View source for Invading species in the Baltic Sea



== Previous changes==

===Invading species===
Over 100 new [[species]] established themselves in the [[Baltic Sea]] during the 20th century. This is a significant addition to the biodiversity of this species-poor, brackish sea, which only supports approximately 900 species altogether. Since the Baltic is young in evolutionary terms (<3,000 years old), its colonisation is probably not complete, and newcomers are easily filling available space and [[ecosystem function|ecosystem functions]]<ref name="ma">[https://www.researchgate.net/publication/306030378_Marine_Biodiversity_and_Ecosystem_Functioning Heip, C., Hummel, H., van Avesaath, P., Appeltans, W., Arvanitidis, C., Aspden, R., Austen, M., Boero, F., Bouma, TJ., Boxshall, G., Buchholz, F., Crowe, T., Delaney, A., Deprez, T., Emblow, C., Feral, JP., Gasol, JM., Gooday, A., Harder, J., Ianora, A., Kraberg, A., Mackenzie, B., Ojaveer, H., Paterson, D., Rumohr, H., Schiedek, D., Sokolowski, A., Somerfield, P., Sousa Pinto, I., Vincx, M., Węsławski, JM., Nash, R. (2009). Marine Biodiversity and Ecosystem Functioning. Printbase, Dublin, Ireland ISSN 2009-2539]</ref>. 

===Examples of invading species===
For example, the roundhead goby ([http://www.marinespecies.org/aphia.php?p=taxdetails&id=126916 ''Neogobius melanostomus'']) from the [[Black Sea|Black]] and Caspian Seas is now playing the previously-vacant role of small, coastal predator on bivalves. At present, there are no documented examples of any negative ecological impact of these new species on the Baltic ecosystem.

A number of new [http://www.marinespecies.org/aphia.php?p=taxdetails&id=1207 gammarid]
amphipods frequenting the southern Baltic coast are well mixed with resident species and all show irregular ups and downs in abundance. However, small-scale problems for humans
have been recorded, such as local problems with pipelines clogged with the zebra mussel [http://www.marinespecies.org/aphia.php?p=taxdetails&id=181565 ''Dreisena''], or fishing nets covered by the copepod [http://www.marinespecies.org/aphia.php?p=taxdetails&id=234024 ''Cercopagis''].

A number of former invaders are now playing an important role in the [[benthic]] system. The bivalve [http://www.marinespecies.org/aphia.php?p=taxdetails&id=140430 ''Mya arenaria''], which arrived from North America during the medieval period, is now one
of the [[keystone species|key species]] and sediment bioturbators, and it is also a source of food for fish and birds. The sessile barnacle, [http://www.marinespecies.org/aphia.php?p=taxdetails&id=106218 ''Balanus improvisus''], a 19<sup>th</sup>-century invader, is now one of the few species that builds stable biogenic structures (it is a bioconstructor and habitat builder) in this system<ref name="ma"/>. 

===Changes in native species===
So far, the only documented extinction from the Baltic Sea is the sturgeon, [http://www.marinespecies.org/aphia.php?p=taxdetails&id=126279 ''Acipenser sturio''], a species that is now also believed to be a medieval invader from North America.

Shifts and changes have occurred before. In the early 20<sup>th</sup> century, the dominant top predators in the Baltic were marine mammals ([http://www.marinespecies.org/aphia.php?p=taxdetails&id=137080 gray], [http://www.marinespecies.org/aphia.php?p=taxdetails&id=159021 ringed] and [http://www.marinespecies.org/aphia.php?p=taxdetails&id=137084 common seal] and [http://www.marinespecies.org/aphia.php?p=taxdetails&id=137117 harbour porpoise]). The seal populations declined by about 95% during the last century as a result, initially, of hunting (1900–1940) and later of [[Portal:Ecotox|toxic pollutants]] (1965–1975)<ref name="ma"/>.

== Predictions==

[[Climate change]]-related increases in temperature will provide the opportunity for more new species to settle in the Baltic Sea. However, all of the new species will have to cope with the effect of [[Effect of Climate Change in the Baltic Sea Area|decreasing salinity]], which forms the key environmental factor structuring this ecosystem, and it will probably continue to remain a key factor in the future<ref name="ma"/>.

==Related articles==
:[[Baltic Sea]]
:[[Effect of Climate Change in the Baltic Sea Area]]
:[[Non-native species invasions]]


==References==
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[[Category:Baltic]]
[[Category: MarBEF Wiki]]
[[Category:Climate change, impacts and adaptation]]