What is it: 

Sargassum muticum, (wireweed), is an invasive non-native brown alga originally from Japan but now found extensively in Europe and North America. It is a fast-growing species able to form dense stands where conditions suit and by virtue of its life-history traits, is ideally suited to spread rapidly once established in a new region.

Fronds of the alga readily become detached and can then disperse via natural drift. Crucially, these fronds can remain reproductively active for several weeks enabling dispersal over a wide area. S. muticum was first recorded in the UK in 1973 but did not reach Scotland until 2004 when it was found in Loch Ryan. It has subsequently spread up the west coast of Scotland.

Links to Scotland's Marine Atlas: 
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