Non-indigenous species may cause unpredictable and irreversible changes to marine ecosystems, such as predation or competition for indigenous species, modification of habitats and trophic impacts. A variety of economic or human health impacts are possible through, for example, fouling, harmful non-indigenous algal blooms or damage to structures. Over 160 non-indigenous species have been identified in the OSPAR area, but the actual number of introduced species is likely to be greater. This is because long-term monitoring and recording data are limited and identifying the species taxonomically can be difficult. Some species are currently misidentified.
ICES has identified 30 non-indigenous species that have had adverse impacts on ecosystems or human health within the OSPAR area Table 9.1. Most of the non-indigenous species identified are present in two or more Regions (especially Regions II, III and IV). Data for Region V are mainly absent. The main vector for the initial introduction of these species has been mariculture, followed by ballast water from ships, hull fouling and fishing. The most important and widespread impacts are changes to habitats and competition for food and space with indigenous organisms. Many of these species also have economic impacts. Almost all the species concerned were introduced before current measures, some as much as several hundred years ago.
Non-indigenous species in the OSPAR area...
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Box 9.10 Examples of non-indigenous species known to have adverse effects
The Pacific oyster was introduced throughout Europe in the 1970s for cultivation purposes to replace declining populations of the native oyster and the Portuguese oyster. It was assumed that Pacific oysters would not spread to higher latitudes (such as the UK, the Netherlands and Germany) because the waters would be too cold for reproduction. However, the species can tolerate a wide range of temperatures and the free-swimming planktonic larvae can spend up to three weeks in the water column before finding a suitable substrate to settle on. This gives Pacific oyster a wide dispersal range. It is now established or has been detected in Belgium, Denmark, France, Germany, Ireland, the Netherlands and the UK and established populations are reported as far north as Norway and Sweden. In the Wadden Sea, where hard substrate is rare except for mussel beds and oyster shells, blue mussel beds are declining, while populations of reef-habitat building Pacific oysters appear to be increasing. Community structure differs between habitats created by oysters and mussels, with implications for their overall function in the marine environment.
The red king crab, a native of the northern Pacific, was intentionally introduced into Russian waters in the 1960s and by 1976 had migrated to Norway. It is now found in coastal waters throughout northern Norway, where it competes with local predators, modifies habitats and may affect the shellfish industry.
The leathery sea squirt, native to the Pacific coast of Asia, was probably introduced to Europe through fouling on warships during the Korean War. Once introduced to Europe, it was reported on the hulls of ships and leisure craft and may have been spread through movements of oyster stocks and floating port structures on which it is a fouling organism. This species can create a high biomass in sheltered areas that result in competition with other filter-feeders. Young individuals often attach to larger specimens (up to 200 mm) to form clusters and thus the long-lived sea squirt may serve as substrate for other non-indigenous species. Economic impacts arise as a result of fouling, for example on artificial structures in ports or mariculture installations. Some people develop respiratory problems from sprays produced from damaged tissues when removing sea squirts from oysters.
Leathery sea squirt - case study
From left: Pacific oyster, red king crab, leathery sea squirt
The risk of introductions by ballast water has been addressed by OSPAR and HELCOM taking action to ensure the early application of standards consistent with the IMO Ballast Water Convention. Environmental risks related to movements of non-indigenous aquatic species are addressed within the EU by the Regulation concerning use of alien and locally absent species in aquaculture. There are also international risk assessment protocols for assessing the risks of using non-indigenous species in aquaculture.
Ratification and implementation of the IMO Ballast Water Convention should be expedited and followed up with effective enforcement. There is a need to monitor the effectiveness of this and other recently implemented measures on reducing introductions of non-indigenous species. Work under the EU Marine Strategy Framework Directive will provide a focus for this in seeking to ensure that non-indigenous species introduced by human activities are at levels that do not adversely alter the ecosystems.