Deep-sea sponge grounds as nutrient sinks: denitrification is common in boreo-Arctic sponges

Rooks, Christine; Fang, James Kar-Hei; Mørkved, Pål Tore; Zhao, Rui; Rapp, Hans Tore; Xavier, Joana R.; Hoffmann, Friederike

doi:https://doi.org/10.5194/bg-17-1231-2020

Articles | Volume 17, issue 5

https://doi.org/10.5194/bg-17-1231-2020

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

https://doi.org/10.5194/bg-17-1231-2020

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

Articles | Volume 17, issue 5

Research article

|

06 Mar 2020

Research article |

| 06 Mar 2020

Deep-sea sponge grounds as nutrient sinks: denitrification is common in boreo-Arctic sponges

Christine Rooks, James Kar-Hei Fang, Pål Tore Mørkved, Rui Zhao, Hans Tore Rapp, Joana R. Xavier, and Friederike Hoffmann

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Final revised paper (published on 06 Mar 2020)
Supplement to the final revised paper
Preprint (discussion started on 24 Apr 2019)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of bg-2019-135', Anonymous Referee #1, 06 May 2019
- AC2: 'Reply to Ref 1', Friederike Hoffmann, 30 Sep 2019
RC2: 'Deep sea N cycling in sponges review', Anonymous Referee #2, 08 May 2019
- AC3: 'Reply to Ref 2', Friederike Hoffmann, 30 Sep 2019
RC3: 'review BGD-5194 denitrification in sponges', Anonymous Referee #3, 06 Jun 2019
- AC4: 'Reply to Ref 3', Friederike Hoffmann, 30 Sep 2019
AC1: 'Submission of revised manuscript', Friederike Hoffmann, 30 Sep 2019
AC5: 'Revised data set', Friederike Hoffmann, 01 Oct 2019

Peer-review completion

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

ED: Reconsider after major revisions (03 Oct 2019) by Jack Middelburg

AR by Friederike Hoffmann on behalf of the Authors (04 Oct 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (08 Oct 2019) by Jack Middelburg

RR by Anonymous Referee #3 (22 Oct 2019)

RR by Anonymous Referee #1 (29 Nov 2019)

Suggestions for revision or reasons for rejection

The manuscript has been revised substantially and my major comments to the original version have been taken into account. The revision is a substantial improvement, and the manuscript now conveys clear and justified conclusions. Importantly, the central results from 15N incubations have been revised in detail, with the discovery of critical errors in the original calculations. The revised results now appear completely plausible. I have suggestion for slight rewording, and a few points need further clarification.

p. 3 l. 4-8: “Scenario” here and later in the text is used in way that doesn’t fit with my understanding of the word, and since the authors now emphasize the potential nature of the measured rates, “scenario” is not needed. Suggestion: “The results suggest a high potential denitrification capacity… and Arctic sponge grounds, with areal denitrification rates up 0.6…for non-pumping sponges and even 0.3 mmol N m-2 d-1 for pumping sponges.”

p. 5 l. 4-6: Nitrification and denitrification don’t compete – what would they compete for?

p. 13 l. 20- p.14 l. 1 + 10-12: I am confused here: First you say that samples showing an abrupt increase were excluded even though they didn’t show visual signs of degradation, and then you say that increases represent incipient anoxia BECAUSE there were no signs of degradation – if samples with such increases were excluded, why do we hear about them later, and how can visual inspection be trusted in the 2nd case when it couldn’t in the 1st.

p. 16 l. 21: This seems to repeat l. 13 (and 15N isotopes were not produced). Also, please mention that the rates reported are D14 (at least I think they are?).

p. 19, l. 16: Instead of “0” I suggest “below detection” (and “n.d.” for the tables).

p. 20 l. 7: italics missing

p. 24 l. 19: 0 instead of O

p. 26 l. 24: In their rebuttal the authors boldly state that this is textbook knowledge and refuse to add a reference. I would be hesitant with such statements (or acknowledge that textbooks can be wrong). See, e.g., Jones et al. (2008) Mol. Biol. Evol. 25:1955-66.

p. 28 l. 10: Instead of “scenarios about the” how about “first-order estimates of”? Also, considering that numbers here are rough estimates, I would use just 1 or 2 significant digits.

Table 1: The number of significant digits should reflect the precision of the data.

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ED: Publish subject to minor revisions (review by editor) (02 Dec 2019) by Jack Middelburg

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

ED: Publish subject to technical corrections (20 Jan 2020) by Jack Middelburg

AR by Friederike Hoffmann on behalf of the Authors (28 Jan 2020) Author's response Manuscript

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Short summary

Sponge grounds are known as nutrient sources, providing nitrate and ammonium to the ocean. We found that they also can do the opposite: in six species from Arctic and North Atlantic sponge grounds, we measured high rates of denitrification, which remove these nutrients from the sea. Rates were highest when the sponge tissue got low in oxygen, which happens when sponges stop pumping because of stress. Sponge grounds may become nutrient sinks when exposed to stress.