The introduction of NIS and their subsequent establishment into aquatic environments, especially in coastal waters, can cause severe environmental, economic and public health impacts. Since the early 1990s when the Marine Environmental Protection Committee (MEPC) of the International Maritime Organisation (IMO) put the NIS issue on the agenda, the issue has gathered an ever increasing weight in marine environmental protection. In 2004, the International Convention for the Control and Management of Ship's Ballast Water and Sediments (BWM Convention) was adopted by the IMO. The Convention requires ships in international traffic to manage their ballast water and sediments (Regulation B-3) to certain standards specified in the Convention (Regulation D-2), as well as keeping a ballast water record books and an international ballast water management certificate. There is a phase-in period for ships to implement their ballast water and sediment management plan, during which they are allowed to exchange ballast water (Regulation B-1) in the open sea under certain premises of depth and distance from the shore (Regulation D-1).
The Convention entered into force 8 September 2017.
In the BSAP (in the Roadmap towards harmonised implementation and ratification of the 2004 International Convention for Control and Management of Ships' Ballast Water and Sediments), Contracting Parties agreed to adjust/extend by 2010 the HELCOM monitoring programmes to obtain reliable data on non-indigenous species in the Baltic Sea, including port areas, in order to gather the necessary data to conduct and/or evaluate and consult risk assessments according to the relevant IMO guidelines. As a first step, species that pose the major ecological harm and those that can be easily identified and monitored should be covered. The evaluation of any adverse ecological impacts caused by non-indigenous species should form an inherent and mandatory part of the HELCOM monitoring system.
Good Environmental Status (GES) according to the EU MSFD is to be determined on the basis of eleven qualitative descriptors. One of the qualitative descriptors concerns non-indigenous species and describes the GES for this descriptor as 'Non-indigenous species introduced by human activities are at levels that do not adversely alter the ecosystem'.
In order to minimize adverse effects of introductions and transfers of marine organisms for aquaculture ICES drafted the 'ICES Code of Practice on the Introductions and Transfers of Marine Organisms' (ICES, 2005). The Code of Practice summarizes measures and procedures to be taken into account when planning the introduction of NIS for aquaculture purposes. On the European level, the EC Council Regulation No 708/2007 concerning the use of NIS and locally absent species in aquaculture (EC, 2007) is based on the ICES Code of Practice. With a wider scope the recently adopted EU Regulation on the prevention and management of the introduction and spread of invasive alien species, entering into force on 1 January 2015, aims to protect native biodiversity and ecosystem services, as well as to minimize and mitigate the human health or economic impacts that these species can have (EU, 2014).
The introduction of invasive non-indigenous species (NIS) is a severe threat to marine environments. NIS have caused ecological, economic and public health impacts globally (Ruiz et al., 1997; Mack et al., 2000; Lockwood et al., 2007; Ojaveer & Kotta, 2014). NIS can induce considerable changes in the structure and dynamics of marine ecosystems and may also hamper the economic use of the sea or even represent a risk for human health. Ecological impacts include changes in habitats and communities and alterations in food web functioning, in extreme cases even losses of native species can occur (Galil, 2007). Economic impacts range from financial losses in fisheries to expenses for industries for cleaning intake or outflow pipes and structures from fouling (Black, 2001; Williams et al., 2010). Public health impacts may arise from the introduction of pathogens or toxic algae.
Only a minority of all NIS become invasive i.e. have a potential to cause negative impacts. Those NIS which cause the most harm on the environment and/or humans are the most important to assess, not only in terms of assessing the current and changing status of the ecosystems (requirements from the WFD and MSFD), but also in terms of the marine management perspective in order to facilitate strong move towards implementation of the ecosystem based approach.
Documented ecological impact is known only for 43 NIS in the Baltic Sea (Zaiko et al. 2011), which is less than 50 % of the species registered in the sea. According to the biopollution index (e.g. Zaiko et al. 2011), the highest biopollution (BPL = 3, strong impact) occurs in coastal lagoons, inlets and gulfs, and the moderate biopollution (BPL = 2) in the open sea areas. None of the Baltic sub-regions got classified as 'low impact' (BPL = 0 or 1) indicating that invasive species with recognized impacts are established in all areas.
General information about NIS can be found in the Baltic Sea Environment Fact Sheet (BSEFS) 'Biopollution index' that gives more information of the impacts and the BSEFS 'Observed non-indigenous and cryptogenic species in the Baltic Sea' that gives more information on how the baseline was derived. For more species specific NIS information the BSEFS 'Abundance and distribution of Marenzelleria species', 'Abundance and distribution of Round goby' and 'Abundance and distribution of the Zebra mussel' can be referred to.
- Input or spread of non-indigenous species
The indicator evaluates the status of the marine environment affected by anthropogenic pressures. It is important to distinguish between naturally spreading and anthropogenically introduced species. If it is not possible to distinguish between a human mediated introduction and natural spread the species is called cryptogenic. For the indicator all new observed species are therefore first to be treated as NIS or cryptogenic and only species which can be shown to have spread naturally will be removed from the indicator.
According to Minchin et al. (2008), nine main categories of pathways for all aquatic environments through which species may spread can be defined. These are: shipping, canals, wild fisheries, culture activities, ornamental and life food trade, leisure activities, research and education, biological control and alteration to natural waterflow. In the Baltic Sea, the increasing shipping activities and development of the new navigable waterways during the last 60 years has resulted in the increasing number of unintentional introduction of NIS species, transported in ballast tanks or on ship hulls (Olenin et al., 2009). Besides shipping, especially aquaculture has been identified as a very important vector in some parts of the Baltic Sea (Wolff and Reise 2002).