix moldaviensis Vejdovský & Mrázek, 190320082008
INVPotamothrix bavaricus (Oschmann, 1913)20152015
INVPotamothrix bedoti (Piguet, 1913)19151915
INVPotamothrix heuscheri (Bretscher, 1900)*19601960
INVPotamothrix vejdovskyi (Hrabĕ, 1941)*19671967
invPrionospio aluta Maciolek, 19851994 1994
INVPrionospio depauperata Imajima, 19902018 2018
INVPrionospio pulchra Imajima, 19901989 19891991
INVProasellus coxalis (Dollfus, 1892)20112011
INVProcambarus clarkii (Girard, 1852)*2000 2000
INVProkelisia marginata (Van Duzee, 1897)2011 2011
PP/microProrocentrum gracile Schütt1989 1989
INVProsphaerosyllis longipapillata
(Hartmann-Schröder, 1979)
1997 1997
VERProterorhinus nasalis (De Filippi, 1863)20202020
INVProtodorvillea biarticulata Day, 19631975 1975
INVProtoreaster nodosus (Linnaeus, 1758)1981 1981
INVPsammacoma gubernaculum (Hanley, 1844)2009 2009
PP/microPseudochattonella farcimen (Riisberg I.)199820011998
PP/microPseudochattonella verruculosa (Y.Hara & M.Chihara) S.Tanabe-Hosoi, D.Honda, S.Fukaya, Y.Inagaki & Y.Sako199820151998
INV/parPseudodactylogyrus anguillae (Yin & Sproston, 1948)198219851982
INV/parPseudodactylogyrus bini (Kikuchi, 1929)198519851997
INVPseudodiaptomus marinus Sato, 19132007 20102007
INVPseudonereis anomala Gravier, 18991969 1969
PP/microPseudo-nitzschia australis Frenguelli1995 19952000
PP/microPseudo-nitzschia multistriata (Takano) Takano1985 1985
INVPseudopolydora paucibranchiata (Okuda, 1937)1977 19821977
VERPteragogus trispilus Randall, 20131992 1992
VERPterois miles (Bennett, 1828)2009 2009
INVPtilohyale littoralis (Stimpson, 1853)2009 2009
INVPurpuradusta gracilis notata (Gill, 1858)1988 1988
INVPyrgulina pupaeformis (Souverbie, 1865)1995 1995
INVPyromaia tuberculata (Lockington, 1877)2016 2016
PPPyropia yezoensis (Ueda) M.S.Hwang & H.G.Choi1975 19841975
PPPyropia suborbiculata (Kjellman) J.E.Sutherland, H.G.Choi, M.S.Hwang & W.A.Nelson2010 20102014
INVPyrunculus fourierii (Audouin, 1826)1995 1995
INVRangia cuneata (G. B. Sowerby I, 1832)199720111997
INVRapana venosa (Valenciennes, 1846)1956 199719731956
VERRastrelliger kanagurta (Cuvier, 1816)2018 2018
INVRhinoclavis kochi (Philippi, 1848)1976 1976
INVRhithropanopeus harrisii (Gould, 1841)19361936195019941948
PP/microRhizosolenia calcar-avis Schultze2009 2009
INVRhopilema nomadica Galil, 19901995 1995
INVRingicula minuta H. Adams, 18722019 2019
INVRissoina bertholleti Issel, 18691985 1985
INVRuditapes philippinarum (Adams & Reeve, 1850)1973 19731980
PPRugulopteryx okamurae (E.Y.Dawson) I.K.Hwang, W.J.Lee & H.S.Kim2002 20152002
PPSaccharina japonica (J.E. Areschoug) C.E.Lane, C.Mayes, Druehl & G.W.Saunders1976 19801976
INVSaccostrea cuccullata (Born, 1778)2007 2007
INVSaccostrea glomerata (Gould, 1850)1984 1984
VERSalvelinus fontinalis (Mitchill, 1814)*1916 1916
PPSarconema filiforme (Sonder) Kylin1990 1990
PPSarconema scinaioides Børgesen1980 1980
PPSargassum muticum (Yendo) Fensholt1972 19721980
VERSargocentron rubrum (Forsskål, 1775)1943 1943
VERSaurida lessepsianus Russell, Golani & Tikochinski, 20151960 1960
PPScageliopsis patens Wollaston1989 1989
VERScarus ghobban Forsskål, 17752010 2010
VERScatophagus argus (Linnaeus, 1766)2007 2007
INVSchizoporella japonica Ortmann, 18901976 1976
INVSchizoporella pungens Canu & Bassler, 19282010 2010
VERSciaenops ocellatus (Linnaeus, 1766)2016 2016
INVScolelepis (Parascolelepis) gilchristi (Day, 1961)1977 1977
INVScolelepis korsuni Sikorski, 19941994 1994
INVScolionema suvaense (Agassiz & Mayer, 1899)1950 1950
VERScomberomorus commerson (Lacepède, 1800)2008 2008
INVScyllarus caparti Holthuis, 19521977 1977
PPScytosiphon dotyi M.J.Wynne1968 19911968
VERSebastes schlegelii Hilgendorf, 18802008 2008
INVSebastiscus marmoratus (Cuvier, 1829)2016 2016
INVSepioteuthis lessoniana Férussac [in Lesson], 18312009 2009
INVSeptifer cumingii Récluz, 18482005 2005
VERSiganus fuscescens (Houttuyn, 1782)2020 2020
VERSiganus virgatus (Valenciennes, 1835)1975 1975
VERSiganus luridus (Rüppell, 1829)1964 1964
VERSiganus rivulatus Forsskål & Niebuhr, 17751925 1925
PPSigmamiliolinella australis (Parr, 1932)2001 2001
VERSillago suezensis Golani, Fricke & Tikochinski, 20132009 2009
INVSinelobus vanhaareni Bamber, 2014200620102006
INVSinezona plicata (Hedley, 1899)2019 2019
INVSmaragdia souverbiana (Montrouzier in
Souverbie & Montrouzier, 1863)
1993 1993
INVSmittina nitidissima (Hincks, 1880)2014 2014
INVSmittoidea prolifica Osburn, 19521995 1995
PPSolieria filiformis (Kützing) P.W.Gabrielson1922 1922
PPSorites variabilis Lacroix, 19411996 1996
PPSpartina anglica C.E. Hubbard1924 1924
PPSpartina densiflora Brongn.1986 1986
PPSpartina patens (Aiton) Muhl.1986 1986
PPSpartina alterniflora Loisel1806 1806
PPSpermothamnion cymosum (Harvey) De Toni2010 2010
INVSphaeroma walkeri Stebbing, 19051977 201519772004
PPSphaerotrichia firma (E.S.Gepp) A.D.Zinova1981 1981
INVSphaerozius nitidus Stimpson, 18582013 2013
VERSphyraena chrysotaenia Klunzinger, 18841964 1964
VERSphyraena flavicauda Rüppell, 18382003 2003
INVSpirobranchus tetraceros (Schmarda, 1861)1970 1970
PPSpiroloculina angulata Cushman, 19171996 1996
PPSpiroloculina antillarum d’Orbigny, 18391911 1911
INVSpirorbis (Spirorbis) marioni Caullery & Mesnil, 18971974 19741977
INVSpondylus spinosus Schreibers, 17932001 2001
PPSpongoclonium caribaeum (Børgesen) M.J.Wynne1967 19671974
VERSpratelloides delicatulus (Bennett, 1832)2014 2014
VERStegastes variabilis (Castelnau, 1855)2014 2014
INVStenothoe georgiana Bynum & Fox, 19772010 20112010
VERStephanolepis diaspros Fraser-Brunner, 19401935 1935
INVSternodromia spinirostris (Miers, 1881)1969 1969
INVSticteulima lentiginosa (A. Adams, 1861)1995 1995
INVStomatella sp.2011 2011
INVStreblospio gynobranchiata Rice & Levin, 19982011 2011
INVStreblospio benedicti Webster, 18791982 1982
INVStyela plicata (Lesueur, 1823)1877 19891877
