Distinct Peaks of UV-Absorbing Compounds in CDOM and Particulate Absorption Spectra of Near-Surface Great Barrier Reef Coastal Waters, Associated with the Presence of Trichodesmium spp. (NE Australia)

Round 1

Reviewer 1 Report

The authors provide a revised version allowing a quality reaching published science standard. The authors reply concerning a_ph as described on page 6, lines 170-171 is inefficient because we does not find it in the revised version. We recommend publishing the paper according to these suggestions:

Figure 1, we suggest using a map or an image positioning the GBR Lagoon, the Keppel Bay and the Barrier Reef.

The definition of “Level 1 top of atmosphere” could be given, line 219-220.

Missing units was a tricky point; by example, 16.8 and 9.2 stay without unit at lines 311-312. We suggest checking such numbers throughout the paper, another example: 0.014 and 0.016 line 484.

Defining a_ph will clarify reading line 470.

Typo: anomolies> anomalies, line 89; Trichodesmium spp. lines 544, 225

Author Response

We would like to thank Reviewer 1 for suggestions which improved the manuscript.

Responses:

R1: Figure 1, we suggest using a map or an image positioning the GBR Lagoon, the Keppel Bay and the Barrier Reef.

We have made the changes suggested to Figure 1.

R1: The definition of “Level 1 top of atmosphere” could be given, line 219-220.

This part of the sentence has been removed to avoid confusion.

R1: Missing units was a tricky point; by example, 16.8 and 9.2 stay without unit at lines 311-312. We suggest checking such numbers throughout the paper, another example: 0.014 and 0.016 line 484.

In both examples sited there are no units. The values on lines 311-312 are enhancement factors and not concentrations and do no have units. The values on line 484 are ratios which again are unitless.

R1: Defining a_ph will clarify reading line 470.

We have rwwritten the definition of aph (lines 179-1820 in the revised manuscript.

R1: Typo: anomolies> anomalies, line 89; Trichodesmium spp. lines 544, 225

The typos mentioned have been corrected.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript is poorly written, with no novelty, and no new findings highlight. The images are not well drawn, especially Figure 2.

Author Response

Figure 2 has been changed to improve clarity.

Reviewer 3 Report

This is an extremely well written paper that is based on a substantial body of work by the authors. The authors analyzed in detail the development and effects of Trichodesmium blooms with a very extensive complete in-situ optical and biological instrumentation. The results are extensively and precisely described and very clearly studied and presented. The field results are compared in detail with coincident satellite remote sensing. The implications of the UV spectrum contribution of Trichodesmium are significant for tailoring the satellite remote sensing algorithms to specific affected regions. The author’s demonstrations of the necessity both to surface sample and extend the spectral range covered by in-situ instrumentation to the 300 nm region to properly assess the CDOM spectral contribution in remote sensing retrieval algorithms are a significant contribution and should be widely shared among the remote sensing community. For these reasons I recommend publication of this paper.

Author Response

The authors thank Reviewer 3 for their kind comments.

Round 2

Reviewer 2 Report

Yes, it has improved a little.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The authors address the UV light absorption in water samples carried out at the water surface and near under the water surface. The water samples contain a community of m-organism Trichodesmium spp. Which can explain the presence of peaks in the absorption coefficient.

The paper is interesting to follow but the paper flow is imperfect rendering difficult for the reader to assemble the research objectives, methods and results. Numerous explanations are given here under (science, edition, typos). Our conclusion is that the paper requires a large revision. We notice that the text is edited without line numbers and more difficult is review feedback.

Science

The paper mentions the importance of bottle filling method, but does not deliver the reason of such carefulness. A figure could explain more the surface and sub-surface sampling methods. The physical parameters could be considered (calm water middle p 13). Several physical parameters may explain the buoyancy differences, salinity, temperature, organism gas.

The number of stations is numerous, but it is not clear why only some ones are used.

The usage of a spectrophotometer at 360 nm could suggest that a spectrofluorometer (SAFAS-Flx) can also target the 360 nm. The paper should present the hypothesis done.

