the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 23 Feb 2026
Impacts of ridge-induced upwelling on the biological carbon pump in the tropical Northwestern Pacific
Abstract. Submarine ridges are prominent topographic features in the global ocean, yet their role in regulating the biological carbon pump remains underexplored. In this study, we investigated the spatial variability of phytoplankton production, particle dynamics, and carbon export along a meridional transect in the tropical Northwestern Pacific, spanning a warm eddy (WE), a cold eddy (CE), and the Kyushu-Palau Ridge (KPR). A suite of in situ measurements, including 14C-based primary production, HPLC pigment analysis, and particle profiling via Underwater Vision Profiler (UVP5-HD), was used to assess regional differences in biological carbon pump processes. Marked thermocline shoaling and nutrient uplift were observed in both the CE and KPR regions, but the KPR-derived upwelling waters had higher nutrient concentrations, resulting in the highest nutrient inventories in the upper 200 m and supporting elevated primary production (142.05 mg C m-2 d-1) and phytoplankton biomass there. Correspondingly, the KPR region exhibited the highest particle volume concentrations in the upper 200 m, followed by the CE, with the WE and background regions showing the lowest values. The 0–2000 m water column in the KPR region was also characterized by a substantially greater contribution of large particles (ESD ≥ 500 μm), which in turn supported enhanced particulate organic carbon (POC) export in this area. POC fluxes in the KPR region reached 9.04 ± 6.74, 5.52 ± 0.10, and 3.09 ± 1.96 mg C m-2 d-1 at 200 m, 1000 m, and 2000 m, respectively, which were 2.8 to 5.7 times higher than those in the CE region and 5.9 to 11.4 times higher than in the background region. Consistently, export efficiency (e-ratio) peaked in the KPR region (10 %), exceeding those in the CE (3 %), WE (3 %), and background (5 %) regions. Using the KPR as a representative case, our results highlight the critical role of ridge-induced upwelling in regulating phytoplankton production and particle dynamics, as well as enhancing biological carbon export and surface–deep coupling in oligotrophic oceans. These findings underscore the importance of incorporating such topographic processes into global oceanic carbon cycle research.
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RC1: 'Comment on egusphere-2026-597', Anonymous Referee #1, 16 Jun 2026
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AC1: 'Reply on RC1', Shujin Guo, 08 Aug 2026
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Dear reviewer,
Thank you very much for your valuable suggestions. Your comments have been extremely helpful, and we have done our best to revise the manuscript accordingly. We hope that the revised version meets your expectations. The following is a detailed account of the specific revisions.
General comments
This is an important contribution showing the impact of oceanic topographic features on POC fluxes, as these are often overlooked in flux assessments. However, there are substantial methodological considerations that I detail below.
Response: We thank the reviewer for the positive evaluation of our work and for recognizing the importance of investigating the influence of oceanic topographic features on POC fluxes. We also appreciate the reviewer’s thoughtful comments regarding the methodological aspects of the study. We have carefully considered all concerns and revised the manuscript accordingly. Detailed responses are provided below.
L32. It is unclear what you mean by background regions.
Response: Thank you for pointing out this ambiguity. In this study, the background region refers to the stations located between the warm eddy and the cold eddy, where no pronounced mesoscale eddy or direct topographic influence of the Ridge was identified. We have now clarified this definition in the manuscript and changed “background regions” to the singular form “background region (BR).”
L57-61. These few sentences could be streamlined.
Response: We agree with the comment that these sentences were somewhat repetitive. We have condensed them into a single sentence to improve clarity and conciseness. The revised version is as follow: “Furthermore, episodic and sustained fluxes of sinking biogenic particles deliver organic carbon to the deep ocean and support benthic food webs, highlighting the importance of the BCP for deep-sea ecosystem functioning (Dunlop et al., 2016; Rodil et al., 2020; Iversen, 2023; Ramondenc et al., 2025).”
L63. Could you here mention a depth horizon to measure the efficiency of the BCP?