INVStyela canopus (Savigny, 1816)2006 2006
INVStyela clava Herdman, 188119682017196820052002
PPStypopodium schimperi (Kützing) M.Verlaque & Boudouresque1990 1990
INVSyllis hyllebergi (Licher, 1999)1972 1972
INVSyllis pectinans Haswell, 19201982 19822013
PPSymphyocladia marchantioides (Harvey)
1971 19711984
PPSymphyocladiella dendroidea (Montagne) D.Bustamante, B.Y.Won, S.C.Lindstrom & T.O.Cho1993 20051993
INVSymplegma rubra Monniot C., 19722014 2014
INVSymplegma brakenhielmi (Michaelsen, 1904)2003 2003
VERSynagrops japonicus (Döderlein, 1883)1987 1987
INVSynaptula reciprocans (Forsskål, 1775)1967 1967
VERSynchiropus sechellensis Regan, 19082014 2014
INVSynidotea laticauda Benedict, 18971975 1975
INVSyphonota geographica (A. Adams & Reeve, 1850)1999 1999
INVSyrnola fasciata Jickeli, 18821995 1995
INV/parTaeniastrotos sp.1993 1993
PP/microTakayama tasmanica de Salas, Bolch &
2008 2008
INVTelmatogeton japonicus Tokunaga, 1933196219621979
INVTenellia adspersa (Nordmann, 1845)2001 2001
VERTerapon theraps (Cuvier, 1829)2007 2007
INVTerebella ehrenbergi Gravier, 19061952 1952
INVTeredo bartschi Clapp, 19232003 20032007
INVThalamita gloriensis Crosnier, 19621977 1977
INVThalamita poissonii (Audouin, 1826)1969 1969
PP/microThalassiosira nordenskioeldii Cleve1967 1967
PP/microThalassiosira hendeyi Hasle & G.Fryxell1978 1978
PP/microThalassiosira tealata Takano1968 1968
PP/microThecadinium yashimaense S.Yoshimatsu,
S.Toriumi & J.D.Dodge
2002 2002
INVThelepus japonicus Marenzeller, 18842017 2017
INVTheora lubrica Gould, 18612001 20102001
INVTimarete punctata (Grube, 1859)2006 2006
INVTonicia atrata (G.B. Sowerby II, 1840)1978 1978
VERTorquigener flavimaculosus Hardy & Randall, 19832006 2006
INVTrachysalambria palaestinensis (Steinitz, 1932)1995 1995
INVTremoctopus gracilis (Souleyet, 1852) 1937 1937
INVTricellaria inopinata d’Hondt & Occhipinti
Ambrogi, 1985
1982 19961982
INVTriconia rufa (Boxshall & Böttger, 1987)2004 2004
INVTriconia umerus (Böttger-Schnack & Boxshall, 1990)2004 2004
INVTridentata marginata (Kirchenpauer, 1864)1980 19801990
VERTridentiger barbatus (Günther, 1861)2016 2016
PP/microTrieres mobiliensis (J.W.Bailey) Ashworth &
1983 1983
PP/microTrieres regia (M.Schultze) M.P.Ashworth & E.C.Theriot1989 1989
VERTrinectes maculatus (Bloch & Schneider, 1801)1984 1984
PP/microTripos arietinus (Cleve) F.Gómez1992 1992
PP/microTripos macroceros (Ehrenberg) F.Gómez1983 1983
INVTrochus erithreus Brocchi, 18211985 1985
INVTubastraea tagusensis Wells, 19822017 2017
INVTurbonilla edgarii (Melvill, 1896)1996 1996
VERTylerius spinosissimus (Regan, 1908)2004 2004
VERTylosurus crocodilus crocodilus (Péron & Lesueur, 1821)2003 2003
PPUlva australis Areschoug1984 19901984
PPUlva californica Wille2006 20062011
PPUlva gigantea (Kützing) Bliding2015 2015
PPUlva ohnoi M.Hiraoka & S.Shimada2011 20152011
PPUlvaria obscura (Kützing) P.Gayral ex C.Bliding1985 1985
PPUmbraulva dangeardii M.J.Wynne & G.Furnari2014 2014
PPUndaria pinnatifida (Harvey) Suringar1971 19751971
PPUndella hadai Balech2004 2004
VERUpeneus moluccensis (Bleeker, 1855)1947 1947
VERUpeneus pori Ben-Tuvia & Golani, 19892003 2003
INVUrocaridella pulchella Yokes & Galil, 20062018 2018
PPUronema marinum Womersley1989 1989
INVUrosalpinx cinerea (Say, 1822)1960 1960
INVVallicula multiformis Rankin, 19561998 1998
VERVanderhorstia mertensi Klausewitz, 19742019 2019
VERVariola louti (Forsskål, 1775)2018 2018
PPVaucheria longicaulis Hoppaugh2020 2020
INVViriola sp.[cf. bayani] Jousseaume, 18842016 2016
INVWatersipora aterrima (Ortmann, 1890)1983 1983
INVWatersipora subatra (Ortmann, 1890)1987 1987
INVWatersipora arcuata Banta, 19691990 19902013
PPWomersleyella setacea (Hollenberg) R.E.Norris1986 1986
INVXanthias lamarckii (H. Milne Edwards, 1834)2013 2013
INVXenostrobus securis (Lamarck, 1819)1991 20051991
INVYoldia limatula (Say, 1831)2019 2019
INVZafra savignyi (Moazzo, 1939)1995 1995
INVZafra selasphora (Melvill & Standen, 1901)1995 1995
VERZebrasoma flavescens (Bennett, 1828)2008 2008
VERZebrasoma xanthurum (Blyth, 1852)2015 2015
The Baltic Sea dataset encompasses 100 NIS introductions (including 6 parasites and 9 microalgae), 34 of which were introduced before 1970. The major proportion of the introductions since 1970 have been invertebrates (42 species, ~83%), followed by primary producers (5 species, ~10%), and vertebrates (4 species, ~8%). Invertebrates consist of a wide range of benthic crustaceans, as well as pelagic zooplanktonic taxa, whereas primary producers include both, phytoplankton, and phytobenthic species. Vertebrate species include Ponto-Caspian sturgeons and gobies, as well as cultured salmonids.
456 NIS are known from the North-East Atlantic (NEA), 372 of which have been detected since 1970 (81%). The Greater North Sea (ANS) hosts 260 NIS including parasites and pathogens (Figure 4b), 193 of which (74%) have been observed since 1970. The NIS biota is dominated by invertebrates (154 taxa = 59%) and primary producers (macroalgae, microalgae, pathogens) 88 taxa (34%). The proportion of vertebrates (fish) is low (18 taxa = 7%), and mostly related to freshwater NIS expanding their distribution into estuarine coastal waters.
The Celtic Seas (ACS) host 107 NIS including parasites and pathogens (Figure 4b), 72 of which (67%) have been detected since 1970. The vast majority (69 taxa = 64%) are invertebrates, followed by primary producers (35 taxa = 33%) while vertebrates are represented only by three freshwater fishes that have been observed in Irish estuarine waters.
The Bay of Biscay and Iberian Shelf (ABI) subregion hosts 250 NIS, 215 of which (86%) have been introduced since 1970. Most of them are invertebrates (180 taxa = 72%), followed by primary producers (68 taxa = 27%) and vertebrates (2 taxa = 1%).
