the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Aug 2024
Magnesium (Mg/Ca, δ26Mg), boron (B/Ca, δ11B), and calcium ([Ca2+]) geochemistry of Arctica islandica and Crassostrea virginica extrapallial fluid and shell under ocean acidification
Abstract. The geochemistry of biogenic carbonates has long been used as proxies to record changing seawater parameters. However, the effect of ocean acidification on seawater chemistry and organism physiology could impact isotopic signatures and how elements are incorporated into the shell. In this study, we investigated the geochemistry of three reservoirs important for biomineralization – seawater, the extrapallial fluid (EPF), and the shell – in two bivalve species, Crassostrea virginica and Arctica islandica. Additionally, we examined the effects of three ocean acidification conditions (ambient: 500 ppm CO2, moderate: 900 ppm CO2, and high: 2800 ppm CO2) on the geochemistry of the same three reservoirs for C. virginica. We present data on calcification rates, EPF pH, measured elemental ratios (Mg/Ca, B/Ca), and isotopic signatures (δ26Mg, δ11B). In both species, comparisons of seawater and EPF Mg/Ca and B/Ca, [Ca2+], and δ26Mg indicate that the EPF has a distinct composition that differs from seawater. Shell δ11B did not faithfully record seawater pH and δ11B-calculated pH values were consistently higher than pH measurements of the EPF with microelectrodes, indicating that the shell δ11B may reflect a localized environment within the entire EPF reservoir. In C. virginica, EPF Mg/Ca and B/Ca, as well as absolute concentrations of Mg, B, and [Ca2+], were all significantly affected by ocean acidification, indicating that OA affects the physiological pathways regulating or storing these ions, an observation that complicates their use as proxies. Reduction in EPF [Ca2+] may represent an additional mechanism underlying reduction in calcification in C. virginica in response to seawater acidification. The complexity of dynamics of EPF chemistry suggest boron proxies in these two mollusc species are not straightforwardly related to seawater pH, but ocean acidification does lead to both a decrease in microelectrode pH and boron-isotope-based pH, potentially showing applicability of boron isotopes in recording physiological changes. Collectively, our findings show that bivalves have high physiological control over the internal calcifying fluid, which presents a challenge to using boron isotopes for reconstructing seawater pH.
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Status: open (until 23 Sep 2024)
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RC1: 'Comment on egusphere-2024-1957', Anonymous Referee #1, 23 Aug 2024
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This manuscript deals with an interesting topic: bivalve calcification processes in relation to ocean acidification. However, in a present for, it is not suitable for publication.
The introduction section is too long and should be significantly reduced. Parts of it are hard to follow. The Material and Methods are not sufficiently clearly presented, as relevant information is missing. The choice of target species is not clearly presented; it is not clear why the authors chose to analyse slow-growing Arctica islandica rather than some faster-growing species with an aragonitic shell. Shell sizes used, as well as the number of shells used in the research, are not clearly presented.
Overall, the manuscript appears more as a draft version rather than a complete document. There are serious issues with the organisation of text, Figures and Tables. Numerous mistakes in text and references are questioning the systematic approach of authors in data analysis. Statistical analysis used is not fully credible. The number of Figures is too large. The discussion as well as Conclusions sections are too long. There is a certain level of repetition between the Discussion and Introduction sections, which is redundant and needs to be revised. In the Discussion section, authors need to start by clearly identifying their most important findings and explaining them in a clear and focused way in relation to previous research.
Specific comments:
Line 38 – insert “e.g.,” in the beginning of brackets. Use this approach in other parts of the text where you are just presenting selected references for a certain statement.
Line 43 – replace “e.g..” with “e.g.,”
Line 43 & 50 & 137 – not sure what you mean by “reviewed”, why not just citing the reference
Line 60 – place relevant references after mentioning individual species names and not at the end of the sentence.
Line 77 – did you mean Zhao et al. 2018? There is no publication from 2016 in reference list. Needs to be checked in detail.
Line 81 – a reference to the Figure should be before the Figure, move the Figure below this text
Figure 1 – consider increasing a bit font site on the bottom of the right figure part
Line 88 – remove extra dot
Line 89 – check the presentation of isotope names and formatting of numbers
Lines 88-90 Species names should be presented in italic font
Table 1 – the title should be presented above the table. Extra horizontal and vertical lines should be omitted from the Table for clarity. This table should not be presented in the Introduction section – it actually contains the Results of this study. It is not sufficiently clearly explained why parameters marked with n.d. were not measured.
Line 96 – it is not clear why the authors refer here to Table 1 and Zhao et al. 2018 paper – and to which of them – as two are listed in the reference section. Did you want to refer to Figure 1? There you cite Zhao et al. 2016 paper.
Line 109 – At the end there is only a reference to Crenshaw (1972), so check “et al.”
Line 111 – year missing after Crenshaw
Line 143- 145 place references after corresponding taxa, not at the end of the sentence
Lines 150-160 & other parts of the text. There is no need to go in so much detail in relation to other taxa. You text is too wide and too descriptive. You need to focus on target taxa and main questions.
Line 164 Full species name is mentioned before in text, so abbreviations should be used here-
Line 176 Authors need to provide a short description of collection and culturing in this manuscript, it is not sufficient to refer to earlier manuscript. There is no sufficient indication of year research was conducted.
Line 178 & other parts of the text – remove “psu”
Line 182 you need to clearly specify size of bivalves used in your research as well as sample number
Line 183 – check the formatting of geo coordinates
Line 190 what do you ean by “see” here?
Line 191 – here you refer to Table a that is presented several pages before – this is not appropriate approach to organisation of the manuscript
Line 194 you need to define “dry weight”. What did you measure & with what? What was the precission?
Line 195 You need to define “buoyant weight”
Line 207 Arctica islandica is a slow growing species – you need to explain why you choose 14 days as period here.
Line 212 You need to present Figure/diagram clearly illustrating how sampling of shell carbonate material was conducted.
Line 232 A sentence should not start with a number, revise
Line 289 You refer here to Table 3 – and it is presented much later in the manuscript. There are serious issues with the organisation of your text, Figures and Tables.
Line 294 & other parts of text - Species names should be presented in italic font.
Line 304 – check the formatting of Fig – “a” vs. “A”
Line 320 – statistical analysis used should be clearly presented in Material and Methods section. Did you test your data for homogeneity of variance (requirement of t test)? See for example Fig 3f – variances are not clearly not homogeneous according to your data presentation.
Careful formatting of references is needed. Journal names are not consistently presented, as some are referred to by full names and others by their abbreviations. I did not check all in detail, and the following are just some observations: Lines 644-647 – check for use of capital letters in publication titles. Line 646 replace “mollusc” with “Mollusc”. Line 652 – place “Porites” in italics, also check other references and present all species scientific names in italics font. Line 670 – year should be placed at the end of the reference for consistency. Line 677 – doi missing. Line 681 – capital letters are used, needs to be corrected.
Citation: https://doi.org/10.5194/egusphere-2024-1957-RC1
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