Disko Fan Conservation Area in the Davis Strait (Eastern Arctic) - Epibenthic Megafauna Database

Study Extent

The images examined in this report came from seven image transects conducted within the former Narwhal Over-wintering Deep-Sea Conservation Area in Baffin Bay. The depths at which images were collected ranged from 400-1000 metres, with individual transect lines running along depth contours of 400 metres, 600 metres, or 1000 metres. Transects were 1-2 kilometres in length. The image data were obtained using the 4K-Camera, or 4KCam , an underwater drop camera system consisting of a high-resolution digital camera (Canon Rebel Eos Ti 12 megapixel) and two flashes enclosed in a cage that permits it to collect images at depths of up to 4 kilometres below the sea surface (Beazley and Kenchington, 2015). The 4KCam was deployed on a winch line over the side of the vessel and towed above the seafloor. The 4KCam’s distance from the seafloor was controlled by raising and lowering the winch line, and the camera and flashes were triggered to collect images each time the lead weight attached to the system made contact with the bottom. Images were collected at 30-60 second intervals for each transect line. As there was no feed to the vessel, all photo locations were blind drops. Each image was assigned a photo file name that consisted of the Consecutive Operation Number (CON) that was associated with the transect and an image number

Sampling

The sampling methodology followed the protocols outlined in the Circumpolar Biodiversity Monitoring Program (CBMP), created by the Council of Arctic Flora and Fauna (CAFF). The mandate of CAFF involves the conservation of Arctic biodiversity and monitoring the long-term impacts of human activities in the region (www.caff.is). As part of this effort, the CBMP aims to establish and harmonise biodiversity monitoring efforts by standardising data collection methods, integrating existing datasets, and improving communication between existing monitoring organisations. While trawl sampling is considered essential in CBMP protocol, image and/or video transects are recommended as a complement to it (Gill et al., 2011). The images collected from these areas were therefore part of a broader sampling effort in which physical samples of megafauna, macrofauna, meiofauna, microbes and abiotic parameters were collected with the goal of establishing baseline biodiversity data for both the sites and the region.

Method steps

1. The images from each transect were examined for their quality prior to analysis, and those that were too dark, too high off the bottom were discarded. Images obscured by sediment clouds covering at least half of the photo were also not analysed. The remaining images were corrected in Adobe Photoshop CS2 using the AutoLevel and SharpenMore functions to optimise their contrast and exposure levels, colour balance, and sharpness. A 4x3 grid layer dividing each image into twelve square cells labeled A-L was then superimposed on each image using batch-processing and Adobe Action Sets, followed by a layer of twelve 1-cm scale bars. Due to the inverse halo effect, a consistent band of cells at the bottom of each image (I-L) was darker than the cells above it (A-H). When analysing the bottom cells, the brightness was increased by 20-25% and the contrast was altered by +10%. The images in this dataset all have these conditions applied to them and include the grid and scale bar overlays.

Disko Fan Conservation Area in the Davis Strait (Eastern Arctic)