Influence of oceanic conditions in the energy transfer efficiency estimation of a micronekton model

Delpech, Audrey; Conchon, Anna; Titaud, Olivier; Lehodey, Patrick

doi:https://doi.org/10.5194/bg-17-833-2020

Articles | Volume 17, issue 4

https://doi.org/10.5194/bg-17-833-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/bg-17-833-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 17, issue 4

Research article

|

18 Feb 2020

Research article |

| 18 Feb 2020

Influence of oceanic conditions in the energy transfer efficiency estimation of a micronekton model

Audrey Delpech, Anna Conchon, Olivier Titaud, and Patrick Lehodey

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Final revised paper (published on 18 Feb 2020)
Preprint (discussion started on 06 Sep 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'review of the manuscript: "Influence of oceanic conditions in the energy transfer efficiency estimation of a micronekton model" by Audrey Delpech et al.', Anonymous Referee #1, 09 Oct 2019
- AC1: 'Response to reviewer 1', Audrey Delpech, 28 Nov 2019
RC2: 'review of 'Influence of oceanic conditions in the energy transfer efficiency estimation of a micronekton model'', Anonymous Referee #2, 08 Nov 2019
- AC2: 'Response to reviewer 2', Audrey Delpech, 28 Nov 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (02 Dec 2019) by Ciavatta Stefano

AR by Audrey Delpech on behalf of the Authors (03 Dec 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (04 Dec 2019) by Ciavatta Stefano

RR by Anonymous Referee #1 (07 Dec 2019)

RR by Anonymous Referee #2 (20 Dec 2019)

Suggestions for revision or reasons for rejection

# general comments

I am glad to see that the manuscript has become much easier to follow. There are only a few places where I got stuck and needed to re-read sentences multiple times to try to understand their meaning. One example is Section 4.1 which contains a lot of information (which is a good thing). Unfortunately, sentences in Section 4.1 are often still formulated in a complex or clumsy way -- and the combination of high information density and complex sentences makes it difficult to follow the text, especially for readers who do not know the model very well. I have made some suggestions below but would encourage the authors to go carefully through Section 4.1 again and revise complex sentences.

Quite a lot of emphasis is placed on DVM in the introduction and conclusions of the manuscript, for example: "Among them, the energy transfer efficiency coefficients are of great importance because they directly control the biomass of micronekton functional groups, including those that undergo DVM and contribute to the sequestration of carbon dioxide into the deep ocean ...". I agree with that statement and therefore I don't quite understand why all E_i are usually lumped together in the results section and rarely investigated separately. Are the energy transfer coefficients for micronekton undergoing DVM as well constrained by the data as others? Are there systematic differences?

A minor but general comment: the manuscript currently contains a mix of passive and active voice. This is not a big deal but it seems a bit inconsistent. Example: l 55ff "A method to estimate the model parameters has been developed ... While we can expect that improved estimates ...".

# specific comments

l 1: I would suggest to change this from singular to plural: "Micronekton [...] are"

l 9: "Sampling regions show a variety of performances.": This is not a great sentence, I would suggest to change it to something like: "In our experiments, we obtained different results for spatially distinct sampling regions based on their prevailing ocean conditions."

l 28: I would suggest to add units to the "1" as well.

l 36: "Progresses are" -> "Improvements in biomass estimation"

l 40: "techniques of observational estimates" -> "techniques for collecting observational estimates"

l 50: There is a leftover of the "[["-notation.

l 52: It would be good to describe the relationship between the 4 parameters and the 2 times of development (e.g. "(2 to parameterize recruitment, 2 for mortality)"). And I am not a biologist but I presume "stages of development" is a more suitable term than "times of development".

l 59: "run" -> "model run" or "model simulation"

l 59: How can the same model run be used to generate observations and also estimate parameters? This is not a good description of twin experiments.

l 65: "regarding oceanic variables" -> "characterized by different oceanic regimes"

l 66: "observation gives" -> "observations provide"

l 68: "in order to simulate more realistic conditions": Add "for parameter estimation", otherwise it sounds like the error is making the ocean conditions more realistic.

l 70: "oceanic variables" -> "four oceanic variables of interest"

l 74: "set-ups" -> "set-up"

l 112: "The characterization of each observation point relies on four indicators defined from the environmental variables:": I'd suggest: "Each observation point is characterized by four indicators which are based on the following environmental variables:"

l 123: "according to temporal variation relative to annual median threshold overshooting" -> "based on temporal variations of primary production exceeding a threshold based on its annual median"

l 128: "and regimes boundary values" -> "and regime boundary values"

l 131: remove the "a"

l 132: "values" sounds like k-means works only with 0-dimensional scalars, I would suggest to use "points" instead.

l 132: "separates N values in a given number of cluster by minimizing the distance of each value to the mean ..." -> "divides N points into a given number of clusters by minimizing the distance of each point to the mean ..."

