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Damianos Chatzievangelou, Jacobs University Bremen, Germany
Carolina Doya, Institute of Marine Sciences, CSIC, Barcelona, Spain
Laurenz Thomsen, Jacobs University Bremen, Germany
Autun Purser, Alfred Wegener Institute, Germany
Jacopo Aguzzi, Institute of Marine Sciences, CSIC, Barcelona, Spain
High-frequency Patterns in the Abundance of Benthic Species near a Cold-seep – An Internet Operated Vehicle Application

Three abundant benthic megafaunal species (i.e. sablefish Anoplopoma fimbria; pacific hagfish Eptatretus stoutii and a group of juvenile crabs) were tested for diel (i.e. 24 h based) behavioral patterns at the methane hydrate site of Barkley Canyon (890 m depth), off Vancouver Island (BC, Canada). Fluctuations of animal counts in linear video-transects conducted with the Internet Operated Deep-Sea Crawler “Wally” in June, July and December of 2013, were used as proxy of population activity rhythms. Count time series were analyzed together with environmental parameters under the hypothesis that the environmental conditioning of activity rhythms depends on the life habits of particular species (i.e. movement type and trophic level). Non-linear least squares modeling of biological time series revealed significant diel periods for the sablefish in summer months and for the hagfish and crabs in December. Combined cross-correlation and multiparametric methods (RDA) analyses revealed strong relationships among environmental fluctuations and observed megafauna. In particular, sablefish presence in the field of view during the summer months was related to flow magnitude, while the activity of the pacific hagfish and the juvenile crabs in December correlated with change in chemical parameters (i.e. chlorophyll and oxygen concentrations, respectively). Waveform analyses of animal counts and environmental variables confirmed the differences of phase during the 24 h cycle. The timing of detection of sablefish further supported a previously reported diel population displacement within the canyon. Their movement occurred under low flow conditions and against the current direction, a possible behavioral adaptation to the general hypoxic conditions. The proposed effect of chlorophyll concentrations on hagfish counts highlights the potential role of phytodetritus as an alternative food source for this opportunistic feeder. The juvenile crabs seemed to display a cryptic behavior in order to avoid predation, though this was suppressed at early night hours when oxygen levels were at a minimum. Our results highlight the potential advantages such mobile observation platforms offer in multiparametric deep-sea monitoring, in terms of both spatial and temporal resolution.

Special Session 2: Interdisciplinary studies in Barkley Canyon
Poster Presentation
Deep-sea crawler “Wally”, Barkley Canyon, Video-transect analysis, Behavioral rhythms, Benthic megafauna