Canary islands : epifauna communities and black coral forest vary with the island

Authors:

Navarro-Mayoral S, Díaz-Vergara S, Bosch NE, Tuya F, Bramanti L, Fernandez-Gonzalez V, Terrana L, Espino F, Haroun R, Under The Pole Consortium, Otero-Ferrer F. Coral Reefs (2025) 

Article summary: 

Studying mesophotic ecosystems (30 - 200 m) remains a technical challenge, leading to gaps in our knowledge of those habitats. In Canary archipelago, mesophotic black coral forests are among the main habitats, and can be impressive by their density and size, some colonies being up to 2 meters high. As an engineer species, they provide shelter, nursery sites and feeding areas to the associated mobile fauna living in those forests. 

Canary archipelago, in addition of its volcanic origin, is quite particular: the islands, located on a western-eastern axis, present different environmental conditions. Around El Hierro, at the western edge, waters are warm and poor in nutrients. Approximately 400 kms east of El Hierro, Lanzarote is closer to Africa and receives cold, nutrient-rich deep water brought to the surface by currents along the African coast (upwelling process).  

Here, authors aimed to assess whether mesophotic black coral forests from different islands in Canary archipelago held different associated fauna communities. To answer the question, the team has collected epifauna (mobile animals living on coral) on colonies of the black coral Antipathella wollastoni around three islands in the archipelago: El Hierro at the western edge, Gran Canaria in the middle, and Lanzarote at the eastern edge.  

First, black coral forests were different among the islands, despite being the same coral species and at the same depth (60 m ) : colonies were sparser and smaller in El Hierro and Gran Canaria whereas they were denser and taller (up to 2 meters) in Lanzarote.  

Then, in every forest, amphipods strongly dominated the epifauna, being 92% of the approximately 2700 animals collected, belonging to 12 species. 

And indeed, forests from different islands held different epifauna communities: 

• Some species were found on one island only, others being found on every island. 

• Amphipods’ abundances were higher in Lanzarote (cold and rich waters) than in the two other forests. Moreover, in Lanzarote, the taller the colony, the higher the abundance, this reflecting that taller colonies hold more space to live, more shelter, etc.  

• In El Hierro, amphipods were taller and species’ richness (number of species living on one colony) was higher than in Lanzarote. 

• Finally, by looking at their gut contents, authors have shown that amphipods were able to adapt their feeding habits depending on the main resource available on each island (animals, detritus, algae…). Amphipods from Lanzarote fed more on animals, and those in El Hierro more on algae. 

Authors have shown that the environmental differences between islands shape the structure of epifauna communities, and the morphology and diet of amphipods, despite the forests being at the same depth (around 60 m) and the same coral species. Further studies are needed to better understand associated fauna’s abilities to adapt to environmental gradients in mesophotic animal forests.