Indicator Specification

Trends in Marine Alien Species (MAS)

Indicator Specification
  Indicator codes: MAR 002
Published 02 Dec 2013 Last modified 11 Sep 2015
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The indicator for the marine and estuarine species represents the cumulative number (i.e. the sum) of primary producers (plants), invertebrate and vertebrate alien species that have been recorded in European waters since 1950

Assessment versions

Published (reviewed and quality assured)
  • No published assessments


Justification for indicator selection

Biological invasions are widely perceived as one of the main threats to biological diversity next to habitat destruction.   Of particular importance are the Invasive species namely those introduced alien species that establish themselves, spread rapidly and can threaten biological diversity in various ways, from reducing genetic variation and eroding gene pools, through the extinction of endemic species, and by altering habitat and ecosystem functioning (Hulme, 2007).
Invasive alien species have not been taken into enough consideration concerning the European Water Framework Directive (WFD) the Marine Strategy Framework Directive (MSFD) and other European directives until recently (Cardoso & Free, 2008; Olenin et al, 2007).
A factor determining good ecological quality and functioning of the ecosystem is high biodiversity. Intruding alien species can greatly influence these factors. A species such as the colonial seasquirt Didemnum vexillum could put great stress on the biodiversity in an area by covering many square kilometres of sea floor and overgrowing other indigenous species. Alien species can also hamper functions of water bodies that are important for humans, including shipping, fisheries, aquaculture production, recreation, public health, tourism
The ecological impacts of invasions are often inferred from distribution data under the assumption that the more abundant the alien species, the more severe the impact (Vila et al, 2010). There have been more than 1300 marine species introduced in European Seas (Katsanevakis et al., 2013) and the impact of them on local ecosystems has been studied for less than 100 of them.
In the lack of data on impacts (as well as trends) of most of the introduced species in European Seas, the trends in NIS – Non Indigenous species  (all introduced species) is used as a proxy of the trends of the most invasive marine alien species.

Scientific references

Indicator definition

The indicator for the marine and estuarine species represents the cumulative number (i.e. the sum) of primary producers (plants), invertebrate and vertebrate alien species that have been recorded in European waters since 1950


Number of species per group (primary producers, invertebrate and vertebrates) at Pan-European level, at regional level (MSFD area) and at country level (only countries with marine borders).


Policy context and targets

Context description

Increase in trade, tourism and maritime, as well as the development in aquaculture, and fisheries, have provided new and enhanced pathways for the spread of alien invasive species. Although European states have a comprehensive regulatory framework to protect economic interests against diseases and pests, these are often inadequate to safeguard against species that threaten native biodiversity. Moreover, the regulatory system pertains to pathogens while large sized species that may have considerable impact on health, economy are not considered to date.


The Convention on Biological Diversity (CBD) has recognized an urgent need to address the impact of Invasive Alien Species and has included ´Trends in invasive alien species’ in the trial indicators to be developed and used for assessing global progress towards the 2010 target.
In Europe, trends in invasive alien species is one of the SEBI2010 WG5 indicators, which has been materialised for the marine environment by exhibiting trends in MAS (Marine alien species).

Both MSFD and WFD have recently included «Non Indigenous species» among indicators required for assessing /setting the overall objective which is Good Environmental Status (to be restored or maintained by 2020) and Good Ecological Status (to be reached by 2015) respectively. Trends in MAS related to shipping, aquaculture, trade will be a tool towards this particularly in hot spot areas such as ports, lagoons, aquaculture areas. A levelling- off the current increase in cumulative numbers of alien species and a reduction in the rate of establishment of alien species in new countries/regions by MAS and/or a shrinking distribution of these within European Seas would be a signal that this target is addressed successfully.

