A global database of dissolved organic matter (DOM) measurements in coastal waters (CoastDOM v1)

Lønborg, Christian; Carreira, Cátia; Abril, Gwenaël; Agustí, Susana; Amaral, Valentina; Andersson, Agneta; Arístegui, Javier; Bhadury, Punyasloke; Bernardi Bif, Mariana; Borges, Alberto V.; Bouillon, Steven; Ll. Calleja, Maria; Cotovicz Jr., Luiz C.; Cozzi, Stefano; Doval, Maryló; Duarte, Carlos M.; Eyre, Bradley; Fichot, Cédric G.; García-Martín, E. Elena; Garzon-Garcia, Alexandra; Giani, Michele; Gonçalves-Araujo, Rafael; Gruber, Renee; A. Hansell, Dennis; Hashihama, Fuminori; He, Ding; Holding, Johnna M.; Hunter, William R.; Ibánhez, J. Severino P.; Ibello, Valeria; Jiang, Shan; Kim, Guebuem; Klun, Katja; Kowalczuk, Piotr; Kubo, Atsushi; Weng Lee, Choon; Lopes, Cláudia B.; Maggioni, Federica; Magni, Paolo; Marrase, Celia; Martin, Patrick; McCallister, S. Leigh; McCallum, Roisin; Medeiros, Patricia M.; Morán, Xosé Anxelu G.; Muller-Karger, Frank; Myers-Pigg, Allison; Norli, Marit; Oakes, Joanne M.; Osterholz, Helena; Park, Hyekyung; Lund Paulsen, Maria; Rosentreter, Judith A.; Rueda-Roa, Digna; Santinelli, Chiara; Shen, Yuan; Teira, Eva; Tinta, Tinkara; Uher, Guenther; Wakita, Masahide; Ward, Nicholas; Watanabe, Kenta; Xin, Yu; Yamashita, Youhei; Yang, Liyang; Yeo, Jacob; Yuan, Huamao; Zheng, Qiang; Álvarez-Salgado, Xosé Antón

doi:https://doi.org/10.5194/essd-2023-348

Preprints

https://doi.org/10.5194/essd-2023-348

Preprints

27 Sep 2023

| 27 Sep 2023

Status: this preprint is currently under review for the journal ESSD.

A global database of dissolved organic matter (DOM) measurements in coastal waters (CoastDOM v1)

Christian Lønborg, Cátia Carreira, Gwenaël Abril, Susana Agustí, Valentina Amaral, Agneta Andersson, Javier Arístegui, Punyasloke Bhadury, Mariana Bernardi Bif, Alberto V. Borges, Steven Bouillon, Maria Ll. Calleja, Luiz C. Cotovicz Jr., Stefano Cozzi, Maryló Doval, Carlos M. Duarte, Bradley Eyre, Cédric G. Fichot, E. Elena García-Martín, Alexandra Garzon-Garcia, Michele Giani, Rafael Gonçalves-Araujo, Renee Gruber, Dennis A. Hansell, Fuminori Hashihama, Ding He, Johnna M. Holding, William R. Hunter, J. Severino P. Ibánhez, Valeria Ibello, Shan Jiang, Guebuem Kim, Katja Klun, Piotr Kowalczuk, Atsushi Kubo, Choon Weng Lee, Cláudia B. Lopes, Federica Maggioni, Paolo Magni, Celia Marrase, Patrick Martin, S. Leigh McCallister, Roisin McCallum, Patricia M. Medeiros, Xosé Anxelu G. Morán, Frank Muller-Karger, Allison Myers-Pigg, Marit Norli, Joanne M. Oakes, Helena Osterholz, Hyekyung Park, Maria Lund Paulsen, Judith A. Rosentreter, Digna Rueda-Roa, Chiara Santinelli, Yuan Shen, Eva Teira, Tinkara Tinta, Guenther Uher, Masahide Wakita, Nicholas Ward, Kenta Watanabe, Yu Xin, Youhei Yamashita, Liyang Yang, Jacob Yeo, Huamao Yuan, Qiang Zheng, and Xosé Antón Álvarez-Salgado

Abstract. The measurements of dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) are used to characterize the dissolved organic matter (DOM) pool and are important components of biogeochemical cycling in the coastal ocean. Here, we present the first edition of a global database (CoastDOM v1; available at https://figshare.com/s/512289eb43c4f8e8eaef) compiling previously published and unpublished measurements of DOC, DON, and DOP collected in coastal waters. These data are complemented by hydrographic data such as temperature and salinity and, to the extent possible, other biogeochemical variables (e.g., Chlorophyll-a, inorganic nutrients) and the inorganic carbon system (e.g., dissolved inorganic carbon and total alkalinity). Overall, CoastDOM v1 includes observations from all continents however, most data were collected in the Northern Hemisphere, with a clear gap in coastal water DOM measurements from the Southern Hemisphere. The data included were collected from 1978 to 2022 and consist of 62339 data points for DOC, 20360 for DON and 13440 for DOP. The number of measurements decreases progressively in the sequence DOC > DON > DOP, reflecting both differences in the maturity of the analytical methods and the greater focus on carbon cycling by the aquatic science community. The global database shows that the average DOC concentration in coastal waters (average (standard deviation; SD): 182 (314) µmol C L⁻¹; median: 103 µmol C L⁻¹), is 13-fold greater than the average coastal DON concentrations (average (SD): 13.6 (30.4) µmol N L⁻¹; median: 8.0 µmol N L⁻¹), which was itself 39-fold greater than the average coastal DOP concentrations (average (SD): 0.34 ± 1.11 µmol P L⁻¹; median: 0.18 µmol P L⁻¹). This dataset will be useful to identify global spatial and temporal patterns in DOM and to facilitate reuse of DOC, DON and DOP data in studies aimed at better characterising local biogeochemical processes, closing nutrient budgets, estimating carbon, nitrogen and phosphorous pools, as well as identifying a baseline for modelling future changes in coastal waters.

