[All-postdocs] Bioseminar - Xavier Raick

[Ana Velez]

Woods Hole Oceanographic Institution
Biology Department Seminar

Thursday, March 27, 2025 - 12:00 pm, Redfield Auditorium

Xavier Raick
Postdoctoral Research Fellow, Cornell University

Depth-Related Variations and Offshore Range of Biophony in Polynesian Coral Reefs
In the ocean, major biophonic sources include benthic invertebrates, fish, and marine mammals. This acoustic activity can be studied at two levels: at the level of individually identifiable sounds from generally nearby sources of the biophony and at the level of 'mass-phenomena', i.e., continuous noises resulting from the calls of many individuals vocalizing simultaneously. This presentation will focus on French Polynesia for three reasons: the high concentration of coral reefs in the South Pacific, their relatively good preservation, and the scientific knowledge accumulated in Moorea Island. The main objective of this research was to determine how the diversity of the biophony of photic and mesophotic French Polynesian coral reefs varies. We studied the spatiotemporal variation of both the 'mass-phenomena' and individually identifiable sounds of the biophony. The biophony of French Polynesian coral reefs consist primarily of fish sounds and broadband transient sounds emitted by benthic invertebrates. From the reef to the open ocean, this biophony can propagate up to 90 km, although maximal detection distances vary depending on the physical characteristics of the water column and bottom nature, the species and life stage, ranging from less than 0.5 km to 22 km. However, these distances can be reduced due to meteorological conditions and anthropogenic noise. Across the vertical gradient, benthic invertebrate and fish sounds display a stratification primarily determined by depth. We have observed similarities between the sonic morphology of fish species in French Polynesia and well-known temperate sonic species within the same families. Moreover, similarities between sounds from these temperate species and unidentified sounds previously recorded in Polynesian mesophotic coral ecosystems (MCEs) were highlighted. In photic reefs and upper MCEs, sounds produced by benthic invertebrate were louder at night. However, in lower MCEs, the activity rhythms of benthic invertebrates exhibited low or highly variable levels of diel variation. Nonetheless, a distinct peak in the number of BTS was observed between 7 and 9 PM at a depth of 120 m, potentially indicating the presence of cyclic activities of a particular species and supporting the existence of different invertebrate communities in deep mesophotic reefs. Concerning fish sounds, depth has been shown to have an influence on diel cycle and the width of realized acoustic niches.

For questions, contact:

Ana María Vélez
Administrative Associate
Ph: (+1)(508)289-2334
[signature_1005462319]

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