Invasive seaweed choking Scottish Lochs
30/09/2008 18:07:09
Sargassum 'Wireweed'. Credit SNH.
Wireweed
Wireweed is native to the western Pacific but has found its way to these shores. It was first recorded in the UK in 1973 on the Isle of Wight, and has since spread along the south coast of England and into Wales and Ireland. The first reports of the species in Scotland were in Loch Ryan in 2004.
In 2007 SNH launched a public appeal to help track the spread of wireweed, resulting in a number of new records for the Firth of Clyde. This year SNH commissioned researchers to investigate its spread in more detail. The researchers developed models to predict where the seaweed is likely to turn up next, using wind and tide data combined with information on local habitats. These areas were surveyed this summer.
Wireweed spreading faster than thought - Outcompeting native flora September 2008. An alien species of seaweed, which causes commercial and environmental damage, has been found as far north as Loch Sunart in Ardnamurchan and Tarskavaig on Skye, and as far south as Luce Bay in the Solway Firth. The sightings, reported by members of the public, mean that wireweed (Sargassum muticum) has spread much further and much more quickly than previously thought. Scottish Natural Heritage (SNH) has asked the public to continue reporting any sightings to help track its spread.
Originates in the Pacific
Wireweed originates from the western Pacific, where it is harmless, but in the UK it is a nuisance species. A survey carried out this summer to investigate its spread has shown that it is already well established along the west coast of Scotland. Large stands of the weed were found around the islands of Cumbrae and Arran and along the Ayrshire coast near Largs, Ardrossan, Culzean and Maidens. It has also become established on the Kintyre peninsula at Tarbert, Carradale, Campbeltown Loch, Machrihanish and West Loch Tarbert. However the recent finds in Loch Sunart, Skye and Drummore Harbour in Luce Bay show it is spreading fast.
Blocks out the light
Dr Fiona Manson, Marine Advisory Officer at SNH explained: "Wireweed spreads easily and grows very fast. Where it becomes established it grows so densely that it blocks out light to the seabed and stops our native seaweeds growing - this has a knock-on effect on other marine plants and animals. It also has an economic impact, entangling boat propellers and clogging water intakes and fish farming equipment.
"From our survey work this summer we know that wireweed has a firm foothold in the west of Scotland, since it was first reported in 2004. But the recent sightings in Loch Sunart, Skye and Luce Bay highlight the value of others keeping an eye out for it as well. Sightings from members of the public have been crucial in helping us build up a picture of how wireweed is spreading, so please keep them coming in."
Wireweed control
Future work by SNH aims to investigate ways of controlling wireweed and preventing it spreading further, as well as looking at the impact it is having on native wildlife.
Fiona added: "Unfortunately there is very little we can do to control wireweed and natural dispersal is difficult to stop, but human activity can inadvertently cause wireweed to "jump" greater distances along the coast. So the public can also help by being extra careful if they use boats - always clear the seaweed off the anchors, and follow good practice when moving shellfish, such as oysters and mussels, for cultivation."
Help spot wireweed
Coastal walkers, boat users and recreational divers are particularly asked to look out for wireweed. The seaweed can be seen either washed up on beaches, out on the water, or entangled with anchors. Anyone who spots it can report the sighting, with a location or grid reference if possible, by emailing wireweed@snh.gov.uk or by calling Dr Fiona Manson on 01738 458641. Information about wireweed, and what to look for, can be found at www.snh.org.uk/wireweed .
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