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

J Aguzzi,Y Fujiwara,M Kawato,E Fanelli,Y Furushima,C Doya,F C De Leo,C Costa,T Ciuffardi,A Schirone,M Miyazaki

doi:10.1038/s41598-018-29431-5

Abstract

Benthic community succession patterns at whale falls have been previously established by means of punctual submersible and ROV observations. The contribution of faunal activity rhythms in response to internal tides and photoperiod cues to that community succession dynamism has never been evaluated. Here, we present results from a high-frequency monitoring experiment of an implanted sperm whale carcass in the continental slope (500 m depth) offshore Sagami Bay, Japan. The benthic community succession was monitored at a high frequency in a prolonged fashion (i.e. 2-h intervals for 2.5 months) with a seafloor lander equipped with a time-lapse video camera and an acoustic Doppler profiler to concomitantly study current flow dynamics. We reported here for the first time, to the best of our knowledge, the occurrence of strong 24-h day-night driven behavioral rhythms of the most abundant species (Simenchelys parasitica; Macrocheira kaempferi, and Pterothrissus gissu). Those rhythms were detected in detriment of tidally-controlled ones. Evidence of a diel temporal niche portioning between scavengers and predators avoiding co-occurrence at the carcass, is also provided. The high-frequency photographic and oceanographic data acquisition also helped to precisely discriminate the transition timing between the successional stages previously described for whale falls’ attendant communities.

Highlights

The fate of large whale carcasses sinking to the seafloor in both shallow and deep-sea environments has intrigued scientists in several research fields spanning from community ecology, evolution, and biogeography for three decades[1,2,3,4]
Seafloor environmental conditions such as depth, current speeds, temperature, and dissolved oxygen have been postulated to influence in the duration of whale fall community successional stages[2,9]
We reported here for the first time, to the best of our knowledge, the occurrence of a diel turnover in the species assemblages scavenging and foraging at and in the vicinities of an artificially implanted whale carcass at mid slope depths off Japan

Summary

Introduction

The fate of large whale carcasses sinking to the seafloor in both shallow and deep-sea environments has intrigued scientists in several research fields spanning from community ecology, evolution, and biogeography for three decades[1,2,3,4]. The behavioral activity of scavenging species and their access to the whale carrion could be temporally regulated by internal tidal motions, as well as upon the rhythmic presence of benthopelagic predators in the local benthic boundary layer (BBL)[15] These rhythmic displacements all combined could in turn affect the dynamics of energy dispersal from the center of the carcass towards the background seafloor in the form of particulate and dissolved organic matter, and fecal material Interspecific competition between facultative versus obligated scavengers could play a crucial role in regulating species turnover near sunken whale carcasses These two trophic groups may have developed a temporal niche partitioning strategy, accessing the carrion at different times during a 24-h diurnal period[17,18], to avoid competition

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Conclusion