Related policy documents

  • Animal health legislation
    various directives
  • COM(2008) 789 Final
    Communication from the Commission to the Council, the European Parliament, the European Economic and Social Committee and the Committee of the Regions Towards an EU Strategy on Invasive Species [SEC(2008) 2887 Et SEC(2008) 2886
  • Council Directive 90/220/EEC of 23 April 1990
    Council Directive 90/220/EEC of 23 April 1990 on the deliberate release into the environment of genetically modified organisms
  • Council Regulation (EC) No 708/2007 of 11 June 2007
    Council Regulation (EC) No 708/2007 of 11 June 2007 concerning use of alien and locally absent species in aquaculture. Applying to any non-routine intentional introduction of alien or locally absent aquaculture species. Publicly available register on all introductions and translocations of alien or locally absent aquaculture species (applications, permits, monitoring). Monitoring for all alien or locally absent aquaculture species after their release (2 years or full generation cycle or longer). Contingency plans for non-routine introductions or pilot releases of alien or locally absent aquaculture species, to be implemented in case of negative effects on the environment or on native populations
  • European Commission (2006). Proposal for a Council Regulation concerning use of alien and locally absent species in aquaculture.
    COM(2006) 154 final: 32 pp.
  • Marine Strategy Framework Directive 2008/56/EC
    Directive 2008/56/EC of the European Parliament and of the Council of 17 June 2008 establishing a framework for community action in the field of marine environmental policy (Marine Strategy Framework Directive)
  • Water Framework Directive (WFD) 2000/60/EC
    Water Framework Directive (WFD) 2000/60/EC: Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy.

Key policy question

Are marine invasive aliens increasing in European Seas?

Specific policy question

Is the number of alien species in European Regional Seas (MSFD areas) increasing or decreasing?



Methodology for indicator calculation

A simple information system herein called HCMR/EEA database has been developed in HCMR since 2002 to serve as a resource in developing a trends indicator and for reporting to  EEA. The Mediterranean component of it has been transferred to EASIN. Data is available for all European countries both at country level and at MSFD level (Baltic Sea, North Sea, Icelandic Sea, Celtic, Iberian Shelf+ Biscay,  4 Mediterranean, Black Sea). Details are currently archived for 2487 aquatic species, and 7795 records at both country and MSFD level. Harmonisation of  the HCMR/EEA database with European marine alien species databases was an EEA exercise in 2009 towards updating the marine alien species trends indicator the SEBI2010.
For countries with borders in more than one MSFD area, the species belonging to each area have been sorted out after consultation with experts such as in UK, Denmark; and/or by investigating the national databases such as in Sweden, Norway; and/or based on scientific reviews such as for Germany; or in the case of Mediterranean countries from the Marine Mediterranean Invasive Alien Species database which encompasses the MSFD area distribution.
The list of national experts contacted is presented below.

The year of first collection date  (or first report when the former is missing) has been compiled for each MSFD area separately.  For the Pan European analysis, the very first collection/reporting date is considered.
Number of new introduced marine (including brackish waters) alien species is presented per decade since 1950 at Pan European level and per MSFD area.
Information is broken down per selected taxonomic groups:  vertebrates, invertebrates and plants (chromista, vascular plants, algae and fungi).  The vast majority of animals exempting fish and Mammalia are classified as Invertebrates. Birds have been excluded from calculations.

Established, non established and cryptogenic species are considered. Very old records reported as «extinct» in the literature and species suspected to be present due to natural expansion from one MSFD area to the neighbouring one, are excluded from calculations.
In the graphs  that follow, each of the MSFD is treated separately, i.e., introduced species in more than one MSFD have been recorded in each of them. Care has been taken to ensure that the nomenclature problems encountered (e.g., the same species recorded in different regions, lists, or data banks with different names, i.e., synonyms) have not resulted in multiple separate recordings. Scientific literature published lately (2009-2013) has sorted out taxonomic problems and revised nomenclature in some cases (i.e. Marenzelleria, Mnemiopsis). Thus, some species, which are reported as aliens in national databases, have been excluded as native ones. Synonyms of species reported differently in existing European systems have been sorted out by using the nomenclature of WoRMS (World Registry of Marine Species) WoRMS Editorial Board (2013). World Register of Marine Species. Available from at VLIZ.

In an case, the HCMR/EEA database is continually updated based on:  
a) latest updates of European online databases such as DAISIE, NOBANIS, ESENIAS, AquaNIS,
b) annual reports of the ICES  Working Group on Introduction and transfers of Marine Organisms and ICES/IOC/IMO Working Group on Ballast and Other Ship Vectors. The group meets annually and function through extensive collaboration by expert scientists from all over the world, representing leading knowledge and expertise on this topic. They keep annual records on new invasions in the ICES area and provide management advice upon request
c) results of research projects such as PERSEUS, COCONET, VECTORS
d) scientific publications –see list of latest publications per MSFD area
e) personal communication  with renown scientist

Methodology for gap filling

Personal communication with national experts and taxonomic experts - see list of contacted experts below.
When exact data of alien reporting is not known the year of the relative publication has been used.

