Introduction of new species
Invasive species are one of the great problems of the modern times. Globalization, increase of commercial trades and climatic changes make invasive species a general threat for all kinds of terrestrial, freshwater or marine ecosystems.
Sometime people introduce new species to habitats, or reintroduce species to the place where it was common in previous time, in order to restore natural values or to gain commercial profit.
Example: King-crab in Norway and Russia
In the period of 1980-1985, few thousands of king-crab Paralithodes camtchatica, normally inhabiting the northern part of the Pacific ocean, were transported to Barents Sea. About 20 years later Paralithodes is common along the Norvegian and Russian shore of Kola peninsula; they were later found in the White sea. In 2002 Norway and Russia decided to open quota for fishery, but there are still very limited data how this great crab affects the bottom communities of the Barents Sea. In 2002 the abundance of Paralithodes along the Shoreline of the Kola penincula was so high, that the populations of many invertebtrate species like sea-stars, were seriously treated (just eaten). (Fyodorov, 2002).
However, more often it happens that species are introduced unconsciously or by accident. Effects on the local ecosystem may be considerable.
Tankers, when navigating without cargo (oil), have to fill their tanks by the sea water. It means, that they transport billions of cubic meters of sea water over thousands of miles. In the particular case of tanker navigation by channels and rivers from Caspian Sea to the Black Sea and back, scientists warned authorities, because of the danger of introduction of Mnemiopsis to the very sensitive ecosystem of the Caspian sea, but nothing was regulated (www.caspinfo.ru/library/bulletin/caspvk/1_33.html).
Example: Caulerpa algae in the Mediterranean
Another example is that of Caulerpa algae introduced to the Mediterranean by a unique occasion. One specimen of Caulerpa living in a sea aquarium in Monaco was thrown into the sea. Now this species is occupying large areas through the coast of France and Italy.
Example: Introduction of alien species in the Black Sea
Black Sea is a particular marine basin, with special hydrological characteristics, formed 10,000 years BP, when Mediterranean waters flowed to the Black Sea over the Bosporus strait. The low salinity, low species diversity and highly affected coastal ecosystems by eutrophication combined with the high trade rate in the area have encouraged the establishment of alien species with high ecological plasticity.
Causes of invasion, invasion routes and geographic origin of alien species
The intrusion of alien species in the Black Sea coastal area has similar causes with those encountered in other regions. Most species were accidentally introduced in fouling communities from ships’ hulls and in balast water while other species were introduced for aquaculture and mariculture. First records of most alien invasive species in the Black Sea basin are mentionedfrom the north-western and north-eastern part of the basin, in the vicinity of Odessa, Sevastopol and Novorossiysk harbors. The development ofshipping activities in these areas and the intended species introduction formariculture between 1970 and 1980 are the main causes of the invasive speciesphenomenon in the entire Black Sea. For the marine ecosystems, about 60% of the alien invasive species wereaccidentally introduced with ballast water and about 33% in fouling associations. Only about 6% were intentionally introduced for economic purposes. Forfreshwater ecosystems, the situation is different: the high majority of alien invasivespecies was introduced for aquaculture.
Some alien species examples from Black Sea:
Mnemiopsis leidyi. This ctenophore, the rainbow comb jelly is the invasive species with the highest impact on the associations of zooplanktonic and neriticspecies in the Black Sea.The feeding habits, ecology and the lack of predators combined with the particularconditions of the Black Sea have transformed it quickly into dominant species andits mass development has affected the whole pelagic zone. Among the effects of itspenetration and acclimatization in the Black Sea can be mentioned the drasticreduction of pelagic fish populations.
Ficopomatus aenigmaticus (Annelida: Polychaeta) has proved a particular success in populating the habitats in harbor areas. Resistant in a marine environmentaffected by a high human impact.
Rapana venosa. The veined rapa whelk, the largest species of predatorygastropod in the Black Sea. The impact on native bivalve communities wasimportant since R. venosa contributed at the disappearance of oyster banks from theeastern part of the Black Sea.
Balanus improvisus is the invasive species with the highest ecological successamong the crustaceans. Arrived in the Black Sea in the second half of the 19thcentury.
Alien invasive species are considered those species that established selfsustaining populations in new habitats situated at long distance from their nativehabitat, capable to spread in new territories independent from human activities. We consider in this category established and naturalized alien species, namely those species that are able to develop self-maintaining populations independent of anyhuman activity, after their direct or indirect introduction (EU Commission, 2004). Cryptogenic species were also included in this category, which are speciesintroduced before 1800 with uncertain origin and unknown way of introduction, orspecies with no evidence of their native or non-native status.
Skolka, M. & Preda, C. 2010. Alien Invasive species at the Romanian Black Sea coast-Present and Perspectives