General comments:

1) We thank the reviewer for their positive comments and for contributing to improving the manuscript. Your comments have been considered in the revised version.

Specific comments:

1) We have added both 2014 and 2015 to the references, thank you.

2) We corrected the reference, thank you.

3) In our study, primary production proxies at the Pointe-des-Monts site include chloropigments, diatoms and dinoflagellates. To avoid confusion, we have clarified this sentence in the revised version of the manuscript, which now reads “[…], but we note no correlation to other primary production proxies (i.e., fluxes of chloropigments, diatoms and dinoflagellates).”

4) We have changed the * symbol to [].

Major comments:

1) Trap depths were determined based on several considerations:

• All traps were located within the deep layer.
• The sediment traps PDM-224 and BC-133 were located 58 and 67 m above seafloor, respectively, which is well above the benthic nepheloid layer (i.e., layer of water above the seafloor that contains significant amounts of suspended sediment), which is estimated to be about 10 m above the seafloor in our study area (Bourgault et al., 2014; Casse et al., 2019).
• In the main canyon system, the ADCP was located 27 m above the seafloor (156 m water depth) to be consistent with to methodology used in Normandeau et al. (2020). The PDM-154 sediment trap was placed at a similar water depth to the ADCP.
• BC-133 was located at a comparable distance above seafloor as PDM-224 while also being at a comparable depth below the surface as PDM-154.

To clarify this point, in the revised version of the manuscript we have added:

Lines 109-110: “Traps BC-133 and PDM-224 were positioned 67 m and 58 m above seafloor, respectively, above the estimated benthic nepheloid layer (i.e., <250 m of water depth; Bourgault et al., 2014; Casse et al., 2019).”

Bourgault, D., Morsilli, M., Richards, C., Neumeier, U., and Kelley, D. E.: Sediment resuspension and nepheloid layers induced by long internal solitary waves shoaling orthogonally on uniform slopes, Continental Shelf Research, 72, 21-33. http://dx.doi.org/10.1016/j.csr.2013.10.019, 2014.

Casse, M., Montero-Serrano, J.-C., St-Onge, G., and Poirier, A.: REE distribution and Nd isotope composition of estuarine waters and bulk sediment leachates tracing lithogenic inputs in eastern Canada, Marine Chemistry, 211, 117-130. https://doi.org/10.1016/j.marchem.2019.03.012, 2019.

2) The sediment traps BC-133 and PDM-154 are within the deep layer and temperature and salinity fluctuations are not directly associated with surface conditions. A decrease in water temperature and salinity at these depths could be due to:

• A greater contribution of waters from the Labrador Current (lower temperatures and salinities) than from the North Atlantic waters (higher temperatures and salinities).
• Vertical mixing of the cold intermediate layer (lower temperatures and salinities) with the deep layer (higher temperatures and salinities).

However, with the data collected as part of the present study, we cannot determine the cause of the decrease in water temperature and salinity in December 2020.

3) Normandeau et al. (2020) reported that the large turbidity currents that occur every 2-3 years were initiated during storms that exhibited sustained (>7 h) high windspeeds (>60 km h^-1), which caused large storm waves. At or near low tide, these storm waves subsequently triggered a turbidity current. In the context of global climate warming, it can be expected that a shortening of the sea ice season and increased storm frequency may favor the development of turbidity currents.

4) We thank the reviewer for raising this important point and have added in the revised version of the manuscript a brief explanation at the beginning of section 5.3 to address this:

“The sinking rate of biogenic matter is highly variable depending on shape, size, density, aggregation, remineralization, etc. For example, sinking rates of individual diatoms range from 0.1 to 10 m d^-1 (Smayda, 1970) while aggregates can sink at rates of 88 to 569 m d^-1 (Iversen et al., 2010). Sinking biogenic matter generally form aggregates (“marine snow”) to facilitate vertical fluxes of pelagic particles, therefore, we can assume that the sinking particles obtained in the sediment traps are representative of their respective sampling time periods.”

Iversen, M. H., Norwald, N., Ploug, H., Jackson, G. A., and Fischer, G.: High resolution profiles of vertical particulate organic matter export off Cape Blanc, Mauritania: Degradation processes and ballasting effects, Deep-Sea Research I, 57, 771–784, doi:10.1016/j.dsr.2010.03.007, 2010.

Smayda, T.: The suspension and sinking of phytoplankton in the sea, Oceanography Marine Bulletin, 8, 353–414, 1970.

