In-Situ Variability of DOM in Relation with Biogeochemical and Physical Parameters in December 2017 in Laucala Bay (Fiji Islands) after a Strong Rain Event

Round 1

Reviewer 1 Report

General comments:

The PSU unit is no longer in use.

The authors should use “protein-like component” instead of “proteinic-like component”.

The incorrect use of optical symbols notation according to convention proposed by Morel and Smyth (1982) severely hampers the perception of this manuscript. Authors use notation a_254, a_350, a_412, a₄₄₂ as symbols of CDOM absorption. The symbol convention that has been applied in the field of ocean optics is that wavelength marked in symbolic way with small Greek letter “lambda” is written in the parenthesis after the symbol that mark the optical parameter. Neither  “l” is not written as the subscript nor the numerical notation of wavelength. According to the same convention the absorption is marked with the letter “a”, (in italics) and the wavelength is at which this quantity is measured or referred is given in parenthesis immediately after the absorption symbol. The absorption due to specific optically significant water constituent such as pure water, CDOM, phytoplankton pigments, non-algal particles should be marked in the subscript after the absorption symbol but before the wavelength given in parenthesis. Therefore the symbol for absorption coefficient due to CDOM at wavelength 254 (or any other wavelength) should be properly noted as a_CDOM(254). Authors shall use a proper symbols in the whole text of revised manuscript, figure axis description, figures legend and captions and tables.

More detailed comments follow:

Page 1 Section 1 Introduction:

Line 35: DOM abbreviation should be explained here.

Lines 48-50: Abbreviations DOC, DON, POC, POM should be explained

Line 61: should be “ranging from ultraviolet to blue…”.

Pages 3 and 4: Section:2.2 In-situ sampling and sea measurements: There is a lack of reference to (my guess) Table 1. The information provided in it could be really helpful for a readier at that moment.

The information about parameters measured and for what parameters the water was taken should be also included in here and then could be described in more details later on.

Lines:146-149: It is unclear on what basis the Lacuala Bay was divided into 3 zones. Was the distance from the coast the only condition or are there any earlier research showing that e.g. water parameters are different 1 and 2 km from the shore?

Pages 4-5: Section 2.4 Biogeochemical parameters sample conditioning: Lines 164-165:The information about the sizes of containers and bottles is not crucial at this point unless the authors provide the information about what amount of water was sampled for what parameter. There is only information about cytometry and nutrients.

Lines 173-177: there is a lack of reference to the methodology of SPM.

Lines 176-177: 20 minutes in an oven in 60 °C is a quite short time. How can the author be sure that the filter with it content was already dry? Most researches dry filters for SPM for much longer time. Were the “clean” filters before the first weighting combusted? Did the authors took any “blank” filters?

Lines 179-184: It is unclear for what parameter the authors filtered 25 ml of sea water.

Lines 185-186: The sentence needs to be rewritten.

Page 6: Section 2.5.5 Chla and pheophytin: It would be good if the authors could provide more detailed information about chlorophyll a and pheophytin concentration measurements methodology. The reference provided by the authors - “[57]” – Brando, V., Dekker, A., Marks, A., Qin, Y and Oubelkheir, K., 2006. Chlorophyll and suspended sediment assessment in a macrotidal tropical estuary adjacent to the Great Barrier Reef: spatial and temporal assessment using remote sensing. Cooperative Research Centre for Coastal Zone, Estuary & Waterway Management Technical Report(74), Pp 70-92, has over 100 pages but I could not find such description. What I found was: „Discrete water samples were taken in surface and bottom water at each site for later laboratory analysis of the discrete optical and biogeochemical parameters described in Section 2.2. Oubelkheir et al. (2006) and Radke et al. (2006) summarise the purpose of these measurements and give a brief description of the methods used.”  The Technical report no 74 was used (uncorrectly) as a reference also for other parameters

Page 6: Section 2.5.6 FDOM

Line 232: Please use notation EEM not FEEM

Lines 233-238: The information about how the spectrofluorometer works is not crucial and can be omitted.

Lines 247-249: Does it mean that the authors used an average of two Raman measurements? If so it should be stated more clearly.

Page 7: Section 2.5.6 FDOM

Lines 251-254: What was the total no of EEM used to perform PARAFAC?

Lines 255-258: There is a lack of reference. The authors should provide in text the information of spectral characteristics of derived components e.g. C1 (Ex=?/Em=?). If the authors decided to use “peak” nomenclature e.g. “peak M” they should do the same with the rest of PARAFAC components. What do the authors mean by writing: “…type M peak which may be linked to pollution…”? What kind of pollution? Please, provide reference.

Page 7: Section 3 Results: should be named “Results and discussion”.

Page 8: Section 3.1 Physical conditions in Laucala Bay in December 2017:

Line 299: Did you mean horizontal or vertical distribution or both?

Page 9: Section 3.2 Biogeochemical and nutrients variables

Line 322: Contrastingly to what? The authors write that e.g. DOC “showcased negative gradient in the offshore direction” and in the lines 323-324 the authors write  “…DOC with higher concentrations at the CO and IB..”.

Lines 334-335: Are those values the mean values of all parameters mentioned in this paragraph? Why do the authors write the mean values while describing the gradients of those parameters? Mean values served in this way are difficult to read. It would be more sufficient if this information would be included in Table 3 next to the range of values measured for all stations.

