A novel use of Stereo Baited Remote Underwater Video and Drop-Down Video for biodiversity and marine landscape mapping and prediction

PLOS ONE | https://doi.org/10.1371/journal.pone.0319355 April 3, 2025 8 / 23 PLOS ONE Marine landscape and biodiversity mapping using SBRUVs and DDV be geolocated using the latitude and longitude for the start and end of the tow. Each image was then split into 100 grid cells, as per the SBRUV images, and the proportional coverage of each image was calculated using the coverage of substrate in each cell. Species were not recorded using DDV as the movement across the seafloor for recording substratum is continuous, and DDV has a smaller field of view, DDV were only used for substratum analysis. Biodiversity and seabed mapping Using the maximum number of individuals of a species captured in each SBRUV deployment (MaxN), both mobile demersal (e.g., Gadus morhua, Eutrigla gurnardus, Limanda limanda) and epibenthic species (e.g., Asterias rubens, Ophiothrix fragilis, Aphrodita aculeata) were identified to species level (Table S1), in order to calculate biodiversity for each site, all mod- elling was carried out using R software [60], and Simpson’s diversity was calculated for each SBRUV deployment using the rdiversity package [61]. Simpson’s diversity Index was used as a measure for biodiversity as it provides average proportional abundance of each species within a dataset. Biodiversity was then interpolated using ordinary kriging across the whole extent of Fig 5. Grid overlay (10 × 10) of drop-down video (DDV). Screen grab from DDV camera showing 10 × 10 grid overlay of image

depicting substrata composition of South Arran survey point Station 11a, each grid cell was classified by the substrata which com- prised > 50% of each grid cell. https://doi.org/10.1371/journal.pone.0319355.g005 Table 3. Sediment size and classification †maerl could not be taken into consideration independently due to the small area. Sediment Type Sediment composition Expected Particle size (cm) Pebble Small to medium stones and shells ~4–6 Gravel Mixture of stone, shell and maerl † ~2 - 4 Sand Soft sedimentary sand including seagrass when present ~ 0.1–2 Mud Silty sediment high period of water column suspension <0.1 https://doi.org/10.1371/journal.pone.0319355.t003