Marine turf of an invasive alga expels lugworms from the lower shore

Abstract Bare sandy flats at and below low tide level of the Wadden Sea (eastern North Sea, European Atlantic) were observed in 2020 to have been invaded by an introduced grass-like alga, Vaucheria cf. velutina (Xanthophyceae). A dense algal turf accumulated stabilized mud, where resident seniors lugworm Arenicola marina had reworked rippled sand . Algae worms incompatible. Initially, rising patches with alternated bare pits lugworms crowded. Their bioturbation inhibited young algae, while felt established rhizoids clogged feeding funnels worm burrows. Eventually, a mosaic pattern competitors gave way coherent without lugworms. Concomitantly, rich small-sized benthic fauna took advantage novel turf. This exotic may potential for drastically altering ecological web lower shore.