Mapping the potential far field influence of methane seeps on the water column with the Wire Flyer towed vehicle

The sphere of influence of methane seeps in the water column in not well understood and difficult to observe. Shipboard CTD casts and tow-yos will often miss or spatially alias small scale features, making it hard to determine the source location and extent of any detected anomalies. On three cruises to the Costa Rica Margin between 2017 and 2019 the Wire Flyer towed profiling vehicle was used to collect water column sections down to 1000 meters depth. The tows typically sampled a 300 meter depth band with a repeating profile pattern of less than one kilometer. Numerous tows were completed in the vicinity of the Mound 12 and Quepos Slide sites. Persistent turbidity anomalies were observed emanating from both sites extending up to thirty kilometers away. In many instances these features were observed as coherent layers distinct from the background water column and less than 50 meters in thickness. The water column sections were corroborated with CTD casts and used to target water collections to sample the mid-water microbial community. Additionally, the collected oxygen data offer insight into the spatial variability and potential interaction of the seep discharge with the strong minimum in the area.