Response: Thanks for the helpful suggestion. We agree that BCP efficiency should be defined relative to specific depth horizons. We have revised the Introduction to clarify that export efficiency is generally evaluated across an upper-ocean reference depth near the base of the euphotic zone (Shih et al., 2015; Seo et al., 2022).
Shih, Y. Y., Hung, C. C., Gong, G. C., Chung, W. C., Wang, Y. H., Lee, I. H., Chen, K. S., Ho, C. Y.: Enhanced particulate organic carbon export at eddy edges in the oligotrophic Western North Pacific Ocean. Plos One, 10(7), e0131538, https://doi.org/10.1371/journal.pone.0131538, 2015.
Seo, J., Kim, G., Park, J. H., Seo, H., Na, T., Kang, S. K., Hwang, J.: Export of particulate organic carbon (POC) in the eddy region of the tropical northwest Pacific. Frontiers in Marine Science, 9, 976201, https://doi.org/10.3389/fmars.2022.976201, 2022.
L85. “The strength of the BCP” has not been defined.
Response: Thank you for this comment. We agree that the phrase “the strength of the BCP” was ambiguous. We have replaced it with the more specific terms “POC export flux and transfer efficiency,” which directly describe the magnitude and efficiency of POC transport to depth. The original sentence was revised to “While it is well established that physical dynamics and water mass circulation influence POC export flux and transfer efficiency, the potential effects of ridge-induced upwelling on these processes remain largely unknown.”
L135. Please correct to UVP5.
Response: Thank you for pointing this out. We have corrected “UVP 5.0” to “UVP5” in the manuscript.
L142. There should be a DOI associated with the product.
Response: Thanks for this comment. We have added the DOI of the Copernicus Marine Service product to the revised manuscript.
L149. D3 seems to be at the edge of the eddy. Why did you choose to include it in BR rather than WE?
Response: Thank you for raising this important point. Although station D3 was geographically close to the western warm eddy (WE), our regional classification was not based solely on the distance between a station and the apparent eddy center. Instead, the eddy boundary was identified primarily from the outermost closed positive sea-level anomaly (SLA) contour on the sampling date, together with the corresponding in situ hydrographic and biogeochemical characteristics. The use of closed SLA contours to delineate mesoscale eddy boundaries is widely adopted in altimetry-based eddy identification because these contours provide an approximation of the coherent geostrophic circulation associated with an eddy (Chelton et al., 2011; Chaigneau et al., 2011). Station D3 was located close to, but outside, the outermost closed positive SLA contour associated with the WE. Moreover, its vertical hydrographic structure and biogeochemical properties did not exhibit the pronounced eddy-core signature observed at D1 and were generally more comparable to those of the intervening background waters. We therefore assigned D3 to the background region (BR) rather than to the WE.
Nevertheless, we agree that D3 was situated near the eddy periphery and may have been influenced to some extent by peripheral eddy circulation or exchange between the eddy and surrounding waters. Its classification as BR should therefore not be interpreted as implying a complete absence of eddy influence, but rather that it was outside the objectively defined eddy boundary and lacked a clear eddy-core signature. Thanks for the comment again.
Chaigneau A, Texier M L, Eldin G, et al. 2011. Vertical structure of mesoscale eddies in the eastern South Pacific Ocean: A composite analysis from altimetry and Argo profiling floats. Journal of Geophysical Research, 116: C11025.
Chelton D B, Schlax M G, Samelson R M. 2011. Global observations of nonlinear mesoscale eddies. Progress in Oceanography, 91: 167-216.
L174. By samples, do you mean filters or filtrates?
Response: Thanks for pointing out this ambiguity. Here, “samples” refers to the filtrates rather than the filters. We have revised the sentence accordingly.
L224-225. Why not use Zooprocess? Will the custom scripts be made available?