The Macaronesia (AMA) hosts 121 species, 109 (90%) introduced since 1970. Invertebrates dominate (72 taxa = 59%), followed by primary producers (29 taxa = 24%) and vertebrates (20 taxa = 17%).
The Mediterranean NIS list includes 578 species (473 = 83% since 1970) dominated by invertebrates (59%) (Figure 4a). Primary producers follow with approximately 23% of species among which macroalgae and Rhodophyta prevail. Vertebrates (103 taxa = 18%) are dominated by Red Sea (Lessepsian) fishes. The contribution of NIS groups varies among the Mediterranean subregions (Figure 2c). Primary producers have their largest representation in MWE and MAD (31–32%), introduced as contaminants in shellfish consignments in the major shellfish culture areas of the northern Adriatic and the French coast. On the other hand, the percentage of vertebrates is higher in MAL where they mostly arrived through the Suez Canal, and in MIC which receives naturally dispersing fish from MAL than all other subregions.
The EU part of the Black Sea (Bulgaria and Romania) hosts only 38 validated NIS out of a total of more than 110 NIS reported for the whole Black Sea. These are mostly invertebrates (33 species) with crustacean and molluscan species dominating. Only 24 NIS have been reported since 1970 including two microalgae.
In addition to the 874 NIS in European waters, 57 NIS detected in one regional sea are native or cryptogenic in at least one other regional Sea (Supplementary Table S1). These include macroalgae (18 taxa), mollusks (13 taxa), crustaceans (11 taxa), cnidarian (5 taxa), polychaetes (5 taxa), tunicates (2 taxa), bryozoan (1 taxon), Fish (1 taxon), and microalgae (1 taxon). They have been transferred from the NEA to the MED and BLK Seas (more than 27 taxa), but also from the MED to the NEA (more than 22 taxa). Finally, six species have been transferred from the EU BLK waters to the BAL.
Species classified as NIS in a country but partly native or cryptogenic within the subregion/region of the country were not included in the analyses, with some examples provided in Table 3. In contrast, species native in one subregion, but NIS in another subregion within the same MSFD region were not listed in Table 2 but are considered as NIS at the subregional level (Supplementary Table S2). They are mostly widespread native or cryptogenic species in the MED and NEA that have been classified as NIS in Macaronesia.
The trend in new NIS introductions per 6 year assessment periods varies among groups and regional seas (Figure 3). The upward trend observed for invertebrates at the pan-European level is evident in the BAL, NEA, and MED Seas but not in the BLK Sea.
Overall, the rate of new NIS introductions (excluding parasites, pathogens, and microalgae) at the Pan-European level has increased at what appears to be a linear trend since 1970 from six to 21 NIS per year (Figure 4a). While evident in most regional seas, the increase also obscures large regional differences such as the steep increase from the early 2000s to 2017 in the Baltic Sea (Figure 4b) and a decreasing trend in the Black Sea (Figure 4b) and the Celtic Seas (Figure 4c). Comparison with the latest assessment period (2018–2020) shows a decline in the annual average rate of new NIS introductions compared to the preceding trends in many regional seas. Thus, while the annual rate of NIS in the North-East Atlantic steadily increased since 1970, although with subregional differences, reaching 11 new NIS per year in the 2012–2017 period, the latest assessment period (2018–2020) indicated a decline to an average of five NIS per year (Figure 4b). The annual rate of new NIS in the Greater North Sea (ANS) increased rapidly in the 1994–1999 period and maintained the upward trend in the last assessment period reaching six new NIS per year (Figure 4c). In the Bay of Biscay and Iberian Shelf (ABI), a steady upward trend was observed until 2005, followed by a sharp increase in the following periods, reaching seven new NIS per year in the 2012–2017 period. A similar pattern to that of ABI was observed in Macaronesia where the annual rate reached five NIS/per year in the 2012–2017 period. The highest number of new NIS introductions in the Celtic Seas occurred in the assessment period 1994–2005 with two new NIS per year. A declining trend was observed in the last assessment periods. Only five invertebrates were detected in the 2012–2017 period, and none since 2017.
All analyses in the Mediterranean Sea are based on 460 NIS taxa observed for the first time since 1970. On an annual basis, the number of newly introduced NIS has increased in the Mediterranean since the late 1990′s reaching 14 species per year in the period 2012–2017 (Figure 4b). This increasing trend is also observed at a subregional level for all regions but the MWE. Specifically, the annual new NIS rate calculated in the assessment period (2012–2017) reached 11 new NIS per year in the MIC, followed by nine in the MAL, seven in the MWE and six in the MAD (Figure 4d). In the MWE, the annual rate of NIS introductions fluctuates between two and seven species per year without any pronounced peaks or temporal trends. In contrast, a slight leveling off in the introductions rate appears in the MAD, while the rate of new NIS introductions presents a steeper increase in the MAL and MIC after the mid-2000s.
The rate of introductions in the BLK peaked in the 1994–2006 period reaching one new NIS per year but dropped in the following periods (Figure 4b). As many as six species (18%) have expanded the geographic range from neighboring areas surrounding the Black Sea where they first invaded, while the presence of two NIS namely the oysters Crassostrea virginica and Magallana gigas is attributed to escape from confinement (oyster culture facilities).

