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 12 / 23 PLOS ONE Marine landscape and biodiversity mapping using SBRUVs and DDV maerl both living and dead), ranged from 0–0.76 proportional coverage and was mainly located in deeper areas adjacent to algae stretching along the southern and western coasts. Areas of sand were located to the east of the island (which also contained some seagrass) and to the south, as well as several small patches throughout the MPA. Substrata predictions which met the 0.2 threshold of coverage were divided into patches. Pebble had the most fragmented composition with a total of 49 patches, whereas mud was the most continuous with the majority of coverage contained within two large areas extending beyond the boundary of the MPA (Fig 8). Marine landscape analysis Mud patches combined had the largest overall area (18935 m2 in total across seven patches) and pebble the lowest (147 m2 across 49 patches), but pebble had the highest perimeter to area ratio (RPA) (3.05 SE ± 0.117) followed by gravel (2.00 SE ± 0.270) (Fig 9). Sand had the largest range in perimeter to area ratio (minimum RPA 0.154, maximum RPA 4 – Inter- quartile range (IQR) 3.74) showing a high degree of variability across only nine distinct patches. Four areas of increased biodiversity were identified, these were areas of the upper twenty percent of predicted Inverse Simpson diversity (mean = 3.69, upper 20% > 4.04). Mud and sand had the largest patch areas with a maximum proportional coverage of 1.0 and 0.77

respectively. When examining differences in demersal and epibenthic biodiversity between substrata patches the results of the Kruskal-Wallis chi-squared test were significant (H = 0.018, df = 4, P = 0.009), and a pairwise post-hoc Dunn’s test with a Bonferroni adjustment Fig 8. Predicted substrata patches within the South Arran MPA. Patches of predicted substrata (A) Algae, (B) gravel, (C) mud, (D) pebble, (E) sand and (F) highest Inverse Simpson’s Diversity (top 20% of Inverse Simpson’s Diversity Index, areas with value greater than threshold of 4.04). Landscape patches are coloured individu- ally to illustrate separation, bounding boxes outline MPA fishing restrictions (as described in Table 1). https://doi.org/10.1371/journal.pone.0319355.g008