Response: Thanks for this comment. We did not use ZooProcess because the UVP images in this study were processed using an instrument-specific image-processing pipeline that had been developed and calibrated for our UVP configuration and raw image format. The custom scripts performed the same essential steps required for particle analysis, including image calibration, particle segmentation, removal of edge objects and obvious artifacts, extraction of particle projected area, and conversion from pixel dimensions to metric units based on tank calibration. The same processing parameters were applied consistently to all profiles, ensuring internal consistency among stations. We agree that the description of the image-processing procedure was insufficient in the original manuscript. We have therefore revised the Methods section to provide more details on the main processing steps and calibration procedure. The scripts used for particle detection and size calculation will be made available upon reasonable request.
L225. Please change equivalent spherical diameter to equivalent circular diameter throughout the manuscript.
Response: We thank the reviewer for pointing out this. We have replaced “equivalent spherical diameter (ESD)” with “equivalent circular diameter (ECD)” throughout the manuscript.
L263. This set of parameters may not be adequate for your study area. If you want to use globally estimated parameters, then you could also consider the parameters determined in Clements et al. 2023 (https://doi.org/10.1029%2F2022GB007633). I suggest using several sets of parameters from the literature so to see how it may impact your flux estimates. Or the use of this particular set of coefficients and how it may impact your results should at least be discussed.
Response: We thank the reviewer for this valuable suggestion. We agree that the conversion of UVP-derived particle size distributions into POC flux is sensitive to the empirical coefficients used and that globally derived coefficients may not fully represent particle characteristics in the tropical northwestern Pacific. In this study, we retained the coefficients of Guidi et al. (2008a) because they were derived from joint analyses of UVP-derived particle size distributions and independently measured sediment-trap carbon fluxes and have subsequently been applied across a range of marine environments, including the tropical western Pacific (Iversen et al., 2010; Ramondenc et al., 2016; Wang et al., 2024a, b). Retaining this parameterization also facilitates comparison with previous UVP-based studies.
Nevertheless, we acknowledge that the exponent adopted from Guidi et al. (2008a) differs from the globally optimized value reported by Clements et al. (2023). This difference highlights the uncertainty associated with converting particle size distributions into POC flux and suggests that the absolute flux estimates may depend on the selected parameterization. Because the same coefficients were applied consistently to all stations, the resulting flux estimates provide an internally consistent basis for comparing spatial and vertical patterns. We therefore expect the broad station-to-station patterns to be less sensitive than the absolute flux values to the choice of coefficients. We have added a discussion of this methodological uncertainty to the revised manuscript and now emphasize that the absolute POC flux estimates should be interpreted with caution. We have also clarified that the use of a single parameter set assumes uniform relationships among particle size, carbon content, and sinking velocity across stations, although these relationships may vary with particle type, composition, porosity, and environmental conditions.
Iversen, M. H., Nowald, N., Ploug, H., Jackson, G. A., Fischer, G.: High resolution profiles of vertical particulate organic matter export off Cape Blanc, Mauritania: degradation processes and ballasting effects. Deep-Sea Res. PT I, 57(6), 771–784, https://doi.org/10.1016/j.dsr.2010.03.007, 2010.
Ramondenc, S., Madeleine, G., Lombard, F., Santinelli, C., Stemmann, L., Gorsky, G., Guidi, L.: An initial carbon export assessment in the Mediterranean Sea based on drifting sediment traps and the underwater vision profiler data sets. Deep-Sea Res. PT I, 117, 107–119, https://doi.org/10.1016/j.dsr.2016.08.015, 2016.
Wang, X. Y., Li, H. L., Zhang, J. J., Chen, J. F., Xie, X. H., Xie, W., Yin, K. D., Zhang, D. S., Ruiz-Pino, D., Kao, S. J.: Seamounts generate efficient active transport loops to nourish the twilight ecosystem. Sci. Adv., 10(26), eadk6833, 10.1126/sciadv.adk68, 2024a.
Wang, Z. Y., Fang, C., Yang, C. H., Zhang, G. Y., Sun, D.: Latitudinal gradient and influencing factors of deep-sea particle export along the Kyushu-Palau Ridge in the Philippine Sea. Sci. Total Environ., 906, 167460, https://doi.org/10.1016/j.scitotenv.2023.167460, 2024b.
