The mauve stinger jellyfish was rarely seen in British waters until recently. There are now more animals just like it moving into the area, including Chinese mitten crabs and the zebra mussel.
Three years ago, a survey by the Marine Conservation Society found only 25 zebra mussels in a stretch of the River Thames near Richmond. Recently they conducted another survey, and found thousands of the invasive species. They also found a large amount of mitten crabs. Mitten crabs are a threat to native species because they dig into the river bed, washing away mud and making it hard for native shellfish to find shelter.
The invasive species compete with local species for food and habitat, and can wreak havoc on local shipping. The zebra mussel, in particular, has been a bane on the water. They block water pipes and mess up ship propellers with ease, causing millions in economic damage.
A Marine Conservation Society spokesman said,