4. Discussion

With the current work, we aimed at establishing an updated status of NIS in European waters to provide a robust baseline for understanding trends in new NIS arrivals. The presented analyses documented an increasing trend in the annual rate of new NIS at all spatial levels until 2017 while highlighting some major regional differences both in the composition of xenodiversity and the temporal evolution of new NIS introductions at the subregional level, that can prove useful in further steps of setting thresholds for NIS trends indicators. Our findings are discussed in the context of spatial, temporal, species-specific and effort-related sources of uncertainty (Figure 5), which are primarily epistemic in nature (sensu [43,44]) i.e., they relate to measurement or systematic error, be it in species taxonomy, identification, and origin, in the spatial aspects of inventories or the temporal uncertainties associated with trends estimation. Subjective judgment may introduce additional uncertainty in determining species to include/exclude from management actions, such as cryptogenic species or functional groups addressed with different policy instruments. Finally, we provided an explicit account of partly native species in different management units, helping to resolve linguistic uncertainties stemming from a context-dependent definition of the terms alien/native.

4.1. Validation of European NIS: A Challenging and Dynamic Task

One of the main challenges in establishing a robust and accurate baseline is addressing taxonomic or biogeographic uncertainties and incorporating new taxonomic information. To maintain a conservative viewpoint and avoid potential false positives, the authors agreed to exclude species that have raised uncertainties regarding (i) the known existence of cryptic species, (ii) recent taxonomic revisions, (iii) suspicions of possible errors for taxa belonging to species complex, and/or (iv) species that are possibly non-native but only recently described and thus requiring further clarification about their status. Issues arising from cryptic species, taxonomic revision, and occurrence of species complexes were noticed in the NEA for the ascidians Botrylloides schlosseri, Ciona intestinalis, and the mussels Mytilus galloprovincialis and Mytilus trossulus.
Botrylloides schlosseri is an example of the problems associated with the identification of cryptic species complexes, which are common among widely distributed marine taxa [45]. An extensive study by Bock et al. [46] showed that several cryptic species of B. schlosseri coexist at a regional scale in northwestern Europe. Some are probably native (e.g., clade E in Brittany, France) while others are likely to be introduced, considering their near-global distribution (e.g., clade A in Brittany, France). The specimens of B. schlosseri, reported in the North-East Atlantic, could thus be either NIS or native species. Thus, overall, it seems more reasonable to assign B. schlosseri a cryptogenic status.
In the case of Ciona intestinalis, uncertainties stem from a recent extensive taxonomic revision [47]. Based on a series of morphological and molecular investigations (references in 47), this species name was shown to bring together two distinct species, namely Ciona intestinalis and Ciona robusta, which had previously been described as two distinct species but unfortunately synonymized in 1985. Until a recent taxonomic revision, C. robusta was known as C. intestinalis type A and C. intestinalis as C. intestinalis type B although the type was not always reported. Furthermore, since the taxonomic revision was announced in 2017, the use of the correct species name is questionable for our dataset ending in 2020. C. robusta, native to Asia, is the only Ciona species introduced, so far, to the North-East Atlantic (in the early 2000s) [48,49]. We, therefore, excluded records of C. intestinalis and retained only records of C. robusta or C. intestinalis type A, as the use of these names refers to the Pacific-origin species.
The situation is even more complicated with the Mytilus edulis species complex, which obscures three European accepted species M. edulis, M. galloprovincialis and M. trossulus that still hybridize and exchange genes at contact zones. In our list, we have two species reported as introduced in the North-East Atlantic, for which reports are questionable: M.e galloprovincialis and M. trossulus. The use of the species name M. galloprovincialis is insufficient to determine native vs. introduced status, as it covers two distinct lineages, one present in the Mediterranean Sea, and the other in the Atlantic [50]. As with C. intestinalis prior to its taxonomic revision, the name M. galloprovincialis does not allow us to determine the native or introduced status of specimens reported from the North-East Atlantic. In addition, the natural presence of the Atlantic lineage as enclosed population patches in Brittany, Wales, Scotland, and Northern Ireland is not always recognized by some specialists and is debated. In the case of M. trossulus, identification has most often been established using barcoding or metabarcoding based on the COI mitochondrial marker. However, in the absence of details regarding the reference sequence that was used for the taxonomic assignment, we face another problem here. Some of the reference data available in public databases are indeed from specimens collected in the Baltic Sea, where the mitochondrial genome of M. trossulus has been extensively introgressed (i.e., replaced) by that of M. edulis, which may lead to a false taxonomic assignment of a M. edulis specimen to M. trossulus [51]. In addition, recent work has shown that M. edulis carries a transmissible cancer of M. trossulus origin. Thus, molecular-based identification may lead to the assignment of M. trossulus or edulis-trossulus hybrids for M. edulis specimens with this cancer [52,53]. The so-called “Baltic Mytilus trossulus” actually differs distinctly in morphology, ecology and genetic characters from M. trossulus, i.e., a species described from the NE Pacific [54]. To resolve this, Mytilus edulis balthicus by Gittenberger and Gittenberger, 2021, has recently been described. In addition, to further the nomenclatorial stability within the M. edulis complex, the locus typicus restrictus of the nominal taxon M. edulis has been restricted to the North Sea off the Dutch coast [54].
The improvement of molecular methods in ecological studies has helped to shed some light on species’ origins and their actual distribution, (see for instance the case of Tritia neritea detailed in the next Section). However, at the same time, this may give rise to some controversies until further studies finally provide unequivocal confirmation of status with more data. This is the case, for example, of the oyster Ostrea stentina, which was recently found to encompass two different genotypes, one of them belonging to the newly described Ostrea neostentina with type locality in Hong Kong [55]. A new distribution map of this genus has thus been constructed, with O. stentina present in both the MED and NEA regions, and O. neostentina only in the MED. New studies are taking place to confirm the native range, but, so far, regarding the present knowledge of historical records and taxonomical studies, the population of O. stentina present in the ABI subregion is considered introduced.
In addition, systematics is a dynamic field of research, as novel species are continuously being described; some of them possibly being novel introduced species. However, in the absence of further verification regarding their status, we did not include some of these species in our list. A case in point is that of the spaghetti worm Terebella banksyi nov. sp [56] newly described following its collection in 2017 in Arcachon Bay and found in farms or reefs of the Pacific oyster Magallana gigas. Similar uncertainty is occurring for the newly described colonial tunicate Didemnum pseudovexillum nov. sp [57], distinctive from the well-known invader D. vexillum by morphological traits and genetic characteristics and found only in marinas in the Celtic Seas (Brittany, France) and NW Mediterranean Sea (Spain). Considering the habitats (farms, marinas) and extensive range of D. pseudovexillum nov., it is likely that it had been introduced. However, further clarification would be needed to ascertain its introduced or cryptogenic status.
We included in the list of accepted species that arose following hybridization between a NIS and a native species. Hybridization between native and introduced species is very common in plants [58,59]. It has also been documented in marine species although being still poorly examined, and yet an important issue to consider for marine NIS management [6]. In coastal systems, this process is well-illustrated by cordgrass species from the Spartina genus [60,61]. For instance, S. alterniflora hybridized with the native species S. maritima after its introduction in the United Kingdom. This hybridization gave rise to S. townsendii, a sterile species, which then gave rise through polyploidization to S. anglica. The latter species is highly successful, displacing the native S. maritima, and is present in most of the ANS and locally in the western BAL. Thus, S. anglica is not per se introduced but is included in our list, because it would have never existed without the introduction of S. alterniflora in Europe.
Another cordgrass species, Spartina versicolor Fabre, has also a controversial taxonomic status. Although it was recorded as NIS in several European countries in the 19th and 20th centuries, it was considered synonymous with Spartina patens, due to morphological similarities [62,63] sampled several populations of S. versicolor in the Mediterranean, Atlantic, and North Africa saltmarshes and conducted cytogenetic and molecular analysis (microsatellite, nuclear and chloroplast DNA sequences) and compared it to North American Spartina species. Their results supported the hypothesis that all European and African populations of S. versicolor are, in fact, North American S. patens, introduced before or at the beginning of the nineteenth century. Due to potential hybridization within Spartina species, further investigations are needed to clarify any potential hybridizations between introduced species with the native ones (e.g., S. maritima).

