Fig 1.
Topo-bathymetric map of the northern Catalan margin.
Locations of the study area and the main rivers draining into the margin are indicated.
Fig 2.
Bathymetric map of La Fonera canyon head and its neighbouring continental shelf and upper slope.
Locations of the three main canyon branches (Cap de Begur, Illa Negra and Sant Sebastià), the ROV observations used in this study and the Sant Sebastià fishing ground are indicated.
Fig 3.
Bathymetry-derived parameters and backscatter of the study area.
A: Backscatter data, represented in dimensionless digital number. B: Seafloor gradient. C: Fine-scale bathymetric positioning index (FS BPI). D: Broad-scale bathymetric positioning index (BS BPI). E: Seafloor curvature. F: Seafloor rugosity.
Table 1.
Details of the ROV transects carried out in La Fonera canyon head.
Table 2.
Classification scheme of the benthic terrain modelling of La Fonera canyon head and surrounding shelf and slope.
Fig 4.
Benthic terrain classification of the study area.
Note that the upper wall is well defined in the western canyon wall, and that near-vertical walls are located mostly at the lower parts of canyon walls.
Table 3.
Areal distribution of the different terrain classes identified in La Fonera canyon head and nearby shelf and slope.
Table 4.
ROV inspection effort for each terrain class along each transect and for the whole survey.
Fig 5.
Substrate types in the study area.
A: Substrate types observed along ROV dives: muddy bottom, sandy bottom and hard substrate. See text for clarification of this classification. Locations of ROV images in this figure (B to G) as well as in S1 and S2 Figs are provided. B: Rock outcrops on the western wall of Cap de Begur branch (134 mwd, upper wall) with a variety of organisms. C: Rock outcrops with overhangs and caves on the western wall of Cap de Begur branch (290 mwd, near-vertical wall), with small M. oculata and C. rubrum colonies. D: Rock blocks covered by a cm-thick mud veneer on a sedimented area at the eastern wall of the canyon close to Sant Sebastià fishing ground (391 mwd, divide). E: Bioclastic sand and fine gravel along the axis of Illa Negra branch (182 mwd, incised canyon). F: Sandy bottom in the western rim of Cap de Begur branch (123 mwd, canyon rim) with polychaete Lanice conchilega. G: Muddy bottom with some L. conchilega specimens along the axis of Cap de Begur branch (297 mwd, incised canyon).
Table 5.
Substrate types, CWC, red coral and litter observations for each terrain class.
Fig 6.
ROV observations of corals and human impacts.
A: Positive observations of living M. oculata colonies. B: Positive observations of living D. cornigera colonies. C: Positive observations of living C. rubrum colonies. D: Positive observations of litter (all types) and bottom trawling evidences on the seafloor.
Fig 7.
Frequency and occurrence rate vs. depth of observed corals and litter.
A: M. oculata by depth range. B: D. cornigera by depth range. C: C. rubrum by depth range. D: Litter items by depth range. In all panels, background grey histogram indicates frequency of ROV observations, whereas red histogram indicates frequency of observation of each species or litter items. Black line indicates occurrence rate, that is, number of positives with respect to total observations for each depth range.
Fig 8.
Cold-water and red coral colonies imaged by ROV.
A: Locations of ROV images in this figure (B to G) as well as in S3 and S4 Figs. B: Dense overhanging M. oculata living colonies at the foot of Cap de Begur eastern wall (205 m, near-vertical wall). C: Dense M. oculata and D. cornigera living colonies at the foot of Cap de Begur eastern wall, with decapod Munida sp., polychaete P. tubularia and deep-water oyster N. cochlear (267 m, footwall). D: M. oculata colonies over an oyster-covered rock (N. cochlear) on the western wall of Cap de Begur branch (223 m, near-vertical wall). E: Dense M. oculata living colonies on the western wall of Illa Negra branch, with echinoderm C. cidaris (230 m, steep slope). F: D. cornigera living colony next to echinoderm A. mediterraneus on the upper part of the western wall of Cap de Begur branch (132 m, upper wall). G: C. rubrum living colony on a N. cochlear-covered rock on the southern wall of Sant Sebastià branch (141 m, upper wall).
Table 6.
Bathymetric parameters (depth, gradient, curvature) and backscatter of the grid cells.
Table 7.
Bathymetric parameters (rugosity, broad scale and fine scale bathymetric position index) of the grid cells.
Fig 9.
Maximum entropy prediction in La Fonera canyon head.
A: M. oculata occurrence probability. B: D. cornigera occurrence probability. C: C. rubrum occurrence probability. D: Litter occurrence probability.
Fig 10.
Examples of litter observed on the seafloor of the study area.
A: Locations of ROV images in this figure (B to G) as well as in S6 Fig. B: Longline entangled on M. oculata colonies on the western wall of Illa Negra branch, next to the colonies imaged in Fig 8E (231 m, near-vertical wall). C: Longline resting over dead coral rubble at the foot of a coral colony (next to S3G, S3H and S4A Figs) on the upper part of the eastern La Fonera canyon head wall (273 m, steep slope). D: Fishing net entangled on rock on the eastern wall of La Fonera canyon (256 m, broad slope crest). E: Large fishing net entangled on the rocks outcropping on the western wall of Cap de Begur branch, with Echinus melo (207 m, near-vertical wall). F: Large plastic box, plastic bottle and other debris on the axis of Illa Negra branch, with Echinus cf. acutus (314 m, incised canyon). G: Top of a roman amphora, almost totally buried by sediment at the axis of Illa Negra branch, with unidentified fish (299 m, footwall).
Fig 11.
Examples of trawling impacts observed on the seafloor of the study area.
A: Locations of ROV images in this figure (B to G). B: Trawling mark within a muddy bottom at the western limit of Sant Sebastià fishing ground (182 m, ramp). C: Trawling mark in the upper eastern La Fonera wall (338 m, gentle slope). D: M. oculata capped by fine sediment (387 m, footwall). E: M. oculata partially covered by sediment, with a longline in the background to the right (387 m, footwall).