Damianos Chatzievangelou

• The expansion of the effects of anthropogenic activities towards depths below the shallow continental shelf is constantly increasing, raising questions in relation to the absence of a nationally and globally coordinated monitoring and management plan, partly due to the extreme nature of deep-sea ecosystems. Internet Operated Deep-sea Crawlers operating within a network of seafloor cabled observatories can be the answer to technical and logistical issues that rise from the nature of the previously existing fixed and mobile monitoring platforms, providing long-term, high-frequency, multiparametric environmental and biological data with a broader spatial coverage, and the opportunity for 24/7 remote communication with researchers. In this Thesis I show the use of the crawler “Wally” as a monitoring tool attached to the NEPTUNE Canada cabled observatory, at the methane hydrates site of Barkley Canyon (BC, Canada). In Chapter 2, I assessed the diel behavioral patterns of three benthic megafaunal species (i.e. sablefish Anoplopoma fimbria; pacific hagfish Eptatretus stoutii and a group of juvenile crabs) in relation to fluctuations of oceanographic parameters at the same frequency and the life habits of each particular species (i.e. movement type and trophic level), using linear video-transects conducted with the crawler in June, July and December of 2013. In Chapter 3, I used 18 linear imaging transects (each transect ~ 30 m long), conducted with the crawler in November 2016 to detect changes in the biodiversity of the hydrates community and the spatio-temporal distribution of 7 abundant megafaunal morphospecies (i.e. taxa identified based on morphological traits), with an approach based on the Poisson probabilities of animal encounters. Finally, in Chapter 4 I present the environmental cleaned, re-scaled and calibrated datasets generated by the instrumentation (i.e. ADCP, CTD and current meter) deployed with the crawler during September 2010 to January 2015.