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

Abstract

Extensive offshore meadows ofHalimeda incrassataare documented for the first time in sandy bottoms of La Palma, Canary Islands.Halimeda incrassataforms 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 ofH. incrassataact as a stable substratum in these soft bottoms for the growth of other macroalgae, such as the rhodophytesLophocladia trichocladosandCottoniella 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.

Oxidative Stress Response in the Seaweed Padina pavonica Associated with the Invasive Halimeda incrassata and Penicillus capitatus

“…Moreover, the establishment of a stressful condition can occur by nutrient competition as described for Halimeda spp. [39] or by overgrowth as it has been described for P. capitatus [38,39]. In the case of P. pavonica, enzymatic antioxidant activation (SOD and CAT) has been previously reported in stressful situations, mainly derived from a decreased photochemical efficiency under nutrient assimilation shortage and decreased temperature [45].…”

“…This fact is evidenced by a substantial decrease in the number of P. pavonica specimens in the areas where the native algae coexists with the invaders, suggesting that their normal growth and development is affected. Density variations in other areas such as the Canary Islands evidenced that H. incrassata invasion in conjunction with P. capitatus caused strong transformations in previous algal assemblies [38]. Moreover, P. capitatus is known to form assemblies with other tropical taxa in the invaded Mediterranean areas [36].…”

“…Moreover, P. capitatus is known to form assemblies with other tropical taxa in the invaded Mediterranean areas [36]. From previous studies, the quick and high colonization potential of P. capitatus and H. incrassata seem to be due to their invasive capabilities through efficient nitrogen metabolism [39,40], fast growth, and clonal reproduction by rhizoidal extension and fragmentation [10,38]. Moreover, both species have calcareous thalli that, combined with chemical defences, substantially reduce the susceptibility to herbivory in the new occupied areas [41].…”

A Tropical Macroalga (Halimeda incrassata) Enhances Diversity and Abundance of Epifaunal Assemblages in Mediterranean Seagrass Meadows

“…In 2005, its presence was reported on the island of Madeira (NE Atlantic) for the first time (Wirtz and Kaufmann, 2005). At the end of 2008, H. incrassata was detected in La Palma (Canary Islands) (Sangil et al, 2018) and four years later, in 2011, H. incrassata was found colonizing sandy bottoms in the southwestern coast of Mallorca Island (NW Mediterranean) (Aloś et al, 2016), rapidly spreading into different areas of Mallorca since then (Tomas et al, unpublished).…”

“…the sea urchin Paracentrotus lividus and the fish Sarpa salpa) are able to consume invasive macroalgae (mainly C. racemosa), but their capacity to control the invasion is somehow limited (Cebrian et al, 2011;Tomas et al, 2011;Santamarıá et al, 2021). Thus, the combination of defense and reproductive traits provide H. incrassata with a strong potential of invasion and ecosystem modification (Aloś et al, 2016;Sangil et al, 2018). Importantly, because H. incrassata is a habitatforming species with an important ecological role on tropical sandy-bottom habitats (e.g.…”