Abstract
Harmful algal blooms (HABs) caused by the toxigenic dinoflagellate Alexandrium catenella recur regularly in the Lower St. Lawrence Estuary (LSLE, eastern Canada). A quantitative polymerase chain reaction (qPCR) assay detects A. catenella DNA which may originate from cysts, cells, or extracellular DNA. Here, A. catenella DNA is used as a proxy for cyst presence in the Pointe-des-Monts canyon system. We show that resting cysts are concentrated in nearshore sediments and on the canyon fan, but are depleted along the canyon axis. Sediment traps reveal that major cyst resuspensions occur exclusively during winter storms under ice-free conditions, with peaks in A. catenella DNA fluxes coinciding with turbidity currents and high total particulate matter export. These events effectively flush coastal cysts offshore, creating a negative feedback loop that reduces subsequent local bloom potential. Conversely, climate change-driven increases in summer-to-autumn storm frequency and intensity could resuspend cysts under optimal proliferation conditions. Sedimentary ancient DNA in a 210Pb-dated sediment core also demonstrates that qPCR reliably records known historical A. catenella bloom events. These results highlight the critical, yet underappreciated, role of submarine canyon systems and storm-driven sediment dynamics in modulating A. catenella bloom risks, and suggest that ongoing climate-driven shifts in sea-ice cover and storm seasonality are likely to influence future HABs in the LSLE and similar high-latitude systems.
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Acknowledgements
This study was supported jointly by Réseau Québec maritime and the Marine Environmental Observation Prediction and Response Network. This study received further support from the Natural Sciences and Engineering Research Council of Canada through Discovery Grants awarded to J.-C.M.-S., A.L., G.S., E.M.B., A.R., and M.G., and from FQRNT research clusters Geotop and Québec-Océan to F.J. The acquisition of the wave data at Saint-Ulric was funded by the Government of Quebec (Ministère des Transports et de la Mobilité durable). We thank Geotop for the scholarship to F.J. and the International Association of Sedimentologists (IAS) for the postgraduate research Grant awarded to F.J. that allowed 210Pb analysis. We thank Donald M. Anderson for providing an A. catenella culture sample.
Funding
This study is part of the research program ″Monitoring natural hazards during coastal to offshore sediment remobilization and its impacts on primary productivity dynamics in the Lower St. Lawrence Estuary″ which received joint funding from Réseau Québec maritime (RQM) and the Marine Environmental Observation Prediction and Response Network (MEOPAR). This study also received further support from the Natural Sciences and Engineering Research Council of Canada through Discovery Grants awarded to J.C.M.S., A.L., G.S., E.M.B., A.R., and M.G., and from the FRQNT research clusters Geotop (https://doi.org/10.69777/377326) and Québec-Océan (https://doi.org/10.69777/309012).
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Jacques, F., Limoges, A., Gosselin, M. et al. Winter sediment resuspension in a submarine canyon drives the offshore export of toxigenic Alexandrium catenella cysts.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-65036-z
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DOI: https://doi.org/10.1038/s41598-026-65036-z
Keywords
Alexandrium catenella
- Dinoflagellate cyst resuspension
- Harmful Algal Blooms
- qPCR
- Sedimentary ancient DNA
- Sediment dynamics
- Particulate matter export
- Sediment traps
- Submarine canyons
Source: Ecology - nature.com
