Halimeda incrassata (Bryopsidales, Chlorophyta) reaches the Canary Islands: mid- and deep-water meadows in the eastern subtropical Atlantic Ocean

Abstract

Abstract Extensive offshore meadows of Halimeda incrassata are documented for the first time in sandy bottoms of La Palma, Canary Islands. Halimeda incrassata forms dense sublittoral assemblages between 20 and 55 m, but isolated populations occur down to 65 m depth. This species currently spreads over an area of 9.14 ha. Population coverage varies with depth, with the highest values at 35–40 m and an average cover of 62.34%. The calcified segments of H. incrassata act as a stable substratum in these soft bottoms for the growth of other macroalgae, such as the rhodophytes Lophocladia trichoclados and Cottoniella filamentosa. Specimens reach lengths of up to 10 cm, shorter than individuals from the Caribbean. Although it is difficult to ascertain whether this species is a recent introduction, there is evidence of a correlation between the increase in population coverage and recent ocean warming, constituting another example of the tropicalization of the marine flora of this region.