Submarine canyons enhance shelfโslope sediment exchange and influence hydrodynamic processes, with consequences for biogeochemical cycles. This work documents variations in the vertical export of biogenic matter on the northern shore of the lower St. A total of three moorings were deployed from November to September The ADCP data revealed the occurrence of a minor sediment remobilization event December and a small turbidity current February in the canyon.
The composition of diatom and dinoflagellate assemblages was similar in the canyon system and offshore BC, but the diatom bloom occurred 2 weeks earlier in mid-April at the PDM site. A bloom of the potentially toxic diatom Pseudo-nitzschia seriata was also observed during the second half of September at the BC site.
Annual diatom and dinoflagellate fluxes were almost 2 times lower at the PDM site than at the BC site, possibly due to differences in riverine input and the structure of the water column, as well as increased sediment input and resuspension at the PDM site, leading to limited light availability.
This study notably helps identify the relationship between near-bed canyon processes and biogenic matter export in the water column, thereby directly influencing the ecosystem offshore PDM. The study period further covered an anomalously nearly ice-free winter, and thus, in the context of climate change, it provides valuable insight into future trends of biogenic matter export in the LSLE.
Sharpe, H. Submarine canyons are erosional features that cut into the seabed of continental margins and slopes. Canyons are preferential particle transport routes from the coast to deep depositional sinks, leading to important sites of sediment accumulation on submarine fans Covault, Owing to their bathymetric complexity, large canyon systems are known to significantly influence hydrodynamic processes and induce shelfโslope exchanges of water and matter through turbidity currents, funneling of internal tides and waves, and enhanced downwelling and upwelling currents, thereby playing a key role in biogeochemical cycling of elements and supporting biodiversity hotspots Fernandez-Arcaya et al.
