Multi-species consumer jams and the fall of guarded corals to crown-of-thorns seastar outbreaks

Mohsen Kayal (1) , Jane Ballard (2) , Mehdi Adjeroud (3)

1 CEFREM - Centre de Formation et de Recherche sur les Environnements Méditérranéens
2 National Estuarine Research Reserve Association
3 ENTROPIE [Réunion] - Ecologie marine tropicale dans les Océans Pacifique et Indien

Outbreaks of predatory crown-of-thorns seastars (COTS) can devastate coral reef ecosystems, yet some corals possess mutualistic guardian crabs that defend against COTS attacks. However, guarded corals do not always survive COTS outbreaks, with the ecological mechanisms sealing the fate of these corals during COTS infestations remaining unknown. In August 2008 in Moorea (17.539° S, 149.830° W), French Polynesia, an unusually dense multi-species aggregation of predators was observed feeding upon guarded corals following widespread coral decline due to COTS predation. Concurrent assaults from these amplified, mixed-species predator guilds likely overwhelm mutualistic crab defense, ultimately leading to the fall of guarded corals. Our observations indicate that guarded corals can sustain devastating COTS attacks for an extended duration, but eventually concede to intensifying assaults from diverse predators that aggregate in high numbers as alternative prey decays. The fall of guarded corals is therefore suggested to be ultimately driven by an indirect trophic cascade that leads to amplified attacks from diverse starving predators following prey decline, rather than COTS assaults alone

Mots clés: Acanthaster; Density dependence.; Guardian crab; Mixed-species predator guild; Mutualistic defense; Predator outbreak; Trapezia; Trophic cascade; Conceptualization; Investigation; Visualization; Writing – Original Draft Preparation; Writing – Original Draft Author roles: Kayal M Ballard J Preparation; Writing – Review & Editing; Funding Acquisition; Project Administration; Resources; Supervision; Writing – Review &

Domaines: Sciences du Vivant [q-bio]; Zoologie des invertébrés; Biodiversité; Interactions entre organismes

Mohsen Kayal, Jane Ballard, Mehdi Adjeroud. Multi-species consumer jams and the fall of guarded corals to crown-of-thorns seastar outbreaks. F1000Research, 2017, 6, ⟨10.12688/f1000research.13118.1⟩. ⟨hal-01764149⟩