How to cite. Lønborg, C., Carreira, C., Abril, G., Agustí, S., Amaral, V., Andersson, A., Arístegui, J., Bhadury, P., Bernardi Bif, M., Borges, A. V., Bouillon, S., Ll. Calleja, M., Cotovicz Jr., L. C., Cozzi, S., Doval, M., Duarte, C. M., Eyre, B., Fichot, C. G., García-Martín, E. E., Garzon-Garcia, A., Giani, M., Gonçalves-Araujo, R., Gruber, R., A. Hansell, D., Hashihama, F., He, D., Holding, J. M., Hunter, W. R., Ibánhez, J. S. P., Ibello, V., Jiang, S., Kim, G., Klun, K., Kowalczuk, P., Kubo, A., Weng Lee, C., Lopes, C. B., Maggioni, F., Magni, P., Marrase, C., Martin, P., McCallister, S. L., McCallum, R., Medeiros, P. M., Morán, X. A. G., Muller-Karger, F., Myers-Pigg, A., Norli, M., Oakes, J. M., Osterholz, H., Park, H., Lund Paulsen, M., Rosentreter, J. A., Rueda-Roa, D., Santinelli, C., Shen, Y., Teira, E., Tinta, T., Uher, G., Wakita, M., Ward, N., Watanabe, K., Xin, Y., Yamashita, Y., Yang, L., Yeo, J., Yuan, H., Zheng, Q., and Álvarez-Salgado, X. A.: A global database of dissolved organic matter (DOM) measurements in coastal waters (CoastDOM v1), Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2023-348, in review, 2023.

Received: 01 Sep 2023 – Discussion started: 27 Sep 2023

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Christian Lønborg et al.

Status: final response (author comments only)

RC1: 'Comment on essd-2023-348', Anonymous Referee #1, 08 Nov 2023

The authors took tremendous efforts to collect published and unpublished DOC, DON and DOP concentration measurements from global coastal regions and provided a useful dataset to the marine biogeochemistry and DOM community. The dataset is well-organized, and the manuscript introduced this open-access dataset well. It may require some revisions that could help improve the paper.

Suggestions:
Title: I suggest specifying what “dissolved organic matter (DOM) measurements” refer to in the title to make it clearer. I believe they are “Dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) concentration measurements”.

Lines 262-268: Hansell et al,. 2021 DOM data compilation only contains the TDN and DOC concentration measurements. It may be helpful if adding some discussions here about existing open ocean DOP concentration dataset such as an old DOP concentration database called “GOOD DOP” in a book chapter (Karl & Björkman, 2015) and a recently compiled open-access open ocean DOP concentration database (DOPv2021) (Liang et al., 2022).

Reference:
Karl, D. M. & Björkman, K. M. Chapter 5 - Dynamics of dissolved organic phosphorus. in Biogeochemistry of Marine Dissolved Organic Matter 2nd edn (eds. Hansell, D. A. & Carlson, C. A.) 233–334, https://doi.org/10.1016/B978-0-12-405940-5.00005-4 (Academic Press, 2015).

Liang, Z., McCabe, K., Fawcett, S.E. et al. A global ocean dissolved organic phosphorus concentration database (DOPv2021). Sci Data 9, 772 (2022). https://doi.org/10.1038/s41597-022-01873-7

Lines 290-293: Some articles might use key words such as “Total organic carbon”, “Total dissolved nitrogen”, “Total dissolved phosphorus”, “Total organic nitrogen”, and “Total organic phosphorus”. I am not sure if only using the terms “dissolved organic carbon”, “dissolved organic nitrogen”, and “dissolved organic phosphorus” would miss some published data.

Lines 308-310: After oxidation of DON samples, the resulting total nitrate can also be measured by the nitric oxide chemiluminescence method (Knapp et al., 2005;) not just colorimetric method.

Reference:
Knapp, A. N., Sigman, D. M., & Lipschultz, F. (2005). N isotopic composition of dissolved organic nitrogen and nitrate at the Bermuda Atlantic Time‐series Study site. Global Biogeochemical Cycles, 19(1).

