the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 01 Oct 2025
Technical note: Development of an extraction protocol and colorimetric analysis for alginate in marine sediment
Abstract. Transportation of organic carbon from coastal macroalgae, particularly brown algae, to deeper ocean layers has recently attracted attention as an effective mechanism for carbon sequestration. However, no observational data are currently available on the amounts of organic carbon derived from brown algae in marine environments such as seawater or sediments. In this study, we developed an extraction protocol for alginate, a polysaccharide unique to brown algae that accounts for 20–30 % of their dry weight, to provide quantitative and direct evidence of brown algal carbon sequestered in ocean sediments. Alginate extraction and colorimetric analysis methods are well established in food chemistry: we modified these techniques to apply them to marine sediments, which are characterized by high concentrations of cations (e.g., Ca, Mg, Fe) and humic substance-like high-molecular-weight organic compounds. We applied this new method to sediment samples collected from coastal waters around Hokkaido, Japan. Alginate contents were quantified as 6.11–26.0 mg m−2 in Funka Bay, 39.0–41.3 mg m−2 in Hakodate Bay, 11.8–14.7 mg m−2 off Cape Esan, and 58.3–74.1 mg m−2 off Muroran.
- Preprint
(1131 KB) - Metadata XML
-
Supplement
(594 KB) - BibTeX
- EndNote
Status: open (until 11 Feb 2026)
-
RC1: 'Comment on egusphere-2025-4577', Anonymous Referee #1, 01 Dec 2025
reply
-
AC1: 'Reply on RC1', Sota Nakazato, 22 Dec 2025
reply
We sincerely appreciate the time you devoted to reviewing our manuscript and for providing constructive and insightful comments. We are also grateful for your positive evaluation of the protocol from both scientific and practical perspectives. Based on your valuable suggestions, we have prepared detailed responses to each of your comments below. We hope that our explanations adequately address your concerns, and we thank you again for your thoughtful feedback.
1: Unify the format of units, w/w or w·w−1
To address this comment, we have unified the formatting of concentration units throughout the manuscript. Specifically, all solution concentrations previously expressed as “% (w/v or v/v)” have been revised to “g L−1” or “mL L−1,” as appropriate. We have also replaced the descriptive ratio-style expression for alginate in sediments, “mg per 300 g (alginate/wet weight of sediment),” with the standardized notation “mg 300 g−1”.
2: Why yield is expressed per 300 g ?
We originally expressed alginate yield as “mg per 300 g” to indicate the amount of alginate extracted from each sediment sample, whose wet weight was fixed at 300 g. In response to your comment, we have standardized this notation to “mg 300 g−1” throughout the manuscript.
The rationale for selecting 300 g as the sediment sample weight has also been clarified in Section 2.3, where we added the statement: “The weight of 300 g corresponds approximately to the amount of sediment collected from the upper 0–1 cm layer using a grab sampler.”
To further improve clarity, we have added a note indicating “Sediment sample weight = 300 g (wet)” in Tables 2, 5, and 8, where alginate yield (mg 300 g−1) is reported. These revisions improve consistency and readability in the presentation of the alginate yield data.
3: Latin names in References should be in italics
Thank you for pointing this out. All Latin names appearing in the references have been converted to italic font in accordance with the journal’s formatting requirements.
Please note that these changes will be incorporated into the revised manuscript.
Citation: https://doi.org/10.5194/egusphere-2025-4577-AC1
-
AC1: 'Reply on RC1', Sota Nakazato, 22 Dec 2025
reply
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 267 | 116 | 25 | 408 | 36 | 26 | 25 |
- HTML: 267
- PDF: 116
- XML: 25
- Total: 408
- Supplement: 36
- BibTeX: 26
- EndNote: 25
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
The manuscripts presents a study on the development of a method adapted to the determination of alginate in sediments.
The interest of this modified protocol is well justified, both from a scientific and from practical approaches. The work planning is well presented and the results are clearly presented and discussed.The authors used the protocol to characterize samples from different locations.
Only minor comments are suggested:
Unify the format of units, w/w or w·w-1
Why yield is expressed per 300 g?
Latin names in References should be in italics