Non-indigenous species are organisms that are expanding to new areas through human actions, intentionally or accidentally. The increase in sea traffic and the speed of ships have heavily affected the spread to new areas. The term “ecological roulette” describes the unpredictability and irreversibility of the changes these species can cause in the ecosystem. The changes are often permanent, because it is impossible to remove the species from the aquatic ecosystem after a permanent population has been established.

There are countless types of plastic, and they contain harmful toxins in their own right. In addition, through chemical reactions, they can bind environmental toxins in the seawater, i.e. they function as adhesive surfaces for PCB compounds, for instance.