This study presents a very detailed analysis of the organic aerosol fraction in the marine atmosphere. The author made efforts to try to find a better way of parameterizing the primary and secondary OC in marine aerosols using common measurements of seawater (chl-a and Na+). However, it is not clear about the main conclusion of applying the proposed new method and its performance. Key gaps in interpreting the fluorescent components are missing. I expect further elaborations on these issues together with other major comments. Please see the following comments for details.

Major comments:

1. The authors define marine primary organic carbon MPOC as those emitted from marine bubble bursting. How about those emitted by other processes like wave breaking? The definition of MSOC is even unclear. In the Abstract, it is defined as “secondary organic carbon (MSOC) formed via gas-to-particle conversion remains poorly quantified”. Are these gases those only emitted from the ocean?

How about the primary OC and gas precursors transported from the terrestrial environments?

In summary, it is unclear what does “marine” mean here. Does it only refer to marine atmosphere?

1. L115 “Organic matters were the dominant components in the fine particles, which respectively contributed 18%−75% (40% on average) and 13%−74% (48% on average) of the PM2.5 mass in spring and summer.” The authors measured the mass concentrations of organic matters and inorganic ions. In addition to these measured composition in PM2.5, how about the contribution of other composition, e.g., other metal elements, ions, elemental carbon, in the mass of PM2.5?
2. L118-122: how are the sampling and measurement uncertainties of OC in PM2.5 and TSP? What could be the reasons that “organic fractions were dominant in the submicron marine aerosols”? Could these reasons be consistent with the main sources of MPOC of MSOC?
3. L177-179: is the representativeness of Na+ of overall SSA production also useful in coastal marine atmosphere considering the anthropogenic/terrestrial sources of Na+? The conclusion is derived based on PM2.5 samples. Many marine studies collect TSP or PM10 samples. For these samples, can we interpret the Na+ measurements in this way as well?
4. L244-246 “The estimated MSOC matched better with the WSOC in the marine aerosols when using a combination of [Chl-a] and [Na+] as the input parameters and considering the variation of sea spray aerosols (Fig. 3c, 3g)”. I don’t see the evidence why the estimated MSOC matched better with the WSOC when using a combination of [Chl-a] and [Na+] and considering the variation of sea spray aerosols. The “r” value in Fig. 3c and 3g is the same (0.73). Please further explain.
5. L248 and Fig. 3d & 3h: how about WSOC? Can you compare the estimated MSOC with those estimated by the parameters/methods of Gantt and Vignati?
6. L253-254 “These parameterizations perform well to trace the variation trends of MPOC. However, they might lead to an underestimation of the primary MOA over the Northwest Pacific Ocean.” What could be reasons? Is the difference between MPOC and WIOC can (partly) explain the different performance? Can location/terrestrial aerosols play a role in the difference? Please further explain/discuss.
7. For 3.3, overall, I don’t see clear conclusion between the two methods, [chl-a] vs [chl-a] + [Na+]. From the “4 Summary”, it seems that the authors prefer the second method. However, based on the comparison of Fig. 3b vs 3f and 3c vs 3g, it is not clear to me that the second method performs better. The “r” value is quite the same (0.87 vs 0.88 and 0.73 vs 0.73). Even, the first method performs better by comparing the fraction of points falling between the 1:2 and 2:1 lines in 3b and 3f, which are 69% (L225) and 58% (L243), respectively.
8. 4 and the associated discussion of spatial distribution. How does the season difference affect the spatial distribution?
9. L281-284: the link between TOC in the seawater and “abiotic VOC precursors from the photochemical production in the sea surface microlayer” is missing. Please further elaborate.
10. L310 “This was consistent to the higher mass contribution by MPOC than MSOC in the marine aerosol samples,” There are many samples especially in summer (> half) that have quite low MPOC/OC fractions (< 40%) while the C1 fractions (~ 70% by average) are still very high as the other samples with high MPOC/OC fractions (~ 80%). Therefore, I couldn’t buy it with your statement at the current stage. Please further elaborate. And by the way, Fig. S4 doesn’t show any measurements of Chl-a (L316)

Minor comments:

1. L49 “Ocean surface is one of the largest active reservoirs of organic carbon on Earth, resulting from phytoplankton, algal as well as the related senescence and lysis (Hedges, 1992; Quinn and Bates, 2011).” How large is this reservoir compared to other reservoirs?
2. L86: please add the details of the source for the satellite-derived chl-a data.
3. L97: “organic aerosol concentration”. Please be specific. I guess it is “organic aerosol mass concentration”.
4. L116-117: please show their values (at least a selection of the values) to give the audience a direct sense of “comparable”.
5. L138-139: have you tested the difference of the Chl-a concentration between spring and summer? Are they statistically different?
6. In section 3.2, please further explain why we would expect good or poor correlations between chl-a concentration and organic fraction?
7. L185 “Under certain marine environment conditions (e.g., Chl-a, wind speed, SST etc.), the abundance of MPOC should be constant.” Please further explain what these conditions are with respect to Chl-a, wind speed, SST, etc.
8. Equation L2 and L3: I highly suggest explicitly showing the equation parts like [OC], [Chl-a], etc. in the equations, rather than using those dots. This will make it much easier for readers.
9. Fig 3 caption and the texts referring to Fig 3: Please check the reference carefully. For example:
   1. the “panels (b, d)” in L208 should be “panels (b, f)”.
   2. The “panels (c, f)” in L209 should be “panels (c, g)”.
   3. L231, 233: Fig. 3d should be “3e”
   4. L244: 3d should be “3f”
10. L242: why “p=0.45”? Why not other values within 0.35-0.65?
11. S2 caption: please also add the meaning of the colors.

Review Report of the manuscript titled "Biogenically driven marine organic aerosol production over the Northwest Pacific Ocean by Yujue Wang et al., ( MS No.: egusphere-2025-3951 MS type: Research article)

General Comment: This paper is based on the analysis of PM2.5 samples collected over the Northwest Pacific Ocean during two campaigns in the spring season during 19 Feb.−9 April, 2022,  and in the summer during 19 June−30 July, 2022. The chemical composition data have been investigated to the spatial/regional variability but mainly of Marine organic aerosol (MOA) fractions (WSOC and WIOC, primary and secondary), and Chl-a data as a supporting parameter. While the paper presents a quality data set, the discussion of the results is not up to mark. The basis or tracer data is not enough to quantify the contributions of WSOC and WIOC, primary and secondary to MOA.  Another concern is the ignoring/undermining of the impact of terrestrial biogenic outflow on the OC levels and their composition. Though the impact of long-range transport is mentioned, evidence (like back trajectory analysis) is not provided. The data have been further utilised to parameterise the marine sources. But it is not well presented or summarized how seasonality in sea surface parameters and prevailing environmental conditions could impact the seasonal MOA composition. Further, following specific comments provide the issues to be addressed.

Line 57-58: "regions with high emission rates of MOA are largely related to the spatial" Why high emissions rates only? You may revise "regional emission rates of MOA are largely related to the spatial"

Line 60: "Due to the relationship between sea surface phytoplankton and MOA" I feel this phrase is not required.

Line 64: "Observation-based parameterization..." Provide a reference to support this sentence.

Line 77: As shown in Figure 1(a)  the track covers between 02S-34 N, so it would be appropriate to mention the region as "Northwest Pacific Ocean"? covering southern latitudes

Line 80-81: "suspended particles (TSP) samples and PM2.5" can be revised as "suspended particles (TSP) and PM2.5"

Line 114: "observation, and" should be "observation and"

Figure 1(b) . I suggest to mention the year of the campaigns. You may provide a common x-axis title as (Date/Year).

Line 131: "r = 0.67, p < 0.01, Fig. 1)," r= 0.67 may not represent a strong correlation. Also I dont find correlation plots in Figure 1, perhaps referring to Fig 2?

Line 136: But how about the impact/outflow of terrestrial biogenic emissions. ?

Line 138-139: "spring 138 (0.09 ± 0.06 μg L-1) than  in summer (0.07 ± 0.05 μg L-1)." I think the values are not very different. So the explanation for the differences in OC levels is not robust. I feel the transport from regions of Papua New Guinea and Indonesia needs a consideration. Following works may provide more insights.

https://doi.org/10.1038/s41612-022-00311-0

https://doi.org/10.5194/essd-15-5403-2023

Line 141-142 and other places: "mass ratios of 70% ± 27% in spring and 48% ± 35% in" should be "mass ratios of 70 ± 27% in spring and 48 ± 35% in"

Line 145: "WSPC in marine aerosols." should be "WSOC in marine aerosols."

Line 147-148: "and transferred to atmospheric aerosols over the ocean." Rewrite with a better phrase.

