The species we find in the UK which are commonly introduced are those which are good at living or growing in man-made environments – i.e. they can be found attached to hard structures like boats, piers or pontoons.

Free-swimming species such as fish and jellyfish have caused big impacts in other parts of the world, introduced when canals like the Suez Canal connect two previously isolated water bodies. Hundreds of species have moved from the Red Sea to the Mediterranean along this pathway.

Marine species can be transported vast distances and no place is remote enough to escape the impact – there is increasing worry about the potential introduction of novel species to the Arctic and Antarctica on visiting boats. These environments could be especially vulnerable to novel species due to their isolation and unique habitats.

At UHI Shetland, we monitor key sites to detect the arrival of new species and track the spread of marine non-natives already present in Shetland. We do this every year by setting out monitoring panels in marinas and harbours as these environments are most at risk. Native and non-native fouling species that like to grow on hard structures settle on these plates. We remove the plates after 3 months or so and identify the different species. This gives us an easy way to look at what’s living under the surface without having to go for a swim.

We have been carrying out this monitoring over the last decade. There are records of 12 marine non-native species in Shetland which is far fewer than are found in the south of the UK, or in mainland Scotland, potentially as a result of the colder waters around Shetland.

However, we still have had a few introductions which have the potential to cause problems. For example, the orange ripple bryozoan, a type of animal where lots of individuals housed in box-like outer skeletons (zooids) which form a larger colony. It was originally from the northwest Pacific but has been found in Scotland since 2010. It is used to cold-waters and can come to dominate fouling communities that grow on hard structures, taking over space from native species.

Some changes might not have such big economic consequences, but can still change how people interact with the environment. The invasive wireweed Sargassum muticum has become the dominant species in rockpools in some areas of the south of England and on the Isle of Man, and because it floats and is very stringy and tough it means people are more likely to trip and fall over when exploring rockpools as it gets tangled around your legs.

Keeping an eye out

It’s important that we detect new arrivals quickly and it is challenging to monitor species over the long coastline so we also rely on members of the public looking out for key species or noticing unusual species while they are out and about. Species we are most concerned about include wireweed, Sargassum muticum, and the Carpet seasquirt, Didemnum vexillum. We have an identification guide that sets out key species we’re interested in hearing about if you find them on Shetland. Any records can be sent via the shetlandcommunitywildlife@outlook.org email address, with a note of where exactly you found something, a description and a photo.

Preventing the spread of invasive plants and animals is something we can all help with. If you are moving equipment or boats, paddleboards or snorkel gear between water bodies, and especially on/off Shetland you should follow “Check, Clean, Dry”. The GB Non-native Species Secretariat website has a lot of information on biosecurity in the UK, including information specific to the marine environment for industry and individuals.