Several foreign species now live in Norwegian waters: "Warm summers give them a boost"
In recent years, a number of foreign marine species have been discovered in Norwegian waters, and several of them are spreading rapidly.
The brush-clawed shore crab is one of two types of Asian shore crabs that have established themselves in Norwegian waters.(Photo: Rudolf Svensen, MUST, Institute of Marine Research, Handout, NTB)
NTB.Norwegian News Agency
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Among the species that have gained a foothold in Norway are the Asian shore crab, the brush-clawed shore crab, a large new type of red algae, sea vomit, and a shell species originally native to the Gulf of Mexico.
"These are the ones expected to have the greatest impact on the ecosystem," researcher Vivian Husa at the Institute of Marine Research tells Norwegian news agency NTB.
Several of the species reproduce quickly and compete with local species for both space and food.
Asian shore crabs are spreading quickly
In particular, two types of crabs – the Asian shore crab and the brush-clawed shore crab – have rapidly become very numerous in the Oslofjord and along parts of the southern coast.
Annonse
"They came to Norway in 2019 or 2020 and reproduce four times a year. We still know little about the consequences, but assume they can affect the ecosystem since they eat larvae and similar organisms," explains the researcher.
The crabs have most likely arrived as larvae from neighbouring countries such as Sweden and Denmark.
A new type of red algae has established itself in the Horten and Stavanger areas. The species can grow up to a metre long.(Photo: Erling Svensen, Institute of Marine Research, Handout, NTB)
New shell species in Frierfjord
In Frierfjord in southeastern Norway, researchers have discovered a new shell species not previously recorded in Norwegian waters. The species has not yet been given a Norwegian name.
"The shells have most likely come with ballast water from the Baltic Sea and are originally native to the Gulf of Mexico. There are now very many of them in Frierfjord," says Husa.
Sea vomit spreads on shallow seabeds and displaces plants and animals that depend on each other and live on the bottom.(Photo: Åge Wee / NTB)
"Warm summers give a boost"
Earlier this year, the Institute of Marine Research concluded in a report that the marine heatwave that hit the Norwegian coast last summer shows that climate change is affecting marine ecosystems. This is reported by Science Norway.
This year as well, unusually high surface temperatures have been recorded in the sea off Norway.
"Warm summers give the species a real boost in reproduction," says Husa.
Sea vomit is spreading in western Norway
One of the most problematic newcomers is sea vomit, a colony-forming tunicate species that arrived in Norway in 2020. It spreads quickly and has already been found in several places along the western coast of Norway, according to the species map from the Norwegian Biodiversity Information Centre.
"Sea vomit grows everywhere and has a significant impact on the seabed," explains the researcher.
The spread largely occurs via shipping, and it is difficult to limit.
More species are on the list
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The Biodiversity Information Centre has over 120 species on its 'threshold list.' These are species that have not yet established themselves but have a high probability of coming to Norway.
"One of these is the round goby, a fish that has already established itself along the Swedish coast and that could potentially outcompete Norwegian gobies," says Husa.