5) Diatoms are the most abundant phytoplankton in the Lower St. Lawrence Estuary and almost all diatom taxa are autotrophic, whereas dinoflagellates are the second most abundant phytoplankton and approximately half the dinoflagellate taxa are heterotrophic (micrograzers). Diatoms bloom first due to higher growth rates, lower light requirements (particularly for pennate diatoms which bloom before centric diatoms), and higher nutrient requirements, particularly nitrate and dissolved silicon. The diatom bloom will end when the surface mixed layer becomes limited in nutrients and dinoflagellates will then bloom because the heterotrophic taxa are able to feed on diatoms and other primary producers. We very briefly mention this pattern in the second paragraph of section 5.3. This has been well established in the region therefore we do not believe it is necessary to explain in depth in our manuscript. 

6) We thank the reviewer for raising this point. The mixed layer deepens from fall into winter and then becomes shallower again in the spring. In lines 386-390, our intention was not to address the question of why primary production is lower in the winter, but rather to evaluate if resuspension events could affect the surface mixed layer when primary production would be more impacted. We have rephrased this in the revised manuscript (lines 393-397) to increase clarity:

“However, our data do not permit to evaluate if lofted sediments also reached the surface layer where they would have decreased primary production. Additionally, turbidity currents and other sediment remobilization events appear to be more frequent from late fall through winter, therefore we cannot determine if sediment lofting would play a key role in this system throughout the entire year, particularly from late spring through early fall, when primary production is greatest.”

7) Only about 20% of total dinoflagellate taxa are known to produce organic resting cysts. Of the 16 motile dinoflagellate taxa observed in our study, four are currently known to produce resting cysts: Pentapharsodinium dalei, Protoperidinium americanum, Protoperidinium conicum, and Protoperidinium spp. In the present study, we observed cysts of the last three taxa but did not observe cysts of P. dalei, which we know are abundant in the regional surface sediments. We do not believe that preservation is an issue because other sediment trap studies using formalin as a preservative have observed cysts of P. dalei (e.g., Heikkilä et al., 2016). It is possible that we did not observe cysts of P. dalei because they were outnumbered by other dominant taxa (below detection).  

Heikkilä, M., Pospelova, V., Forest, A., Stern, G. A., Fortier, L., and Macdonald, R. W.: Dinoflagellate cyst production over an annual cycle in seasonally ice-covered Hudson Bay, Marine Micropaleontology, 125, 1-24, http://dx.doi.org/10.1016/j.marmicro.2016.02.005, 2016.

General comments:

1) We thank the reviewer for their positive comments and for contributing to improving the manuscript. Your comments have been considered in the revised version. 

Specific comments:

1) We have clarified this in the revised version of the manuscript, which now reads “To identify canyon-specific processes, a sediment trap was also deployed offshore Baie-Comeau (BC), a site not affected by canyon-related sediment remobilization events, to contrast with biogenic matter export in the LSLE (Fig. 1c).”

2) We corrected the sentence, thank you.

3) We have removed “slightly” so the sentence now reads “Overall, fluxes of chloropigments exhibit similar patterns at both depths, with higher flux values at PDM-224.”

4) We corrected the sentence, thank you.

5) We thank the reviewer for raising this point. In addition to the size of the canyon system, there are other factors that need to be considered.

Large submarine canyon systems are not located within estuaries, which are typically rich in nutrients. In the Lower St. Lawrence Estuary (LSLE), upwelling of nutrient-rich waters at the head of the Laurentian Channel, subsequent mixing in the surface layer, and strong estuarine circulation provide an important supply and distribution of nutrients year-round. Freshwater inputs from the Saguenay, Outardes, Manicouagan, and St. Lawrence rivers additionally introduce nutrients to the system. Light is therefore the most important variable controlling phytoplankton growth in the LSLE (Therriault & Levasseur, 1985).

Globally, there are many triggers for turbidity currents, which are almost always triggered in canyon systems with important sediment supply from rivers of longshore drift; thus the “sediment-starved” canyon system at Pointe-des-Monts is an exception (Normandeau et al., 2017 and references therein). The sediment supply and trigger influence the frequency, seasonality, and amplitude of turbidity currents, which will ultimately determine the impact of these events on regional productivity.

The results presented here do not allow to determine the different impacts of small and large submarine canyon systems, but rather provide insight into a singular annual cycle for a small submarine canyon system in the LSLE.

6) We have included the annual fluxes of chloropigments and particulate organic carbon measured in the present study to increase clarity and highlight that they are much greater than those measured in Genin et al. (2021), as well as included the trap and water-column depths. Lines 432 to 434 of the revised manuscript now read: “Annual chloropigment (70 to 120 mg m^-2 yr^-1) and POC (11 to 19 g m^-2 yr^-1) fluxes measured here were much greater than those measured near Cabot Strait (35 mg m^-2 yr^-1 and 1.1 g m^-2 yr^-1, respectively; 100 m trap depth, 461 m water-column depth; Genin et al., 2021)”. We would like to avoid including a table with the values, as this section is not a focus of the study, but rather a brief discussion of previous sediment trap studies to provide a regional context to our values.