Line 152: "marine reactive organic gases (Boreddy et al., 2018; De Jonge et al., 2024; Miyazaki et al., 2010)." Here I would suggest citing studies which provide measurements of reactive trace gases implying the roles in SOA in marine air. Following works may be cited:

Sources and distribution of light NMHCs in the marine boundary layer of the northern Indian Ocean during winter: Implications to aerosol formation. Journal of Geophysical Research: Atmospheres, 129, e2023JD039433. https://doi.org/10.1029/2023JD039433

Elevated levels of biogenic nonmethane hydrocarbons in the marine boundary layer of the Arabian Sea during the intermonsoon. Journal of Geophysical Research: Atmospheres, 125, e2020JD032869. https://doi.org/10.1029/2020JD032869..

Further, in this section, I suggest comparing the composition of WSOC, WISOC, and other species presented in typically continentally influenced air over this region. The following work may be useful in this regard (It would be good if you can find some other similar works and highlight those)

 Anthropogenic aerosols observed in Asian continental outflow at Jeju Island, Korea, in spring 2005, J. Geophys. Res., 114, D03301, doi:10.1029/2008JD010306.

Line 155: "..through the ocean bubble bursting." why through bubble bursting only as other air-sea exchange processes can also contribute?. Please explain and revise accordingly.

Line 158-160: "in th present .." I think similar discussion is presented in previous section (line 143-144). I suggest to concise the discussion related to correlation in one section only.

Line 170: "concentrations of OC or WIOC in PM2.5 did not show obvious correlations with" I disagree here. The levels OC and WIOC tend to decrease rapidly with wind speed (may not be linear). The discussion should be based on dependencies or trend (with Chl-a and wind speed) but not strictly in terms of correlation/ anti-correlation (as data points are scattered)

Line 172: "which was due to the elevated proportions of inorganic sea salts in the marine aerosols under the high-wind" This justification is not convincing. That can change only the magnitude of the slope but not the direction (positive/negative), check.

Line 185: "Under certain marine environment conditions (e.g., Chl-a, wind speed, SST etc.)," What is certain here , as values of these parameters are not given. And why MPOC should be constant anyway?

Line 188: "Based on the shipboard observations in present study," Should be "In the present study,"

Line 191: "contribution of SOA (e.g., methanesulfonic acid from DMS oxidation," Check if DMS oxidation provides SOA, I know it gives sulfate. But then do you consider sulfate as SOA ? Check following and other papers on DMS

Processes controlling DMS variability in marine boundary layer of the Arabian Sea during post-monsoon season of 2021. Journal of Geophysical Research: Atmospheres, 130, e2024JD042547. https://doi.org/10.1029/2024JD042547

Line213-214: "Based on the correlation analysis above," should be "Based on the correlation analysis"

Line 215-219: "In the classic OC/EC ratio method...Yu et al., 2021)."  These sentences appear out of context , may be removed.

Figure 4 (a-d): Y-axis should be Latitude . Also check Fig 4 (e-f) if axes titles are correct (latitude /longitude or vice versa) .

Line 272:"high concentrations over the oceanic regions among 5°S–5°N and 35°N–40°N," Here for these two region, why the contributions from the land vegetation should also be discussed (due to vicinity to land/island regions)

LIne 279-280" "from surface seawater as well as the production of biologic VOCs (e.g., isoprene, DMS, etc.) from phytoplankton" should be revised as "from seawater as well as the production of VOCs from phytoplankton" but again terrestrial contributions should be discussed.

Line 284-286: "The strong.." This sentence seems speculative also Chl-a map does not support this localized feature.

This manuscript presented an investigation on the marine organic aerosol over Northwest Pacific Ocean. It is important to gain better understanding regarding the contribution of primary and secondary organics over the marine environments. This study provided valuable data sets of organic aerosol compositions in this understudied ocean. This manuscript proposed a parameterization approach to estimate this contribution and compared to other methods. This manuscript is overall well written and fits to the scope of this journal. There are a few issues I suggest to be addressed in the revision.

1. The abstract should present or summarize more on the quantitative results of the study.
2. L96-98, please elaborate the use of 1.6 factor to covert OC to organic aerosol concentration.
3. L177-178, do you mean indicator of the overall organic production? If not, this is misleading and please provide evidences or references to support and justify this statement.
4. L187-188, L252, It would be helpful if the parameterizations from Gantt et al (2011) and Vignati et al. (2010) can be shown somewhere in the main text or supplementals, so readers can have a direct comparison.
5. L207, L220, It is not clear why the 0-30 percentiles of ratios are chosen. Do the results change if different percentiles are selected?