Inertial bioluminescence rhythms at the Capo Passero (KM3NeT-Italia) site, Central Mediterranean Sea

Abstract

In the deep sea, the sense of time is dependent on geophysical fluctuations, such as internal tides and atmospheric-related inertial currents, rather than day-night rhythms. Deep-sea neutrino telescopes instrumented with light detecting Photo-Multiplier Tubes (PMT) can be used to describe the synchronization of bioluminescent activity of abyssopelagic organisms with hydrodynamic cycles. PMT readings at 8 different depths (from 3069 to 3349 m) of the NEMO Phase 2 prototype, deployed offshore Capo Passero (Sicily) at the KM3NeT-Italia site, were used to characterize rhythmic bioluminescence patterns in June 2013, in response to water mass movements. We found a significant (p < 0.05) 20.5 h periodicity in the bioluminescence signal, corresponding to inertial fluctuations. Waveform and Fourier analyses of PMT data and tower orientation were carried out to identify phases (i.e. the timing of peaks) by subdividing time series on the length of detected inertial periodicity. A phase overlap between rhythms and cycles suggests a mechanical stimulation of bioluminescence, as organisms carried by currents collide with the telescope infrastructure, resulting in the emission of light. A bathymetric shift in PMT phases indicated that organisms travelled in discontinuous deep-sea undular vortices consisting of chains of inertially pulsating mesoscale cyclones/anticyclones, which to date remain poorly known.

Faunal activity rhythms influencing early community succession of an implanted whale carcass offshore Sagami Bay, Japan

“…In this slightly modified model, asymmetry occurs only at a first stage in the downstream current direction ( A ). Over time span of days to months, highly mobile scavengers and predators moving along the main bidirectional tidal currents 17 , 22 , 34 , 35 , split the asymmetry initially at the main bi-directional current flow (E–W in our present study; C ). ( D ) Over longer times scales, from months to a year, depending on the initial mass of the carcass, the spatial footprint would become homogeneous in all directions due to large faunal displacements along and across depth contours ( B ).…”

“…Furthermore, at those depths in the slope (i.e., approx. 500 m), we expected that animal behavior would be largely decoupled from photoperiod-related cues, even though the ocean disphotic layer is variable and can reach 800–1000 m 17 , 34 , 35 . Unfortunately, the lack of information on light spectrum penetration and attenuation for those slope depths in the study area off Japan prevent us from further exploring the role of photoperiodicity in controlling benthic and benthopelagic species behavioral rhythms.…”

A Flexible Autonomous Robotic Observatory Infrastructure for Bentho-Pelagic Monitoring

“…Synchronization of biological activity in deep-sea benthos may also occur in relation to day-night cycles in an indirect fashion; i.e., mediated by the intermittent presence and absence of deep-scattering layers of predators and preys, rhythmically appearing within the benthic boundary layer over a 24-h period (e.g., [44]). Such rhythmic dynamics may also be accompanied by not yet quantified changes in background illumination at the seabed caused by bioluminescence of the scattering layers [45]. If such rhythms influence species relative abundances and community composition towards the continental margins where observatory networks are deployed, a temporal variability in measured ecological indicators (species abundance, biomass as well as biodiversity) must be expected [4].…”

Exo-Ocean Exploration with Deep-Sea Sensor and Platform Technologies

“…Other systems use a stimulating grid mounted on oceanographic instruments, such as CTD, to obtain vertical pelagic profiling of bioluminescence via photomultiplying cameras (e.g., the Image Intensified Silicon Intensifier Target-ISIT; the Image Intensified Charge Coupled Device for Deep-sea Research, ICDeep; e.g., Craig et al, 2015). Alternatively, other imaging systems have been developed, that is, the extreme low-light working LuSEApher camera with photon counting capability (e.g., Barbier et al, 2012;Dominjon et al, 2012) Other means for measuring the bioluminescence of organisms are provided by deep-sea neutrino telescopes (Martini et al, 2016;Aguzzi et al, 2017). Their mooringlike towers cover the benthopelagic dimension and are primarily instrumented with thousands of photon-detecting sensors (i.e., photomultiplier tubes, PMTs) (FIG.…”