Lines 301-308: I believe it needs references here for the approaches for TOC and TDN concentration measurements. Below are some resources.

For TOC: Sharp, J. H., Benner, R., Bennett, L., Carlson, C. A., Dow, R., & Fitzwater, S. E. (1993). Re‐evaluation of high temperature combustion and chemical oxidation measurements of dissolved organic carbon in seawater. Limnology and Oceanography, 38(8), 1774-1782.

For TDN: in the Chapter 4 of the book “Biogeochemistry of marine dissolved
organic matter”, it summarizes different oxidation approaches for DON and includes their references.

Lines 314-317: For TDP analysis, besides UV and wet chemical oxidation, there is another oxidation approach “ash/hydrolysis”. Details of the “ash/hydrolysis” approach can be found in Solórzano & Sharp 1980. However, perhaps no DOP data in this database employed the "ash/hydrolysis" approach?

Reference:
Solórzano, Lucia, and Jonathan H. Sharp. "Determination of total dissolved phosphorus and particulate phosphorus in natural waters." Limnology and Oceanography 25.4 (1980): 754-758.

Line 407: what is the detection limit here for DOC. DON and DOP concentration measurements?

Lines 496-509: How many data points have all DOC, DON and DOP concentration measurements? The article says that observations of DON and DOP concentrations are much less than DOC concentrations. I would add a recommendation here to acknowledge this feature and encourage more paired measurements of DOC, DON and DOP concentrations.

Figures: Why not add a figure to show number of observations for dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) concentrations in different months? I would also distinguish samples from the northern hemisphere and southern hemisphere. This figure will help readers check the potential bias due to sampling seasons.

Minor comments:
Lines 205-206: I would add the word “concentrations” to clarify these measurements are DOC, DON and DOP concentrations. Similar for other texts in the article. For example, use “DON concentration observations” instead of “DON observations”.

Line 241: I would use “organic material” here.

Lines 246-248: I find this sentence a bit difficult to follow. Why POM less degraded but more bioavailable?

Figure 1c: x- axis unit should be µmol P L^-1

Citation: https://doi.org/10.5194/essd-2023-348-RC1
RC2: 'Comment on essd-2023-348', Anonymous Referee #2, 14 Nov 2023

DOM represents a huge reservoir for biogenic elements and should be playing an important role in marine biogeochemical cycles. Given that most coastal waters are among the most dynamic and productive areas in the global ocean, a better understanding of DOM cycle in such environment is essential.However, there is clearly a huge gap between DOM data availability and its biogeochemical importance in coastal waters globally. To address the concern the authors here firstly present the most comprehensive database of DOM concentration in the global coastal waters to date, covering a wide range spatially and temporally as well. The aims of this work are clear and will be of interest to the wide readership of ESSD. It will also likely be a highly cited work considering the urgent call for such a comprehensive compilation of published+unpublished DOM concentration data. In general, the authors did a good job on data compilation. The manuscript is well written and well organized and will be a contribution to the aquatic science community.
Major comments
Title. The measurement of DOM can be multifaceted, i.e., concentration, chemical composition, bioavailability, age, isotopic ratios, etc. It’s all about the most important parameter, i.e., concentration, in this effort of compilation.
L279-281. I full agree with the authors that ‘long-term consistency of the measurements, to enable data intercomparison, and establish a robust baseline for assessing,’ is a fundamental issue. The authors have addressed the issue of comparability for data covering a wide range from multiple sources. The authors can provide more information (or give examples in SI) on this in the ms given its importance.
QC assessment part also deserves to be addressed in more detail. I would recommend a flow chart (step/criteria/priority) of data processing and quality control to be presented.
Are there any reliable time-series DOM concentration data included in this compilation that possibly provides a case to present or evaluate temporal variability/human perturbations, which is not generally lacking in its present form?
I would recommend to try an addition of stoichiometry (ratios C/N/P) part. It may unveil the tight link for the elements and provide implications for understanding biogeochemical cycle in the highly dynamic and rapidly changing coastal waters.
Minor comments
L407-408: ‘In cases where concentrations were below the detection limit, the zero values were replaced with half the value of the limit-of-detection.’ I am not sure if this is the best practice. What about leaving it blank?
Typo: The unit on x axis should read ‘umol P L-1) in Fig.1c.
The color is too light for DON line in Fig.2a.
Fig 3 is not clear enough, especially for histograms.

Citation: https://doi.org/10.5194/essd-2023-348-RC2

Christian Lønborg et al.

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A global database of dissolved organic matter (DOM) measurements in coastal waters Christian Lønborg https://figshare.com/s/512289eb43c4f8e8eaef

Christian Lønborg et al.

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Short summary

In this paper, we present the first edition of a global database compiling previously published and unpublished measurements of Dissolved Organic Matter (DOM) collected in coastal waters (CoastDOM v.1). Overall, the CoastDOM v.1 dataset will be useful to identify global spatial and temporal patterns and to facilitate reuse in studies aimed at e.g., better characterising local biogeochemical processes and in identifying a baseline for modelling future changes in coastal waters.


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