L269. Why do you use the UVP flux at 150 m and not at the base of the euphotic zone?
Response: We thank the reviewer for this important comment. We used the POC flux at 150 m as a common reference horizon because 150 m was below the euphotic zone at all four stations and allowed direct comparison among stations with different euphotic-zone depths. The use of a fixed 150 m horizon is also consistent with previous studies in which export efficiency was calculated from POC flux at 150 m relative to integrated primary production (e.g., Buesseler et al., 2010; Ceballos-Romero et al., 2016; Karl et al., 2021; Yoon et al., 2022). We acknowledge that some attenuation may occur between the base of the euphotic zone and 150 m; therefore, our e-ratio specifically represents the fraction of euphotic-zone primary production reaching 150 m rather than the fraction exported immediately below the euphotic zone. We have revised accordingly in the manuscript.
Buesseler K O, McDonnell A M P, Schofield O M E, Steinberg D K, Ducklow H W. 2010. High particle export over the continental shelf of the west Antarctic Peninsula. Geophysical Research Letters, 37: L22606.
Ceballos-Romero E, Moigne F A C, Henson S, et al. 2016. Influence of bloom dynamics on particle export efficiency in the North Atlantic: a comparative study of radioanalytical techniques and sediment traps. Marine Chemistry, 186: 198-210.
Karl D M, Letelier R M, Bidigare R R, et al. 2021. Seasonal-to-decadal scale variability in primary production and particulate matter export at Station ALOHA. Progress in Oceanography, 195: 102563.
Yoon J E, Kim J H, Kim I N. 2022. Climate-driven high primary production and contrasting export production in the eastern North Pacific Subtropical Gyre. Frontiers in Marine Science, 8: 710540.
L292-293. How does that tell you that the water column is stratified? What is the temperature below?
Response: Thanks for this comment. We have revised the paragraph to explicitly describe the vertical temperature gradient. Temperatures exceeded 27.5 ℃ in the upper 50 m but decreased rapidly below this layer, reaching approximately 20–25 ℃ at 100 m and 10–20 ℃ at 200 m. This pronounced vertical temperature gradient indicates strong upper-ocean stratification.
Figure 2. It could be useful to display the MLD on the figures. It is also really hard to read salinity values on the upper right plot.
Response: Thanks for this comment. We have added the MLD in the revised Fig. 2a. The blue dots indicate the station-specific MLD values, and the black dashed line connects these values along the transect. We also adjusted the salinity contour labels to improve their readability. The blank areas near the surface at several stations represent salinity data that were excluded during quality control, rather than a plotting error, and this has now been clarified in the figure caption.
L332. Are you referring to integrated values? Can you also say in the method how you integrate nutrient concentrations over the water column?
Response: Thanks for the comment. Yes, here we refer to the nutrient concentrations integrated over the upper 200 m. We have revised this sentence and added the integration method to the Methods section. Nutrient inventories were calculated from the discrete concentration profiles using trapezoidal integration between adjacent sampling depths.
L353-359. What is the confidence in determining phytoplankton groups?
Response: Thanks for the comment. Phytoplankton-group contributions were estimated from HPLC pigment concentrations using CHEMTAX. Therefore, the results should be regarded as pigment-based, semi-quantitative estimates of major phytoplankton functional groups rather than definitive taxonomic identifications. The confidence is generally higher for groups characterized by relatively distinctive diagnostic pigments, whereas uncertainty may occur for groups that share pigments of exhibit variable pigment-to-Chl a ratios due to photoacclimation and physiological status. We have clarified these limitations in the Methods section and revised the Results to avoid overly definitive wording.
Figure 4. What does “Haptophytes-6” mean?
Response: Thank you for this comment. “Haptophytes-6” referred to the haptophyte type used in the CHEMTAX input matrix. Because only one haptophyte group was included in our analysis, we have simplified the term to “Haptophytes” throughout the manuscript and in Fig. 4.
L385. Would it be relevant to also compare this with attenuation here?