4.2. Issues with Assessing the Spatial Distribution of NIS in Europe’s Seas

The NIS data-gathering process is not standardized (there is no consistent methodology) among EU Member States, which is a drawback and likely to generate bias and uncertainty in the assessment itself. In addition, biases may arise from the lack of dedicated surveillance programs. Not only studies focused on NIS introduction hot spots, such as ports and marinas or aquaculture facilities, but also the increment of monitoring programs to give responses to other MSFD descriptors increased the probability of finding newly introduced NIS during the surveys. However, it must be highlighted that several new records are introductions that most probably either went unnoticed in previous surveys or from areas that were never previously investigated. Monitoring programs are also not equally implemented in all subregions, and only a few have specifically focused on NIS and cryptogenic species detection [14].
Therefore, data need to be updated continuously from other monitoring programs or scientific literature reporting NIS. For example, in the NEA region, subregions such as ANS or ACS have historically received more attention than ABI [64]. In several countries such as Spain, Portugal, and Denmark, there were no baseline studies for NIS until very recently and the list included in the last assessment period (2012–2017), can therefore be considered as a baseline for some countries.
Boundaries between sub-regions established for MSFD reports are also challenging. In particular, the ABI subregion boundaries, as the boundaries between ANS and ACS, very often raise questions when establishing the status of some species because the natural borders between water masses are not static at these human-established borders (Figure 1). The same holds for the MWE subregion. Its western limit finishes a few kilometers after the strait of Gibraltar making it difficult to establish proper frontiers between Mediterranean and Atlantic waters since the Mediterranean shows a high influence even until central Atlantic waters [65]. In this sense in the southern extension of the ABI subregion, being highly influenced by Mediterranean waters, some species whose native range extends in both NEA and MED regions can be found, giving them the category of partly native species in a subregion, but being NIS in a country of this same subregion (Table 3) or in another subregion of the same region. This is the case, for example, of the gastropod Cymbium olla, whose native range includes Algarve (southern Portugal) and the Gulf of Cadiz (southern Spain—Atlantic coast), which are part of the ABI subregion, but also Cadiz in the Alboran Sea site, which is in the MWE subregion. Therefore, Cymbium olla, which is partly native in the MWE subregion even in some other localities in the MWE, might be locally classified as NIS [66].
Species distribution and their possible expansion, are never contained within any human delineation of marine borders, making it difficult to categorize their status when it comes to classification at any bordering level (subregion, region, or Pan-European). This issue is particularly important for species spreading gradually, which might be considered either as a natural expansion or introduced by human activities. For example, the nassariid gastropod Tritia neritea’s native range includes the Mediterranean and the Black Sea, as well as all around the Iberian Peninsula (Hidalgo [67] as Cyclops neriteum), but since the 1970s, this gastropod has been extending its range along the coast of Frances since its first record in 1976 in Arcachon Bay [68]. Its presence almost exclusively in oyster farming areas and the genetic characteristics of the French populations (e.g., admixture of lineages found in different locations of the Mediterranean Sea that indicated multiple introductions [69]) finally concur to report this nassariid gastropod as a NIS, probably introduced by oyster cultures in France [70]. Therefore, it is considered partly native to the ABI subregion because of its native range in Portugal and Spain, and its later introduction in France (Table 3). Some cases such as Tritia neritea, exemplify the difficulty of sometimes categorizing species as either NIS, cryptogenic or native because of their life history, migratory and demographic history, influenced by paleoclimatic events in a longer time scale and more recently by human activities [69,71]. These processes determine the species’ contemporary distribution, showing a patched map of native and introduced localities, even at local small scales [72].
Another example of a partly native species is that of the amphipod Ericthonius didymus (Krapp-Schickel, 2013), which was described in the Adriatic Sea from the Venice Lagoon (Italy). This recent description was rapidly followed by new records in Europe both in the Mediterranean and the Atlantic between 2013 and 2017 [73]. These observations, some of which date back to the year of description of the species, do not allow an unequivocal designation of the species as non-indigenous in the Bay of Biscay. However, the species is considered NIS in the ANS and the AMA, due to its presence in anthropogenically stressed sites, such as harbors/marinas and shellfish grounds [73].

