Influence of a small submarine canyon on biogenic matter export flux in the lower St. Lawrence Estuary, eastern Canada
-
Published:2023-12-18
Issue:24
Volume:20
Page:4981-5001
-
ISSN:1726-4189
-
Container-title:Biogeosciences
-
language:en
-
Short-container-title:Biogeosciences
Author:
Sharpe HannahORCID, Gosselin MichelORCID, Lalande Catherine, Normandeau Alexandre, Montero-Serrano Jean-Carlos, Baccara Khouloud, Bourgault Daniel, Sherwood OwenORCID, Limoges AudreyORCID
Abstract
Abstract. Submarine canyons enhance shelf–slope 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. Lawrence Estuary (LSLE, Quebec, eastern Canada), which is characterized by the presence of an active submarine canyon system. A total of three moorings were deployed from November 2020 to September 2021. One nearshore mooring (PDMc) was deployed in the main axis of the Pointe-des-Monts (PDM) canyon system and was equipped with an acoustic Doppler current profiler (ADCP), and two moorings equipped with sediment traps were deployed in the distal PDM canyon system (PDM-154, PDM-224) and offshore Baie-Comeau (BC-133). The ADCP data revealed the occurrence of a minor sediment remobilization event (December 2020) and a small turbidity current (February 2021) in the canyon. Concurrent elevated fluxes of total particulate matter, particulate organic carbon, particulate nitrogen, and chloropigments showed that these events left a signature in sediment traps PDM-154 and PDM-224 located > 2.6 km further offshore by enhancing lateral dispersion of resuspended sediments. 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 2021 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.
Funder
Natural Sciences and Engineering Research Council of Canada Marine Environmental Observation Prediction and Response Network
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
Reference60 articles.
1. Altabet, M. A., Deuser, W. G., Honjo, S., and Stinen, C.: Seasonal and depth-related changes in the source of sinking particles in the North Atlantic, Nature, 354, 136–139, https://doi.org/10.1038/354136a0, 1991. 2. Altabet, M. A. and Francois, R.: Sedimentary nitrogen isotopic ratio as a recorder for surface ocean nitrate utilization, Global Biogeochem. Cy., 8, 10–35, https://doi.org/10.1029/93GB03396, 1994. 3. Altabet, M. A. and Francois, R.: Nitrogen isotope biogeochemistry of the Antarctic Polar Frontal Zone at 170∘ W, Deep Sea Res. Part II, 48, 4247–4273, https://doi.org/10.1016/S0967-0645(01)00088-1, 2001. 4. Bates, S. S., Beach, D. G., Comeau, L. A., Haigh, N., Lewis, N. I., Locke, A., Martin, J. L., McCarron, P., McKenzie, C. H., Michel, C., Miles, C. O., Poulin, M., Quilliam, M. A., Rourke, W. A., Scarratt, M. G., Starr, M., and Wells, T.: Marine Harmful Algal Blooms and Phycotoxins of Concern to Canada, Canadian Technical Report of Fisheries and Aquatic Sciences, Open File 3384, 322 pp., ISBN 978-0-660-35266-4, 2020. 5. Bérard-Therriault, L., Poulin, M., and Bossé, L.: Guide d'identification du phytoplancton marin de l'estuaire et du golfe du Saint-Laurent: Incluant également certains protozoaires, Publication spéciale canadienne des sciences halieutiques et aquatiques, 128, 387 p., ISBN 0-660-96057-5, 1999.
|
|