Algae that choked marine life in huge areas of the North Sea last summer is threatening to take hold in the neighboring Baltic Sea, scientists were quoted as saying.

Polish marine biologist Martin Plinski told the influential Swedish science magazine Ny Teknik there were signs the killer slime was taking hold in areas of the Baltic off the Polish coast."Good algae is disappearing and other smaller species are taking over and competing with the normal flora," Plinski said.

Swedish marine biologist Torgny von Wachenfeldt told the weekly further research was vital to plot the danger to the Baltic.