title: Current-oriented swimming by jellyfish and its role in bloom maintenance.
abstract: Cross-flows (winds or currents) affect animal movements [1-3]. Animals can temporarily be carried off course or permanently carried away from their preferred habitat by drift depending on their own traveling speed in relation to that of the flow [1]. Animals able to only weakly fly or swim will be the most impacted (e.g., [4]). To circumvent this problem, animals must be able to detect the effects of flow on their movements and respond to it [1, 2]. Here, we show that a weakly swimming organism, the jellyfish Rhizostoma octopus, can orientate its movements with respect to currents and that this behavior is key to the maintenance of blooms and essential to reduce the probability of stranding. We combined in situ observations with first-time deployment of accelerometers on free-ranging jellyfish and simulated the behavior observed in wild jellyfish within a high-resolution hydrodynamic model. Our results show that jellyfish can actively swim countercurrent in response to current drift, leading to significant life-history benefits, i.e., increased chance of survival and facilitated bloom formation. Current-oriented swimming may be achieved by jellyfish either directly detecting current shear across their body surface [5] or indirectly assessing drift direction using other cues (e.g., magnetic, infrasound). Our coupled behavioral-hydrodynamic model provides new evidence that current-oriented swimming contributes to jellyfish being able to form aggregations of hundreds to millions of individuals for up to several months, which may have substantial ecosystem and socioeconomic consequences [6, 7]. It also contributes to improve predictions of jellyfish blooms' magnitude and movements in coastal waters.
authors.affiliation: Swansea Laboratory for Animal Movement, Biosciences, College of Science, Swansea University, Singleton Park, SA2 8PP Swansea, UK. Electronic address: sabrina.fossette@googlemail.com.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Fossette
authors.affiliation: Swansea Laboratory for Animal Movement, Biosciences, College of Science, Swansea University, Singleton Park, SA2 8PP Swansea, UK.
authors.forename: Adrian Christopher
authors.initials: AC
authors.lastname: Gleiss
authors.affiliation: Université de la Rochelle, UFR Sciences, LIENSs UMR 7266, 17000 La Rochelle, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Chalumeau
authors.affiliation: Swansea Laboratory for Animal Movement, Biosciences, College of Science, Swansea University, Singleton Park, SA2 8PP Swansea, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bastian
authors.affiliation: Swansea Laboratory for Animal Movement, Biosciences, College of Science, Swansea University, Singleton Park, SA2 8PP Swansea, UK.
authors.forename: Claire Denise
authors.initials: CD
authors.lastname: Armstrong
authors.affiliation: Swansea Laboratory for Animal Movement, Biosciences, College of Science, Swansea University, Singleton Park, SA2 8PP Swansea, UK.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Vandenabeele
authors.affiliation: Université de la Rochelle, UFR Sciences, LIENSs UMR 7266, 17000 La Rochelle, France.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Karpytchev
authors.affiliation: Swansea Laboratory for Animal Movement, Biosciences, College of Science, Swansea University, Singleton Park, SA2 8PP Swansea, UK; Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Warnambool, VIC 3280, Australia.
authors.forename: Graeme Clive
authors.initials: GC
authors.lastname: Hays
mesh_terms: D061725:Accelerometry; D000818:Animals; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D008399:Mass Behavior; D008954:Models, Biological; D009949:Orientation / Q000502:physiology; D037401:Scyphozoa / Q000502:physiology*; D013550:Swimming / Q000502:physiology*; D013997:Time Factors; D014872:Water Movements