4.3. Trends Indicator

Across all taxonomic groups, the rate of new NIS introductions in EU waters has increased gradually since 1970 and reached an average of 21 NIS per year in the period 2012–2017. The same upward trend was noticed for the Baltic, North-East Atlantic, and the Mediterranean Sea, but was more evident in the Mediterranean and Baltic Seas. In contrast, a decreasing trend was seen in the Black Sea with only one new species detected in the last assessment periods (0.2–0.3 NIS per year). Low figures noticed in the periods of 1988–1993 and 2000–2005 are likely an artifact of varying monitoring and reporting efforts between the regions over these periods.
The high rate of annual Introductions from 2000–2005 was very likely associated with a growing research interest in NIS, rather than discrete episodic events leading to high levels of new introductions during these years. Indeed, the development of several dedicated projects (AquaNIS, DAISIE, EASIN) produced outputs with updates on the list of NIS.
The decreased annual rate of new NIS introductions in the period 2018–2020 at almost all geographic levels examined has recently been attributed to time lags in reporting [74] rather than a result of NIS intervention programs. Also, there are fewer sampling years in this last interval analyzed, which might entail larger variability in the annual rate. This provisional reduction of new NIS registered is furthermore not likely to be associated with the implementation of measures since no new programs of measures have been implemented yet (e.g., only three marine NIS, the fish Plotosus lineatus, the seaweed Rugulopteryx okamurae, and the crab Eriocheir sinensis (only partly marine), are in the EU list of Invasive Alien Species of Union concern) and the implementation of the Ballast Water Management Convention at the European level is still in progress [75]. The only exception is the Council Regulation (EC) No 708/2007 of 11 June 2007 concerning the use of alien and locally absent species in aquaculture that may have decreased the risk of novel species introduced for cultivation purposes, although not preventing transfer within each EU country’s borders. A decrease in new NIS records in the last assessment period (2018–2020) for most regions might furthermore be explained by the homogeneity of marine NIS fauna since more and more species previously found exclusively in one of the countries are now found in more countries. Probably many species are expanding naturally from previously invaded countries.
The present upward trend in new NIS introductions to the Baltic Sea contradicts the previous D2C1 assessment, which indicated that the trend was decreasing since 2011 [76]. The discrepancy is very likely due to updated NIS records from several countries around the Baltic Sea. The latest assessment period in the present study covered only three years (2018–2020), but already five new NIS were recorded from the EU marine waters of the Baltic Sea during this time, suggesting that the ultimate HELCOM goal of zero new NIS introductions will not be reached, even though the rate of new NIS introductions has dropped to less than two new NIS per year. Overall, the current Baltic Sea analysis indicated that the number of new introductions has had a steep increase from the early 2000s to 2017. The increase may be due to growing scientific interest and promotion of citizen science projects [77], but it is evident that anthropogenic pressure through intensified shipping has steadily increased toward the marine environment of the Baltic Sea [78].
The NEA region encompasses several ecoregions, 4 sub-regions, and 10 different countries, making this region a very complex one for analyzing trends because of the heterogeneity in surveys and ecosystems. It is thus not surprising that quite a large number of species are reported as NIS within the region, and subregions (Figure 4b,c). Altogether the number of novel NIS has always been increasing, at least for invertebrates that are the most numerous NIS in this region (Figure 3). This is likely attributed to the continued increased maritime traffic in the region. Indeed, overall shipping density increased across the North-East Atlantic by 33.6% between 2013 and 2017 [79].
In comparison to the previous assessment [3,15,32], this work does not consider data from the UK waters. This leads to differences not only in the total number of NIS but also in the trends indicator as first detection dates may be years earlier in neighboring non-EU countries.
An earlier assessment (over the period of 2003–2014) of NIS in the ANS, ACS, and the ABI subregions showed that the number of newly recorded NIS varied by year and region showing a relatively constant linear increase in the ANS only, but not so in the ACS and ABI [80]. In this study, an increasing trend was observed in all subregions but the ACS. The high number of NIS in the ABI in the 2012–2017 period (7 NIS/year) is partly attributed to intensive studies in port areas and marinas [81,82,83] in the framework of the implementation of the MSFD descriptor 2 or research projects dedicated to NIS surveys. Furthermore, the increase of studies based on genetic analyses within this last decade has helped to rapidly and accurately detect newly introduced species reassess some species that have been misidentified, and elaborate an updated checklist of NIS [84,85,86]. In addition to traditional genetic approaches, in recent years metabarcoding of environmental DNA had been proposed and is increasingly used as a new tool to improve NIS detection [87]. The approach is promising and effective although it needs to be used cautiously to avoid both false negatives (i.e., present, but undetected NIS) and false positives (i.e., NIS erroneously detected) [51]. NIS detection by these methods requires fit-to-purpose protocols and should not be based on molecular data obtained for general biodiversity assessments [88]. Either way, the data show that the increase seems to be stabilizing, indicating that it is a good time to set the baseline.
The increasing trend in introductions in ANS, which culminated in the 2012–2017 period with six NIS per year, appears to be slowing down in the last assessment period (2018–2020) with four new NIS per year, although future publications are expected to bring to light more NIS. During the period 2018–2020, in France, the number of records increased. However, this is the only French subregion with such an increase, thanks to dedicated surveys programs carried out in the Normandy region [86]; these reports are not new either for France or for ANS [89] (and references therein), suggesting a decrease of new species but an important dispersal between subregions.
In the ACS, the decrease is even more pronounced than in the ANS, with no novel NIS reported after 2017. As for the ANS, the difference from the previous assessment can be partly attributed to the geographic areas involved. In the previous assessment [76] the NIS of the United Kingdom in ACS were included in the analysis. Moreover, pathogens were also included. Additionally, in the Western English Channel (French and UK coastline), a research project (Interreg Marinexus project) dedicated to rapid assessment surveys of NIS in marinas, well-known introduction hotspots, was carried out over 2010–2017 [78], and provided novel reports for European waters (e.g., the ascidian Asterocarpa humilis [90]).
The AMA NIS list presented here represents an updated version of the list reported by Castro et al. [29] following similar criteria. As opposed to the current study, species that underwent tropicalization processes (see 29, 41) were considered one of the criteria for NIS attributes in Castro et al. [29] inventory. Most changes were made on macroalgae records for the Azores as more information on records, taxonomy, and distributional updates have been gathered and led to some changes. In addition, a few new records have been added as [29] included records only until 2020 whereas the present account includes records reported until summer 2022.
Comparisons with the full NIS inventory of the MED are somewhat hampered by the geographic coverage of the current study, which is limited to the EU waters of the Mediterranean (plus Albania and Montenegro). As a result, total numbers of new NIS, as well as annual introduction rates, appear to be reduced in comparison to, e.g., [30], especially for the eastern Mediterranean, as primary Lessepsian introductions restricted to the Levantine were outside the spatial scope of this study. Indicatively, the whole Mediterranean Sea hosts upward of 1000 validated NIS, 786 of which are in the MAL [12,23,91], compared with the 579 NIS present in the EU parts of these waters. As such, it is not surprising that the annual introduction rate in the central Mediterranean in the 2012–2017 period exceeds that of the eastern Mediterranean, as the accelerated sea warming rates favor the spread of Indo-Pacific species already present in the Levantine [92]. On the other hand, the reduction in Transport-Contaminant species [76], which are more prevalent in the Adriatic and the western Mediterranean, may have contributed to the observed leveling off or decreasing NIS trends in these two subregions. For the Mediterranean Sea as a whole, there appear to be two “stepwise” increases in new NIS introductions, the first one in the late 1990′s, mostly driven by introductions in the MAL and likely related to sea surface warming [30,93], and the second in the 2012–2017 period. This last peak could partly reflect intensified research efforts, which the whole basin has undoubtedly experienced in the last decade [94] as already suggested for other regions and subregions of the NEA, and in line with comments by Bailey et al. [31]. In Slovenia, for example, the number of detected NIS has increased from 17 in 2012 to 57 in 2021, which is due to increased targeted research, mainly founded by the Ministry of Agriculture, Forestry and Food for the implementation of D2 in the country [95]. It also coincides with a sharp increase in the introduction rate of fouling species, notably in marinas and on leisure boats, at least in their detection and reporting [96,97]. Hence it is difficult to really evaluate the significance of these trends without considering a measure of “effort”, which again starkly exemplifies the need for standardized monitoring for any assessments to be meaningful.
Some of the earlier invading NIS in the BLK such as the blue crab Callinectes sapidus (Rathbun, 1896) appear to be established and spreading in the area over the years. Callinectes sapidus was first found on the Bulgarian coast of the Black Sea in 1967 [98], most likely transferred in ballast water but could have been spreading via the Marmara Sea from an invasive population in the northern Aegean. Six new records of the blue crab have been documented near the Bulgarian Black Sea coast since 2010. This is evidence of a recent expansion of the species in this part of the Black Sea. This expansion could be explained by the existence of an established population in the area and is confirmed by the capturing of an egg-bearing female in Varna Bay in 2005 [99]. It is anticipated that in the face of climate change the number of NIS in the EU areas of the BLK will increase in the near future due to the spreading (Unaided pathway) of NIS from the North Aegean Sea that has already invaded the BLK via the Sea of Marmara such as the marbled pine foot Siganus rivulatus [100,101]. Moreover, NIS recently introduced via vessels in the northeastern and southern Black Sea could spread unaided in the study area [102,103]. Such is the case of the polychaetes Laonome xeprovala that spread in the Danube Delta–Black Sea Ecosystem and Marenzelleria neglecta that was detected in 2021 in the same area [103].