End p1, add label, eq(1), unit of coefficient 2.3, add definition of coefficient 2.3, add similar equations for a_ph (fig 3 caption) and a_p (Table 2).

The relation between the ocean images (fig 2) and the absorption curves (fig 3) should be clarified. The paper could present an analysis performing the relation between the micro-scale and the large-scale. Moreover, it is not clear in the research presentation if that link is performed by the paper.

The paper presents MERIS. The paper could present this hypothesis, with respect to others means, CMEMS (Copernicus), Sentinel 3 and MODIS.

The community density Trichodesmium spp. could play a role. The paper could detailed this aspect (200 Trichodesmium spp. p 12).

Input and output of algorithm could be presented.

Edition

The italic style for “Trichodesmium spp.” should remain constant along the text.

“Short wavelengths in the visible region” is blue (abstract), the related sentence in the abstract could be edited.

The introduction is not clear about the relation between the research done and the satellite imagery giving ocean colour. It is the same with Chl-a. Is-it an objective of the paper?

HPLC should be named, and CDOM declined.

Add units in Table 1, Lat, Lon, Time

“modified method” could be clarified, 3^rd line, p5

The world “shoulder” may be improved for curve fitting.

Clarify the y-axis label  “a” uses for both a_ph and a_CDOM

Check caption of Table 2, CDOM is a matter; add units in Table 2

Edit 2^nd and 3^rd sentences p 10; edit 1^st middle part of page 14

The paragraph could be numbered at p 10

MODIS scale for Chl-a can be 0.1-15 mg/m³, but the scale of fig 4 is unclear and we could look precisely at 0.1 and over 3.

Typos

Check photo-acclimation 2^nd paragraph, p2

“and composition and” could be edited, 3^rd paragraph, p3

The units must be checked or corrected: um (end p3, middle p 12), mm (1^st and 2^nd paragraphs p 5), MCI radiance and colour scale units (p 6)

“site 9 samples” could be edited, last line, p 3

“at 1000” should use time unit (p 6)

Add year 10-11 September, p 6

Table1 p 6 (missing space)

(0.49 p 14

,. p 15

 photprotective p 19

Refs 36 and 39 cannot have the same page numbers; they come from a same proceeding.

Reviewer 2 Report

Review report on “Distinct peaks of UV-absorbing compounds in CDOM and par-ticulate absorption spectra, of near-surface coastal waters, asso-ciated with the presence of Trichodesmium spp. (NE Australia)” by Lesley A. Clementson et al.

1. In the introduction section, the authors should mention the relevant literature on the comparison of MERIS satellite data with field observations, and emphasize why the author's research is important and what specific topics need to be analyzed and discussed.
2. Figure 1: It is very important to add seabed terrain data, especially when discussing CDOM, etopo1 or terrain from other sources can help the author to simply present.
3. The field observation data is the data of 2003, which has been 20 years since. Why does the author have to analyze it until now?
4. "Data availability statement" is very important, and the author must fill it in the manuscript.
5. Section 2.4: "(error! Reference source not found.)", Please correct it.
6. Figure 2: it must be redrawn. The land area is redundant. The data of the estuary should be highlighted. The image is too small to see the data carefully.
7. Obviously, the authors used a lot of space to explain the results of field observations. MERIS satellite data seems to be used only to present spatial distribution. It seems that the authors did not compare the results of MERIS with field observations. This will greatly reduce readers' motivation to read, not to mention a set of time-specific databases long ago. For the author's contribution to the "Remote Sensing" Journal, the main story of the manuscript should be contributed by satellite data, and the whole main structure and story should also be dominated by MERIS. At present, the content of the manuscript is very much like experimental notes without substantive analysis. The most important thing is what kind of readers the authors expect to see the manuscript. From my point of view, I would like the authors to analyze the band data of MERIS and the field observation data for more detailed comparison in different locations. In addition, the author also needs to investigate the hydrological characteristics here, and what are the effects of rivers and tides? More importantly, the author's manuscript was submitted to "coral reefs remote sensing", but the whole study has nothing to do with coral reefs. I didn't even find the word "coral reefs" in the manuscript.

Reviewer 3 Report

No comment in this moments.