l 133: Use n in this sentence so it is unambiguous: the number of clusters is chosen in advance. Then in the next sentence change "leads to" to "produces".

l 137: What is meant by "class" here? Please rephrase.

l 153: "The reference simulation" -> "The nature run"

l 153: "The goal is to retrieve back" I would suggest to change it to "The goal is then to retrieve"

l 165: The treatment of temperature is a bit tricky here as (1) the Celsius scale has a somewhat arbitrary zero-point and using Kelvin would probably lead to vastly different results and (2) how are negative temperature values dealt with? A little more information is needed and please mention the temperature units here.

l 173: I don't know if readers will immediately know what an "assimilation module" is. Maybe describe it e.g. using "used here to estimate model parameters from observations".

l 179: "in" -> "from" and "constructed as explained" -> "introduced" or "described"

l 181: "and is" -> "and it is"

l 189: "We assume 400 observations" -> "We use 400 observations in our experiments" or "We assume 400 observations were collected"

l 207: "are discussed" -> "are also discussed below"

l 230: Minor point: here section 2.2 is referred to as "subsection", previously "section" was used.

l 233: I suggest to remove the "intersection", it is confusing. But do each of the 21 configurations contain less than 0.5% of the total or doe they contain less than 0.5% together?

l 235: "The first three groups of Experiments 1a-b, 1c-d and 1e-f are meant" -> "The purpose of the first three groups of Experiments 1a-b, 1c-d and 1e-f is"

l 236: There is a sudden switch to future tense ("will").

l 249: "currents" -> "current"

l 256: "is" -> "are"

l 263: Not contradictory to the experiments themselves but the conclusions that were just drawn from these experiments!

l 264: "Despite this, it has been fixed "polar regime", the temperature in configuration C' is on average lower (−0.7C) than the temperature of configuration C'' (2.1C) (Figure 4)." -> "While both configurations are considered to be in the "polar regime", the temperature in configuration C' (−0.7C) is on on average lower...". Note that I moved the "(−0.7C)", otherwise the reader may think that configuration C' is on average −0.7C lower.

l 267: "conclude on" -> "assess"

l 269: "In the following, although distribution along secondary variables are not always shown, they have always been used in the analysis to check that the OSSE results are not biased by this type of difference between the distributions of randomly selected datasets."
I would suggest: "Although the distributions of the secondary variables are not always shown in the following experiments, they have been examined to ensure that the OSSE results are not biased by systematic differences in the secondary variables."

l 271: "such" -> "significant"

l 292: "always" -> "again"

l 305: "conclusions" -> "the conclusions"

l 307: But the bloom index appears to have little effect in Exp 4a and b, so what is the message here? It would be good for the reader to more clearly state the results.

l 350: "discussing" I'd suggest to use "examining" to avoid a double discussion.

l 352: "term" -> "terms"

Eq. 10 + 11: The notation is confusing. Is P the sum of all P_i? Mention what P_i is. Why use different notations: P_i(\tau=0) but P|_{\tau=0}?

l 362: There is something missing here: It should be the ratio of x and y. The second part, y, is missing in this sentence.

l 363: Use "night" and "day" in Eq 11 or switch to "n" and "d" here.

l 364: I think some of this information would be useful in the introduction to give readers who are not that familiar with this type of model the basic idea of how the model works early on.

l 366: "Then" -> "Second" (unless that is not yet the second main mechanism)

l 369: "Therefore..." This sentence is difficult to understand: I don't think "will be as close as" is right here, the authors probably mean to say "will contain more information about"

l 376: "is to induce" -> "is that it induces"

l 382: "biomass. This is consistent" -> "biomass, and is consistent"

l 388: "characteristics time" -> "characteristic timescale"

l 416: "Sensitivity study" -> "Conducting a sensitivity analysis"

l 417: "on" -> "of"

Fig. 2: It would be nice to include the variable in the label for each panel, e.g. "a) temperature"

Fig. 3: It is nice to see all panels together in one Figure! I would recommend changing the maximum y-limit in panel a to 18 to make the scales comparable.

Fig. 6: "associated to" -> "associated with"

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ED: Publish subject to minor revisions (review by editor) (28 Dec 2019) by Ciavatta Stefano

AR by Audrey Delpech on behalf of the Authors (07 Jan 2020) Author's response Manuscript

ED: Publish as is (10 Jan 2020) by Ciavatta Stefano

AR by Audrey Delpech on behalf of the Authors (16 Jan 2020) Author's response Manuscript

Short summary

Micronekton is an important, yet poorly known, component of the trophic chain, which partly contributes to the storage of CO₂ in the deep ocean thanks to biomass vertical migrations. In this study, we characterize the ideal sampling regions to estimate the amount of biomass that undergoes theses migrations. We find that observations made in warm, nondynamic and productive waters reduce the error of the estimation by 20 %. This result should likely serve for future in situ network deployment.