Response: Thanks for this comment. We agree that attenuation is more directly relevant to sinking POC flux rather than to PVC inventories. Because PVC represents particle stock rather than particle flux, we did not calculate an attenuation coefficient from the depth-integrated PVC values in this section. Instead, we have added POC flux transfer efficiency in Section 3.4, where UVP-derived POC fluxes are presented. In the revised manuscript, the PVC correlations are interpreted as evidence of vertical connectivity in particle stocks, whereas the transfer efficiency of POC flux are used to evaluate the efficiency of downward particle transfer.
L407. It would be interesting to compare metrics between stations, such as the attenuation coefficient or the transfer efficiency.
Response: We thank the reviewer for this helpful suggestion. In the revised manuscript, we calculated the POC transfer efficiency from 150 to 2000 m, because this metric can be directly derived from the UVP-based flux estimates and allows straightforward comparison among stations. The transfer efficiency has now been added to Table 2. Across the transect, transfer efficiency ranged from 21% to 51%, indicating substantial spatial variability in the attenuation of sinking POC flux. The highest transfer efficiency was observed at D7 (51%), followed by D8 (44%), D9 (37%), and D12 (36%), whereas lower values occurred at D3 (21%) and D4 (22%). Although D7 showed the highest proportional transfer efficiency, its absolute POC fluxes were much lower than those at D12. In contrast, D12 combined the highest e-ratio, strongly elevated upper-ocean POC flux, and relatively high transfer efficiency, resulting in the highest POC flux at 2000 m. We have revised the Results and Discussion sections accordingly.
L424. “POC flux was significantly positively correlated with PVC” since it is estimated from particle size distribution, this is expected. This is a spurious correlation.
Response: We thank the reviewer for pointing this out. We agree that the positive correlation between UVP-derived POC flux and PVC is not statistically independent. We have therefore removed this correlation from the interpretation. In the revised manuscript, we focus instead on correlations with variables that are more independent of the flux calculation. The text has been revised accordingly.
Figure 8. You show many correlations that you don’t mention in the text. I would also suggest to not show correlation values if not significant. It would be interesting however to compare nutrient concentration to the metrics mentioned above, or to also relate them to fluxes below. This figure also needs to be described more in depth or removed. Right now this looks like a lot of information and it is hard to extract a clear message from it. For example, is it useful to have the correlation of POC fluxes with depth or salinity?
Response: Thanks for this constructive comment. We agree that the original Fig. 8 contained too many correlations, including several variables that were not central to the interpretation. In response, we have removed the original Fig. 8. Instead, we added a new Table 3 to present a more focused Pearson correlation analysis. The revised analysis compares the main carbon export metrics, including POC fluxes at 200, 1000, and 2000 m and transfer efficiency, with selected upper 200 m environmental and particle variables. These variables include integrated DIN, phosphate, silicate, Chl (a), and PVC over the upper 200 m, as well as the mean fractions of small- and large-particle PVC over the same depth interval. Correlations with depth and salinity were removed because they did not provide a clear mechanistic message for the present study. Following the reviewer’s suggestion, we also examined the relationships between nutrient inventories and deeper POC fluxes. The revised results show that POC flux at 1000 m was significantly positively correlated with integrated DIN, phosphate, silicate, and PVC in the upper 200 m. POC fluxes at 200 and 2000 m were significantly correlated with integrated PVC and the mean fractions of small- and large-particle PVC. The Results and Discussion sections have also been revised accordingly.
L551-553. Is there literature data for the area about grazing rates?
Response: Thanks for the comment. To our knowledge, direct measurements of zooplankton grazing rates are not currently available for the study area of this manuscript. We have therefore searched relevant observations from comparable tropical Pacific open-ocean environments. In the equatorial Pacific, Landry et al. (2011) found that microzooplankton and mesozooplankton grazing accounted for approximately 70% and 30%, respectively, of euphotic phytoplankton growth. In the oligotrophic western tropical South Pacific, Carlotti et al. (2018) estimated that mesozooplankton grazing removed 19%-184% of daily primary production and that fecal pellet production ranged from 31 to 128 mg C m-2 d-1 at three long-duration stations. These studies demonstrate that zooplankton grazing and fecal pellet production can represent important pathways of carbon transfer in tropical Pacific waters. However, because our study measured zooplankton abundance rather than grazing or fecal pellet production rates, we agree that the original statement was too definitive. We have revised the text to describe enhanced grazing and fecal-pellet production at station D12 as a potential mechanism rather than a directly demonstrated process.