The following individual local experts were contacted:

Belgium: Sonia VANDERHOVER, Etienne BRANQUART, Francis KERKOFF
Denmark: Kathe Rose JENSEN, Mads THOMSEN
Estonia: Henn OLJAVEER, Andres JAANUS
Finland: Maiju LEHNAMEN, Reetta LJUNGBERG
France: Marc VERLAQUE, Philippe GOULLETQUER, Laurence MIOSSEC
Germany: Ralf BANSTROP, Stephan GOLLASCH, Stefan NEHRING
Italy: Adriana ZINGONE, Carla MORRI
Lithuania: Anastasia ZAIKO
Malta: Patric SCHEMBRI
Netherlands: Rob LEWIS, Hans De BAUWE, Marco FAASE, Herre STEGENGA, 'Arjan GITTENBERGER
Norway: Vivian HUSA
Portugal: Anna AMORIM
Turkey: Melih CINAR

Methodology references



Methodology uncertainty

Year of introduction is based on reported first collection dates but do not necessarily imply true year of introduction that may be years earlier.

For the last 3 years (2011-13) rate of introduction is an underestimate. Species collected in the 2011-13 period are expected to be published in the next 5 years.
In the lack of data on impacts (as well as trends) of most of the introduced species in European Seas, the trends in NIS - marine alien species  (all introduced species) is used as a proxy of the trends of the most invasive marine alien species.

Data sets uncertainty

Data sets even for the Baltic, which is one of the most studied Seas, are often contradicting among official sources such as NOBANIS, HELCOM and the Baltic Seas Alien Species database. The same holds true for the North Sea whose south eastern borders (Kattegat) are overlapping with the Baltic Sea ones.  Individual experts were contacted in many cases.
In the Black Sea it appears that many copepod species were added to the Ukrainian aliens list based on unsubstantial records. Some have been eliminated from the previous list (A. Cubanova  pers. commun.). Yet, the number of marine invertebrates (mostly copepods) is rather inflated and needs further revision.
Cryptogenic species are included by most scientists, excluded by others as native. In many cases historical introductions such as the ship worm Teredo navalis are not perceived as aliens and not included in lists. Species reported from drift material washed ashore are included as casual records.
The list for Mediterranean alien species is still an underestimate as it does not include monocellular algae. Bearing in mind that the diversity of marine microalgae is scarcely known in wide areas of the Mediterranean Sea  it can rarely be excluded that a suspected microalgal invader was already present as part of the rare, hidden and un-sampled phytoplankton, we refrain from citing a detailed list of plankton.
The picture reflects somehow the scientific effort not only in discovering/reporting new species or mapping their distribution but even compiling data at national level.

Rationale uncertainty

Climate change is proved to enhance establishment of alien species (see Raitsos et al, 2010). Consequently, it skews the real magnitude of the phenomenon.

Further work

Short term work

Work specified here requires to be completed within 1 year from now.

Work description

Update lists and collection dates provided by ongoing research and monitoring projects at national level. Analyse the most invasive species as concluded from their spread versus their origin and mode of introduction and impact on ecosystem services.

Resource needs



In progress


2013/01/01 01:00:00 GMT+1

Work description

Update the distribution lists based on data to be collected/reported in the course of future monitoring projects at national level/ compiled lists/databases at national level. Considering the difficulties of reporting new alien species and monitoring the invasive ones, engage citizens and NGOs into reporting selected target species through national/international networks such as the jellyfish watch, eye on earth etc. Expand the existing system by incorporating info on impacts of as many IAS as possible.

Resource needs



In progress


2016/01/01 01:00:00 GMT+1

Long term work

Work specified here will require more than 1 year (from now) to be completed.

General metadata

Responsibility and ownership

EEA Contact Info

Trine Christiansen


European Environment Agency (EEA)


Indicator code
MAR 002
Version id: 1


DPSIR: State
Typology: N/A


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