4.4. Uncertainties in Trends

Uncertainties in trends first rely on the uncertainty of the first date of the report (if not consistent across periods). The true introduction year of NIS may be different from the detection year. As an example, the Terebellid polychaete Marphysa victori was detected in 2016 and described in 2017 from French waters in the Arcachon Bay, with doubts already surrounding its true origin due to its presence in and close to oyster farms where Magallana gigas is cultivated [104]. This possibility was verified several years later. Marphysa victori is native to the Northwest Pacific [105], and it has undoubtedly been introduced as a contaminant with oyster transfers. However, it remains unproven if its introduction is a consequence of oyster importation from Japan. Between 1971 and 1975, about 1200 t of Magallana gigas spat collected from Sendai Bay (Japan) were introduced into Arcachon Bay. Marphysa victori has a substantial economic value as bait and is widely collected by recreational and professional fishermen. The number of worms collected in the lagoon (13 companies) could reach 1 million per year [104]. Reaching such densities within a year would be impossible. Thus 1975 was set as the most plausible year of its introduction.
Other examples include Mollusca species observations in EU waters around 80 years after their first detection in neighboring non-EU waters. Such are the cases of the gastropod Berthellina citrina (Rüppell & Leuckart, 1828), which was first reported in the MED from the Gaza Strip in 1940 [106], but only in 2019 in EU Mediterranean waters: Cyprus [107] or of the bivalve Gafrarium savignyi (Jonas, 1846) with a first Mediterranean record in 1905 from Egypt [108] but an EU record in 2005 from Cyprus [109].
Various policy measures relevant to the Baltic Sea countries can result in uncertainties regarding the emergent reports of new NIS introductions. Trend analyses on new NIS introductions to the Baltic Sea, such as [22,27,110] may differ mainly due to the applied assessment principles, e.g., area of interest, and species included in the analyses. Baltic Sea delineation determined according to the EU MSFD differs from HELCOM delineation, and this often leads to NIS being reported, for example, from the Kattegat area, which is BAL according to the HELCOM delineation, but at the same time a part of the ANS according to the EU MSFD delineation. In addition, Russian coastal waters outside of St. Petersburg and Kaliningrad are obviously part of the Baltic Sea but are not included in assessments that refer to the marine waters of the EU.
Even more, pronounced discrepancies may be observed with pan-Mediterranean assessments due to the exclusion of non-EU Mediterranean countries in this study (see above). Regardless of administrative boundaries for EU policies, it is crucial that the marine environment is managed with sufficient harmonization between regional policies. Toward that end, the Contracting Parties to the Barcelona Convention—21 Mediterranean countries and the European Union—have recently developed and adopted the Integrated Monitoring and Assessment Programme for the Mediterranean region (IMAP) [111]. Within its framework and in accordance with the MSFD [9], GES for NIS in the Mediterranean was defined as the minimization of the introduction and spread of NIS linked to human activities, in particular for potential IAS, with the reduction in human-mediated introductions as the proposed State Target [112], a target that clearly needs to be further refined but seems far from achieved based on our latest data.

