Vertical structure of reef fish assemblages and light penetration reveal new boundaries of mesophotic ecosystems in the subtropical Southwestern Atlantic

• Published in: Marine environmental research Vol. 198; p. 106527
• Main Authors: Gragnolati, Maisha, Rolim, Fernanda A., Pereira-Filho, Guilherme H., Athayde, Ana Clara S., Ciotti, Áurea M., Motta, Fabio S.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2024
• Subjects: Animals; Atlantic Ocean; Biodiversity; BRUV; Coastal zone; Coral Reefs; Ecosystem; Environmental Monitoring; Fishes - physiology; Marine ecology; Reef fish; Rocky reefs; Subtropical reefs; Atlantic Ocean; Subtropical reefs; Rocky reefs; Marine ecology; Reef fish; BRUV; Coastal zone
• ISSN: 0141-1136; 1879-0291
• DOI: 10.1016/j.marenvres.2024.106527

In the Southwest Atlantic, fisheries and in situ observations suggest that mesophotic reefs occur further south than has been reported in the literature, and a description of these subtropical regions is still lacking. We used Baited Remote Underwater stereo-Videos to explore unrevealed patterns in the vertical structure of fish assemblages on subtropical Atlantic reefs, contrasting shallow and mesophotic habitats. Our data on species turnover and light penetration reveal that in the subtropical Atlantic, the boundaries between shallow and mesophotic habitats occur at depths of 18 m, which is shallower than most previous studies have shown. Generalized additive mixed models identified different environmental and management factors as important predictor variables that explain distribution of fish assemblages’ attributes. Besides adding new evidence about mesophotic limits, we described variations in the vertical structure of fish assemblages, providing important information for the description and conservation of mesophotic environments in subtropical regions. [Display omitted] •Light penetration and species turnover determine boundaries of mesophotic ecosystems.•Shallow and mesophotic zones shelter different species richness and abundance.•Subtropical mesophotic zones do not provide refuge for fishery target species.•Environmental and management factors act in synergy shaping fish assemblages.