We used ROV video imagery of a hydrothermal vent field on the southwestern Indian Ridge in the Indian Ocean. Structure from Motion photogrammetry was applied to build a high resolution 3D reconstruction model of an active hydrothermal chimney complex and to project quantified abundances. This technique works for any kind of video imagery, regardless of its initial purpose and can be implemented in marine monitoring and management to identify important ecological areas. Likewise, the reconstruction was used to infer terrain variables at scales of megabenthic specimens, which were related to the abundances of the faunal assemblages. Based on the terrain variables the applied random forest model predicted the faunal assemblage distribution with an accuracy of 84.97 %. The most important structuring variables were the distances to diffuse- and black fluid exits, as well as the height of the chimney complex. This novel approach enabled us to classify quantified abundances of megabenthic taxa to distinct faunal assemblages and relate terrain variables to their distribution. The successful prediction of faunal assemblage occurrences further supports the importance of abiotic terrain variables as key structuring factors in hydrothermal systems.

Correspondence: Klaas Gerdes (klaas.hauke.gerdes@uni-oldenburg.de).Further data available on request:-dense point cloud; filename: 'Pix4D dense point cloud.xyz'-polygon mesh of the reconstructed model; filename: 'Pix4D reconstructed mesh 3D.ply'

Supplement to: Gerdes, Klaas; Martínez Arbizu, Pedro; Schwarz-Schampera, Ulrich; Schwentner, Martin; Kihara, Terue Cristina (2019): Detailed Mapping of Hydrothermal Vent Fauna: A 3D Reconstruction Approach Based on Video Imagery. Frontiers in Marine Science, 6