DEEPLIFE in Coral Reefs (2025)

The study of mesophotic ecosystems (30 to 200 m) remains a technical challenge, resulting in gaps in our knowledge of these habitats. In the Canary Islands archipelago, mesophotic black coral forests are widespread and exhibit impressive densities and sizes, with some colonies reaching up to 2 meters in height. As an ecosystem-engineering species, they provide shelter, breeding sites, and feeding areas for the mobile fauna associated with these forests.

The Canary Islands, besides their volcanic origin, are quite unique: the islands, arranged along a west-east axis, experience different environmental conditions. Around El Hierro, at the western end, the waters are warm and nutrient-poor. About 400 km east of El Hierro, Lanzarote lies closer to Africa and receives cold, nutrient-rich deep waters brought to the surface by currents along the African coast (upwelling process).

Here, the authors sought to assess whether mesophotic black coral forests on different Canary Islands hosted distinct associated animal communities. To answer this question, the team collected the epifauna (mobile animals living on corals) from colonies of the black coral Antipathella wollastoni around three islands: El Hierro in the west, Gran Canaria in the center, and Lanzarote in the east.

First, the black coral forests differed from island to island, even though it was the same coral species at the same depth (60 m): colonies were sparser and smaller at El Hierro and Gran Canaria, whereas they were denser and taller (up to 2 meters) at Lanzarote.

Next, in each forest, amphipods dominated the epifauna, representing 92% of the approximately 2,700 animals collected, belonging to 12 species. Indeed, forests on different islands hosted distinct epifaunal communities:

• Some species were found only on a single island, while others were present on all islands.
• Amphipod abundance was higher at Lanzarote (cold, nutrient-rich waters) than in the other two forests. Moreover, at Lanzarote, larger colonies hosted higher abundances, reflecting the fact that bigger colonies offer more living space and shelter.
• At El Hierro, amphipods were larger, and species richness was higher than at Lanzarote.

Finally, by examining the contents of their digestive tracts, the authors showed that amphipods could adapt their feeding habits depending on the main resource available on each island (animals, detritus, algae…). Amphipods at Lanzarote fed more on animals, while those at El Hierro fed more on algae.

The authors demonstrated that environmental differences between islands influence the structure of epifaunal communities, as well as the morphology and diet of amphipods, even though the forests are built by the same black coral species and occur at the same depth (around 60 m). Further studies are needed to better understand the capacity of this fauna to adapt to environmental gradients in mesophotic animal forests.

Summary from the article "Inside the mesophotic zone: taxonomic and trait diversity of epifauna associated with black coral forests across an oceanic archipelago."

Read the full article via the link below. 

Authors - Navarro‑Mayoral S, Diaz-Vergara S, Bosch N E, Tuya F, Bramanti L, Fernandez-Gonzalez V, Terrana L, Espino F, Haroun R, Under The Pole Consortium, Otero-Ferrer F.