DEEPHOPE in Oecologia (2024)

The study of sounds produced by animals, whether intentional (communication) or incidental (movement, feeding), provides valuable, non-invasive insights into their behavior and ecology. The diversity and type of sounds produced depend on factors such as the species present, their activity, and their behavior. This approach has already shown that within Mesophotic Coral Ecosystems (MCEs), fish communities vary according to depth and habitat type.

In the present study, the authors explored the same question, but focusing on invertebrates living in MCEs: do the sounds they produce vary with depth and habitat, reflecting distinct communities?

To investigate this, they recorded sounds at 20, 60, and 120 meters depth around six islands in French Polynesia. Two major differences emerged between sounds recorded at 120 meters and those recorded at 20 and 60 meters.

First, sound levels at 20 and 60 meters were higher than at 120 meters. Second, at 20 and 60 meters, sounds were louder at night, indicating a pronounced day-night rhythm in invertebrate activity, whereas at 120 meters, the sounds differed and exhibited distinct temporal patterns. This likely reflects the near-total absence of light at 120 meters, influencing the behavior and composition of invertebrate communities at these depths.

These findings confirm that the communities—or at least the behaviors—of invertebrates at 20 and 60 meters differ from those at 120 meters. This difference may be driven by variations in habitat type: benthic cover shifts with depth, from predominantly hard corals in shallower zones to gorgonians, sponges, and black corals in deeper areas.

Overall, these results demonstrate the value of acoustic monitoring for understanding mesophotic coral ecosystems and their associated biodiversity—a challenging task given the depths involved.

Summary from the article "Invertebrate sounds from photic to mesophotic coral reefs reveal vertical stratification and diel diversity."

Read the full article via the link below. 

Auteurs - Raick X, Parmentier É, Gervaise C, Lecchini D, Under The Pole Consortium, Pérez-Rosales G, Rouzé H, Bertucci F, Di Iorio L.