4.5. Threshold Values

Qualitative GES assessments to date have been based on directional trends and, despite ongoing efforts [110], threshold values for the NIS trend indicator have not been set yet and neither have more specific recommendations been made for the magnitude of this reduction or the number of reporting cycles that will define the reference conditions [113].
Waiting for a value of the percentage reduction to be established at a European level, as suggested by [14], the French decree relating to the definition of GES states that GES is achieved if there is a significant decrease in the number of new NIS over two cycles at minimum. As visible in this work, the number of new NIS increased in all French marine subregions during the previous cycle (2012–2017), and the goal has therefore not been reached to date.
The identification and comprehension of impact thresholds on ABI marine native communities is required. ABI countries must collaborate more closely to implement common methodologies for MSFD implementation, particularly regarding non-indigenous species (D2) [114]. Furthermore, good coordination is required for the creation of an effective alert system. It is worth mentioning the risk-based approaches to good environmental status (RAGES) project, which attempted to establish reproducible, transparent, and standardized risk management decision procedures based on international best practices. The increase in the number of new NIS introductions in the period 2006–2017 seems to be stabilizing, indicating that it is a good time to set the baseline. This decrease in new NIS records might be explained by a biotic homogenization of the ABI marine NIS fauna since more and more species previously found exclusively in one of the countries are now found in all three ABI countries. Probably many species are expanding naturally from previously invaded countries.
In the Mediterranean Sea, preliminary analyses [12] indicated that threshold values should be established separately for each subregion and should be sought by examining the data of the last two decades, if not an even more recent period. Further work by Galanidi and Zenetos [30], based on breakpoint analysis of 1970–2017 NIS data, corroborated the validity of a subregional approach, demonstrating different temporal breakpoints in the rate of NIS introductions per subregion, ranging from 1997 in the MAL, to 2000 in the MAD, 2003 in the MWE and 2012 in the MIC. They suggest that the mean introduction rate of these periods can be used to define threshold values but stress that GES target refinement and percentage reduction cannot proceed without careful consideration of management objectives and pathway pressure, as also pointed out in Tsiamis et al. [14].
Trends in the arrival of new NIS is a core indicator of the Baltic Marine Environment Protection Commission (Helsinki Convention, HELCOM), and the primary criterion D2C1 was assessed for the first time for a six-year assessment period (2011–2016) in 2018 [10]. The report listed new NIS and cryptogenic species for BAL over the assessment period. Contracting Parties of HELCOM have set a precautionary threshold to assess GES in relation to NIS. Zero new NIS introductions through anthropogenic activities to the Baltic Sea per six-year assessment period has been defined as the GES for NIS [10], and therefore one or more introductions to BAL would result in GES not being reached. Furthermore, it has been argued whether a reduction in new NIS introductions could be set as an intermediate objective if the goal of no new introductions cannot be reached. Even though a proportional reduction of new NIS introductions between the assessment periods would indicate temporary improvement of GES, the “zero tolerance policy” was chosen as the GES threshold to the BAL, because it is pragmatic, independent of earlier assessment periods, applicable even with uncertainties in relation to taxonomy and introduction pathways, and efficiently reflecting management measures [10,110].

4.6. Concluding Remarks—The Way forward

Considering how dynamic biological invasions are, NIS inventories should be curated regularly, especially when used to inform policy, in order to minimize errors and avoid over- or under-estimating the state of invasions in a region [44]. While the validation process in this work explicitly addressed many of the taxonomic and spatial components of uncertainty in the EU NIS baseline, other issues remain unresolved, among which the lack of standardized monitoring needs to be urgently rectified both for the meaningful interpretation of results and for the refinement of the relevant indicators.
Regional and sub-regional analyses revealed that there are relatively strong variations in the number of new NIS introductions between the European seas, as well as among the subregions within the same region. Hence, it is natural that GES threshold values for the primary criterion D2C1 are discussed and decided under regional cooperation, as some regions have preferable conditions for a wider variety of species and thus tend to suffer from a higher number of introductions. In addition, NIS pathways are region-specific (e.g., the Suez Canal in the MED, shipping in the NEA). Shipping was found to be a likely vector for over half of NIS in European waters both through biofouling and ballast discharges [2], while biofouling, particularly of recreational vessels, appears to be an important driver for the homogenization of the alien biota in the Mediterranean. As such, a more detailed focus on quantitative measures of pathway pressure would help better elucidate the observed NIS patterns, inform target setting and evaluate GES achievement in relation to management. Considering that currently only aquaculture-related introductions are addressed with EU-wide legislation and that the BWMC is not expected to be fully implemented until 2024 at the earliest, expectations for percentage reduction should have a realistic temporal horizon and, if possible, promote management implementation for the remaining major introduction pathways. More specific national or local measures may be put in place to protect sectors or sensitive habitats, e.g., see [115] for additional measures related to shellfish culture in the Wadden Sea), pathways of species introductions however operate globally and should be managed at appropriate scales.

Supplementary Materials

The following supporting information can be downloaded at:, Table S1: Partly native or cryptogenic (CRY) species in European seas; Table S2: Species native/cryptogenic in one subregion, but NIS in another subregion.

Author Contributions

A.Z. and O.O.: conceptualization, review, and data collection. All authors: providing and validating national data, contribution with taxonomic expertise, interpretation of data. A.Z., O.O., M.G.: data analysis, writing the first draft of the manuscript. F.V. made significant contributions to early drafts of the manuscript. All authors wrote, revised, and contributed to the editing of the final manuscript. All authors have read and agreed to the published version of the manuscript.


A.Z. and O.O. were partially funded by the European Environment Agency, through ETC/ICM 2021. The authors from the National Institute of Biology (Slovenia) acknowledge the financial support of the Slovenian Research Agency (Research Core Funding No. P1-0237) and of the Ministry of Agriculture, Forestry and Food. F.V. is supported by the CNRS Institute for Ecology and Environment. This work benefited from results obtained during surveys carried out in the Interreg IVa Marinexus programme and the Aquanis2.