Lines 309-344: What can be the reason of this kind of distribution of mentioned parameters? It is worth to try to answer that question in this section.

Pages 10-11: Section 3.2.1 CDOM absorption and fluorescence:

Can the authors discuss provided results? What proves this kind of distributions?

Lines 346-349: The information included in this paragraph is trivial and should not be mentioned in the article.

Line 353: Should be: …a412 and a442…

Line 359: Components derived with use of PARAFAC are mixtures of fluorophores therefor they should be named “components” not “fluorophores”. Which “all three” components the authors meant?

Lines 373-377: Information about mean values of absorption coefficients should be included earlier together with description of ranges of values of those coefficients. The authors should use “values” not “concentration” of a412. What it is M-1?

Pages 11-13: Section 3.3 Association and dependence of environmental variables:

This section is loaded with information and very hard to read. Maybe it would be easier and shorter to write which parameters do not correlate with each other or present them in the table? It would be good if the authors could conclude this section.

Page 13: Line 445: “…moderate..” what?

Page 18: Section 5 Conclusions:

Line 616-617: Please use components instead of fluorescent intensities.

Page 18: Author contribution:

Lines 647-648: Which means S.N.?

Figures:

Most figures have too small resolution.

Figure 1: The map has a lot of detail which is really hard to read. Please use bigger font. CTD water depth overlay is not crucial. Removing it may improve the map.

Figures 1, 3-6: Please use different color to mark the coral reef (e.g. black). The color chosen by the authors is also used in the color scale what can be misleading.

Figures 3-7: The axes labels are too small. The color scale values font is too small. Rescaling the maps to the sampled area may improve the maps.

Figure 2: Please swap the axes.

Figure 8: The font used in this figure is too small. Why the outliers of each box do not line up?

Figure 9a: The resolution and the size of the graph is too small. In this shape the figures does not bring any information. Maybe it should be show in a supplement.

Figure 9b: What does it mean:HT-1hr?

Figure 10a: There is a lot of information in a very small graph. Maybe the bigger version with better resolution should be presented in a supplement?

Figure 10b: The font should be a bit bigger.

Tables:

Table 1: The caption of table 1 needs to be added. The reference to table 1 needs to be added in the text. Please use T1-T4 in Transect column as in the text.

Table 2: There are two Table2. Please remove the wrong one. Please add the number of observations for each parameter

Table 3. Please add mean values of all stations for all parameters. Please add the number of observations for each parameter. Please explain SL?

Comments for author File: Comments.pdf

Author Response

" Please Refer To Attachment"

Author Response File: Author Response.pdf

Reviewer 2 Report

In-Situ Variability of DOM in relation with biogeochemical and physical parameters in December 2017 in Laucala Bay (Fiji Islands) after a strong rain event

Koliyavu T et al.

General comments

This study examined the effects of heavy rain events on the coastal waters of Laucala Bay, Fiji Islands, small Pacific Islands by the measurements of fluorescence spectroscopy along with PARAFAC model along with nutrients. This study identified the fluorescent components and then identified their linkages with DOM sources. This study also characterized the DOM sources and their linkages with nutrients. There is some gap remained that is needed to address properly. Firstly, fluorescent component, namely type M, should be clearly denoted with proving a specific name (see specific comment) and also rewrite the manuscript accordingly. Second, there are many mistakes on wording that should be addressed properly. Third, what is the key findings from this study that is needed to address at the end of the abstract. There are some grammatical mistakes that is needed to check carefully the whole manuscript.

Specific comments

Line 16: The fluorescent component, namely type M, should be properly denoted and characterized based on published data. This type component is derived from microbial/photorespiration from phytoplankton. Author can read the name of this component in the following reference.

Reference

Fluorescent dissolved organic matter in natural waters. Photobiogeochemistry of Organic Matter: Principles and Practices in Water Environments, Springer, Berlin Heidelberg, Chapter 6, pp 429-559

Line 25: ‘DONs’ should be properly used

Line 45: “DOMs”: It should be used as DOM and revised throughout the manuscript in such wording.

Line 48-50: should be deleted.

Line 70: “microorganisms” is one word.

Line 73-75: deleted

Line 153: superscripts are needed to use properly to address the unit along with providing gap between numbers and unit. There is many issue that is needed such gap throughout the manuscript.

Line 170: HCL should be properly written

Line 229: 2.5.6 FDOM: Author should rewrite this whole section properly and concisely. FEEMs is wrong wording that should be addressed properly throughout the manuscript.  

Author can read the reference mentioned before and also the following reference to address it properly.

Reference:

New insights into mechanisms of sunlight- and dark-mediated high-temperature can accelerate diurnal production-degradation transformation of lake fluorescent DOM. Science of the Total Environment 760: 143377

Line 359: ‘fluorophores’ should be replaced as ‘fluorescent components’ throughout the manuscript

Line 513-515: This is not derived from pollution source. Terrestrial flow can enhance the algal blooms that is the reason, this component is derived from high algal blooms after rain events. You should address this way.

Line 527: “proteinic like fluorophore” can rewrite as protein-like substances

Line 577: “Fluorescent intensities…” should be “Fluorescence intensities…” and also addressed throughout the manuscript

Author Response

"Please see attachment"

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Manuscript is largely improved.

The typical word error is needed to revise.

Lines 19-20: fluorescence component should be ‘fluorescent component’ and also check throughout the manuscript