The invasive Japanese giant oyster, known for its sharp shells, is spreading rapidly along Sweden's west coast, posing risks to swimmers and potentially expanding into the Baltic Sea. Marine ecologist Mats Lindegarth highlights the oyster's adaptability and the challenges it presents to local ecosystems.
Invasive Giant Pacific Oyster Poses Growing Threat to Swedish Waters
Invasive Giant Pacific Oyster Poses Growing Threat to Swedish Waters
Have you been one of the many who cut themselves on the Japanese giant oyster while swimming this summer? It's no surprise. In less than 20 years, this mollusk has become one of the most common in Sweden. Its spread may now extend further into the Baltic Sea.
"It seems to be very adaptable," says Mats Lindegarth, professor of marine ecology at the University of Gothenburg.
Swimmers emerge from the sea with stinging cuts on their feet. The razor-sharp Pacific oyster, also known as the Japanese giant oyster, is an invasive species now found from Bohuslän all the way down to the Skåne coast in Malmö.
In Bohuslän, the population is widespread, while there are only isolated cases further south.
"They have developed to become one of the most common mussels we have on the west coast," says Professor Mats Lindegarth.
Growing on Each Other
In his research, he follows the species' progress along the Swedish coast since it was discovered in 2006.
"Exactly how the spread has occurred since then is hard to say," the researcher notes.
The mussel has likely spread with currents from Western Europe, where it was previously imported. Often, the mussels grow on each other, making the water inaccessible for people who want to swim.
"I would say the spread happened surprisingly fast. Today, they are virtually everywhere between Strömstad and Gothenburg. If you look at a 100-meter stretch between those cities, you will definitely find them," says Lindegarth.
Risk of Further Spread
The Pacific oyster, which likes to settle at the water's edge and up to two meters deep, may appear in even more places in the future. In the scientific community, there is a risk that the mussel will spread further into the Baltic Sea. So far, however, there are no documented discoveries in the brackish sea, according to Mats Lindegarth.
"There is a concern that it will spread, but there is not much we can do about it," he says, adding:
"Generally, we want as few new and foreign species as possible, as it is difficult to predict the consequences. Diseases may come in and cause unwanted ecological effects."