First NameAnne Katharina
Last NameJuliane Wittfoth
Supervisor NameDr. Michael Zettler
UniversityUniversity of Rostock
Keywordsbenthic aquatic, alien species, coastal waters. Marine Strategy, Framework Directive
Publication Date19 July, 2015

Assessment of benthic aquatic alien species in coastal waters  of the southern Baltic Sea with respect to the European  Marine Strategy Framework Directive


The Baltic Sea is a young and brackish, epicontinental sea in northern Europe, including the Kattegat, it has a surface of 415,000 km² and a depth up to 459 m. In its history, the physical and chemical conditions have alternated from fresh to marine, and from well temperate to glacial. Around 7,000 years ago, the Baltic Sea became as it is today. As a result of the last glaciation, after the Weichselian glacial period, which ended 12,000 years ago, most animals are postglacial immigrants and many of the species live close to their salinity tolerance. The salinity can rise up to 20 – 24 practical salinity units (psu) in the Kattegatt and decrease to only 1-2 psu in the inner parts of the large gulfs (e.g. Gulf of Finland). The temperature differs from boreal Atlantic in the southwest to sub-Arctic in the northern most part of the Baltic Sea. These horizontal and vertical gradients influence the native and non-native species
distribution. The concepts to determine the invading species vary not only among countries, but also
among scientists. There is a shift in terminology, noticeably from “introduced species” or “non-indigenous species” in the beginning of the 1990s, to “invasive species” or “aquatic alien species” at the end of 1990s and early 2000s. The IUCN introduced the following definition of alien species in 1999: “Alien species” (non-native, non-indigenous, foreign, exotic) means a species, subspecies, or lower taxon , existing outside of its natural range (past or present) and its dispersal potential (i.e. outside the range it occupies naturally, or could not occupy without direct or indirect introduction, or care by humans) and includes any part, gametes or propagule of such species that might survive, and subsequently reproduce.” With the awareness of these species and the discussion of the consequences of their introduction, another phrase rises up that describes this topic. “Biological pollution” has been used recently
to discuss problems caused by aquatic alien species. Olenin et al. (2007) modified a definition of Elliot (2003) and described this dictum as follows: Biological pollution describes “the impacts of alien invasive species efficiency to disturb ecological quality by having significant effects on: • an individual (internal biological pollution by parasites or pathogens), • a population (by genetic change, i.e. hybridisation), • a community (by structural shift),
• a habitat (by modification of physical–chemical conditions), • an ecosystem (by alteration of energy and organic material flow). The biological and ecological effects of biological pollution may also cause adverse economic\ consequences. “ The immigrations of alien species are differentiated between primary and secondary introductions. If the species exists for the first time in a locality, which is different to the biological province, it is called a primary introduction. More then one primary introduction can occur at the same time. Secondary introduction is used if the species expands from this first location. There exist many possible vectors for species to immigrate to a new location (Fig. 1). In our modern trading society infiltration of alien species by shipping plays a prominent role. Ships transport a wide range of sessile species, platonic organisms (free living
stage) or buried in the sediment and associated individuals. This occurs usually via the ships’ hull fouling or ballast water, and its sediments.

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