Deep-sea biodiversity at the extremes of the Salas y Gómez and Nazca ridges with implications for conservation

Macrouridae at RN/SyG (�X = 0.53 ± 1.02) were 43% times higher than at Desventuradas (�X= 0.37 ± 0.69) and accounted for an additional 7.31% of the dissimilarity between subregions. Deployments within subregions were highly dissimilar, with the average similarity among deployments at RN/SyG equal to 14.47% and the average similarity among deployments at Desventuradas equal to 15.99%. Fish-habitat relationships The best distance-based linear model solution between environmental variables and fish assemblage structure included depth, salinity, crust age, nitrate, and broad-scale BPI (AICc = Table 1. Distance-based linear model for invertebrate assemblages and environmental variables. Sequential tests Multiple partial correlations Variable AICc SS(trace) Pseudo-F P Prop. Cumul. dbRDA1 dbRDA2 Crust age 357.63 31603 16.432 0.001 0.267 0.267 -0.779 0.546 Nitrate 349.98 16493 10.359 0.001 0.140 0.407 0.559 0.558 BPI broad 349.23 4531 2.974 0.019 0.038 0.445 -0.036 0.425 Depth 349.17 3487 2.361 0.052 0.030 0.475 0.282 0.457 Multiple partial correlations are the relationships between dbRDA coordinate axes and orthonormal X variables. Prop. = proportion of variation explained. Cumul. = cumulative proportion variation explained. https://doi.org/10.1371/journal.pone.0253213.t001 Fig 6. Environmental variables at the deep-sea camera system deployment locations. (A) Crust age (younger ! older: yellow ! red) was extracted for the nearest

seamount to each deployment location. (B) Nitrate levels; bubbles depict nitrate levels at deployment location and depth (low ! high nitrate: small/light ! big/dark). (C) Absolute broad-scale bathymetric position index (BPI); bubbles depict absolute BPI values at deployment location (low ! high BPI: small/light ! big/dark), basemap depicts absolute BPI values of region (low !high: dark blue ! gray). (D) Depth of each deployment; bubbles depict depth at deployment location (small/light ! big/dark: shallow ! deep), basemap depicts bathymetry (deep ! shallow: dark blue ! white). Purple lines in Panel D are 500 m contour lines. Bathymetric data source: Global Multi-Resolution Topography (GMRT) [80, www.marine-geo.org]. https://doi.org/10.1371/journal.pone.0253213.g006 PLOS ONE Deep-sea biodiversity along the Salas y Go´ mez and Nazca ridges PLOS ONE | https://doi.org/10.1371/journal.pone.0253213 June 30, 2021 13 / 27