Landry M R, Selph K F, Taylor A G, et al. 2011. Phytoplankton growth, grazing and production balances in the HNLC equatorial Pacific. Deep-Sea Research II, 58: 524-535.
Carlotti F, Pagano M, Guilloux L, et al. 2018. Meso-zooplankton structure and functioning in the western tropical South Pacific along the 20th parallel south during the OUTPACE survey (February-April 2015). Biogeosciences, 15: 7273-7297.
L530-532. Could it also be due to lateral transport along the ridge?
Response: Thanks for this insightful comment. We agree that lateral transport associated with topographically steered currents along the ridge could also contribute to the observed correlations in particle distributions among successive depth layers. Because our present dataset does not include direct current measurements or particle-tracking observations, we cannot distinguish or quantify the relative contributions of vertical settling and lateral advection. The correlations were intended to indicate strong connectivity of particle distributions throughout the water column, with gravitational settling representing one plausible mechanism rather than excluding lateral transport. We will specifically address this issue in future studies by combining particle observations with direct current measurements and particle-transport analyses. Thanks again for this comment.
L532-533. Here the transfer efficiency would be useful to support this statement.
Response: Thanks for the helpful suggestion. We calculated the POC transfer efficiency as the ratio of the estimated POC flux at 2000 m to that at 150 m. The transfer efficiency ranged from 21% to 51% among stations, with an overall mean of 34±10%. At the KPR stations, the transfer efficiency was 29% at D11 and 36% at D12. These results indicate that a substantial fraction of the POC flux in the upper ocean was retained at 2000 m and provide quantitative support for the vertical transfer of particulate carbon to the deep ocean. We have revised the manuscript accordingly. Thanks for the comment again.
L542-546. Can you relate that to phytoplankton community structure? What type of particles do we expect? Here a bit of literature regarding the role of the dominant phytoplankton groups in promoting export would be useful.
Response: Thanks for this helpful suggestion. We have expanded the discussion to relate the observed increase in large particles to the phytoplankton community structure. The CHEMTAX results indicated that the phytoplankton community in the KPR region was dominated largely by small phytoplankton groups, particularly prochlorophytes and haptophytes. Because these pico- and nanophytoplankton cells are much smaller than the large-particle category identified by the UVP, the observed large particles were unlikely to be individual phytoplankton cells. Instead, they most likely represented phytodetrital aggregates, marine snow, and zooplankton-derived fecal material formed through the aggregation and trophic repackaging of small phytoplankton.
Previous studies have demonstrated that small phytoplankton, despite their low individual sinking velocities, can contribute substantially to carbon export through several indirect pathways. Pico- and nanophytoplankton cells can become incorporated into larger organic aggregates through physical coagulation and association with extracellular polymeric substances. They can also be consumed by zooplankton and repackaged into larger, denser, and more rapidly sinking fecal pellets. These processes effectively increase the size and sinking velocity of particles derived from small phytoplankton and reduce their residence time in the upper ocean (Richardson, 2019). Therefore, an assemblage dominated by small phytoplankton does not necessarily imply weak particle export, particularly when aggregation and trophic repackaging are active. The occurrence of nano- and picoplankton pigments in particles larger than 53 μm provides direct evidence that small phytoplankton can become incorporated into larger sinking aggregates (Mackinson et al., 2015). In the tropical western Pacific, pigmented nano-sized eukaryotes, with haptophytes as a dominant group, have been detected at depths of up to 5000 m and were proposed to be transported downward through phytodetritus, aggregates, and fecal pellets (Xu et al., 2018). These findings suggest that the prochlorophyte- and haptophyte-dominated assemblage could contribute to the formation of large sinking particles through aggregation and food-web processing. We have added this interpretation to the revised manuscript. However, because the UVP measurements provide information on particle size and abundance but not particle composition, the identities and biological origins of the large particles are presented as plausible rather than directly confirmed.
