Ichnofabrics of modern submarine canyons and infaunal response to increased hydrodynamic activity: the Barkley Canyon of Northeast Pacific Ocean

Submarine canyons are hotspots of benthic abundance and biodiversity relative to the open slope. Previous studies in Barkley Canyon, northeast Pacific Ocean, off British Columbia, Canada, have shown an epifaunal community controlled by hypoxic conditions at the core of the oxygen minimum zone, seasonal nutrient input provided via upwelling and downwelling dynamics, and hydrodynamic energy from sea-surface storms, internal tides, and waves. However, studies of the infaunal behavior and resulting bioturbation are scarce. In-situ time-series video data from Ocean Networks Canada NEPTUNE observatory at the canyon axis (985 m deep) made possible to approach the study of modern biogenic structures observed on the sea floor to better understand the pre- and post-turbidic disturbance community response, composition, and structure. During periods of low turbidity, a community dominated by burrowing polychaetes was observed in the video. Sediment push-cores confirmed the presence of high densities of spionid polychaetes in the top 10 cm sediment layer. In contrast, during periods of high turbidity, their density markedly decreases. The spionid burrows comprise a simple ichnofabric produced by one community reflecting a single colonization event. From the perspective of the ichnofacies model, this suite would represent an occurrence of the Skolithos Ichnofacies in a submarine canyon. However, this example from a modern submarine canyon influenced by an oxygen minimum zone, represents a departure from the well-oxygenated conditions that characterize this ichnofacies. This study bridges a substantial gap between the studies of modern and ancient environments introducing a novel interdisciplinary perspective. Combining the conceptual framework of ichnologic analysis and the current knowledge on the physical and biologic dynamics of submarine canyons, the holistic approach of this study aims to provide insights into several facets of these unique systems.