The establishment of the invasive non-native macroalgaSargassum muticumin the north of Scotland

Abstract

AbstractThe spread of the brown seaweedSargassum muticumis one of the best documented invasions of a non-native marine species. Observation of a potentially established population ofS. muticumin the Orkney Islands archipelago, located off the northern coast of Scotland, was reported by recreational snorkellers in 2019 and 2020. The present study summarises a focussed investigation to confirm its presence and current local distribution, using data from 46 survey sites monitored as a part of the Orkney Islands Council Harbour Authority monitoring programme. Findings in this study represent the most northerly record of an established population ofS. muticumin the United Kingdom, extending the latitudinal range in this country by 1.44° (159 km) northwards, and indicate only localised presence of this species. Analysis of a partial cytochrome oxidase I gene sequence confirmed the visual species identification. Possible vectors of introduction, gaps in the geographic range, local ecological and economic impacts, and the potential ameliorating factor of deep rockpools on wave exposed shores forS. muticumare discussed.