Alos J., Tomas F., Terrados J., Verbruggen H. & Ballesteros E. (2016)
Fast-spreading green beds of recently introduced Halimeda incrassata (Bryopsidales, Chlorophyta) invade Mallorca Island (NW Mediterranean Sea)
Molecular Ecology Progress Series 558: 153-158


The Mediterranean marine biodiversity is under a tropicalization process. We present the first record and spread dynamics of the tropical green seaweed Halimeda incrassata (Bryopsidales, Chlorophyta) from the Mediterranean Sea. Plants were observed at two sites in the Island of Mallorca (NW Mediterranean) and species identification was confirmed molecularly. Since the first observation of this alien seaweed in 2011, it has spread rapidly in the shallow subtidal habitat up to ca. 20 m depth of a marine protected area located in Palma Bay. By 2015, this species spread by a factor of 6.75 and extended 2.7 km2, entirely covering 41% of the monitored site. The dynamics of the invasion suggests rapid colonization, establishment and spreading of the species through shallow sedimentary and rocky habitats. H. incrassata has the potential to strongly alter the ecosystem services and functioning of shallow Mediterranean habitats. We encourage authorities to pay attention to the spread of this alien seaweed at larger scales, determine positive and negative effects of the invasion and facilitate research-driven decision making.

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