Mackinson B L, Moran S B, Lomas M W, et al. 2015. Estimates of micro-, nano-, and picoplankton contributions to particle export in the northeast Pacific. Biogeosciences, 12: 3429-3446.
Xu D P, Sun P, Zhang Y Z, et al. 2018. Pigmented microbial eukaryotes fuel the deep sea carbon pool in the tropical Western Pacific Ocean. Environmental Microbiology, 20(10): 3811-3824.
Richardson T L. 2019. Mechanisms and pathways of small-phytoplankton export from the surface ocean. Annual Review of Marine Science, 11: 57-74.
Once again, thank you very much for your valuable comments. We sincerely hope that our responses and revisions meet your expectations.Best regards,
Shujin Guo
Citation: https://doi.org/10.5194/egusphere-2026-597-AC1
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AC1: 'Reply on RC1', Shujin Guo, 08 Aug 2026
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Review of Impacts of ridge-induced upwelling on the biological carbon pump in the tropical Northwestern Pacific by Guo et al.
General comments
This is an important contribution showing the impact of oceanic topographic features on POC fluxes, as these are often overlooked in flux assessments. However, there are substantial methodological considerations that I detail below.
Detailed comments
L32. It is unclear what you mean by background regions.
L57-61. These few sentences could be streamlined.
L63. Could you here mention a depth horizon to measure the efficiency of the BCP?
L85. “The strength of the BCP” has not been defined.
L135. Please correct to UVP5.
L142. There should be a DOI associated with the product.
L149. D3 seems to be at the edge of the eddy. Why did you choose to include it in BR rather than WE?
L174. By samples, do you mean filters or filtrates?
L224-225. Why not use Zooprocess? Will the custom scripts be made available?
L225. Please change equivalent spherical diameter to equivalent circular diameter throughout the manuscript.
L263. This set of parameters may not be adequate for your study area. If you want to use globally estimated parameters, then you could also consider the parameters determined in Clements et al. 2023 (https://doi.org/10.1029%2F2022GB007633). I suggest using several sets of parameters from the literature so to see how it may impact your flux estimates. Or the use of this particular set of coefficients and how it may impact your results should at least be discussed.
L269. Why do you use the UVP flux at 150 m and not at the base of the euphotic zone?
L292-293. How does that tell you that the water column is stratified? What is the temperature below?
Figure 2. It could be useful to display the MLD on the figures. It is also really hard to read salinity values on the upper right plot.
L332. Are you referring to integrated values? Can you also say in the method how you integrate nutrient concentrations over the water column?
L353-359. What is the confidence in determining phytoplankton groups?
Figure 4. What does “Haptophytes-6” mean?
L385. Would it be relevant to also compare this with attenuation here?
L407. It would be interesting to compare metrics between stations, such as the attenuation coefficient or the transfer efficiency.
L424. “POC flux was significantly positively correlated with PVC” since it is estimated from particle size distribution, this is expected. This is a spurious correlation.
Figure 8. You show many correlations that you don’t mention in the text. I would also suggest to not show correlation values if not significant. It would be interesting however to compare nutrient concentration to the metrics mentioned above, or to also relate them to fluxes below. This figure also needs to be described more in depth or removed. Right now this looks like a lot of information and it is hard to extract a clear message from it. For example, is it useful to have the correlation of POC fluxes with depth or salinity?
L551-553. Is there literature data for the area about grazing rates?
L530-532. Could it also be due to lateral transport along the ridge?
L532-533. Here the transfer efficiency would be useful to support this statement.
L542-546. Can you relate that to phytoplankton community structure? What type of particles do we expect? Here a bit of literature regarding the role of the dominant phytoplankton groups in promoting export would be useful.