Unveiling hidden connections using photogrammetry: Multi-scale relationships between benthic communities and rocky subtidal seascapes

The objective of the present study is to unravel the multi-scale processes involved in structuring of infralittoral rocky biocenoses habitat characteristics. A photogrammetric methodology (supervised classification) was developed in three rocky reefs of Saint-Malo bay (∼ 250 km², France) to describe the biotope and the associated benthic community (photo-quadrat and morphotypic approach) along 120-m² transects. The methodology captured more than 70 % of morphotypic richness, and successfully estimated the morphotype proportions. The results confirmed the importance of the broad-scale (> 120 m²) processes as a driver of benthic communities (24 % of variance explained). Interestingly, the photogrammetric metrics revealed that the benthic morphotypic composition was also shaped by fine-scale (< 120 m²) habitat characteristics (18 % and 37 % of variance explained by geomorphology and substrate composition, respectively). Substrate typological patches and geomorphological descriptors also structured the benthic community composition. This study provides tools for characterizing and predicting benthic community characteristics from multi-scale habitat descriptions in temperate rocky reefs.