Palaeoceanographic changes in Hornsund Fjord (Spitsbergen, Svalbard) over
the last millennium: new insights from ancient DNA

Pawłowska, Joanna; Zajączkowski, Marek; Łącka, Magdalena; Lejzerowicz, Franck; Esling, Philippe; Pawlowski, Jan

doi:https://doi.org/10.5194/cp-12-1459-2016

Articles | Volume 12, issue 7

https://doi.org/10.5194/cp-12-1459-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/cp-12-1459-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 12, issue 7

Research article

|

11 Jul 2016

Research article |

| 11 Jul 2016

Palaeoceanographic changes in Hornsund Fjord (Spitsbergen, Svalbard) over the last millennium: new insights from ancient DNA

Joanna Pawłowska, Marek Zajączkowski, Magdalena Łącka, Franck Lejzerowicz, Philippe Esling, and Jan Pawlowski

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Final revised paper (published on 11 Jul 2016)
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Preprint (discussion started on 13 Aug 2015)
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Interactive discussion

Status: closed

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

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RC C2035: 'review Pawłowska15 ancient DNA', Sergei Korsun, 18 Oct 2015
- AC C2822: 'Response to Referee#1: S.Korsun', Joanna Pawłowska, 04 Jan 2016
RC C2563: 'Review', Anonymous Referee #2, 05 Dec 2015
- AC C2834: 'Response to Referee#2', Joanna Pawłowska, 04 Jan 2016

Peer-review completion

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

ED: Reconsider after major revisions (16 Jan 2016) by Luc Beaufort

AR by Joanna Pawłowska on behalf of the Authors (01 Feb 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (17 Feb 2016) by Luc Beaufort

RR by Sergei Korsun (21 Mar 2016)

Suggestions for revision or reasons for rejection

The authors have provided detailed responses to all my comments. The changes made in response to a half of the general comments are largely verbal, and the authors, in effect, retain the sense of the first submission. It is Ok. The authors have invested a lot of effort into this work and have the right, I believe, to keep their interpretation. Yet, changes associated with two comments should be more specific, namely, (1) age control and (2) a brief description of the results of the previous paper.

1. There are 11 radiocarbon dates for this core (Table 1). The uppermost post-bomb date seems reliable and indicates a modern age of the top of the core. And the pair of nearly identical dates from the lowest part of the core (166 and 173 cm) also seem reliable and indicate an age of c. 600 cal. yr BP for the catcher section. There is one obviously redeposited sample (33 cm), which is naturally disregarded. The remaining seven dates (48 cm through 122 cm) range chaotically between c.300 cal. yr BP and c.100 cal. yr BP. Instead of explaining explicitly how they deal with the age scatter, the authors prefer to use obscure wording. The statement “Four of the 11 samples were in chronological order” is misleading. This wording creates impression that the sequence of dates is something naturally occurring in the data set. In fact, the authors arbitrary picked out two samples (70 and 122 cm) from the scatter of seven samples (48-122 cm) to make up a believable age model. They could have picked another pair of samples or a single sample out of the scatter 48-122 cm and still have a chronological order (less believable though). The authors should either explain explicitly which way the two selected samples (70 and 122 cm) were of better quality than the five discarded ones, or say explicitly that the choice of the two samples was a guess (the wording of course should be mild). A reference to the previous paper is not sufficient, as the Chronology section of that paper lacks relevant information. In addition, the authors hide the scale of the age issue saying that the data “should be used with caution” only from the intervals densely packed with detected age inversions (p.9 line 18), implying that similar-size intervals lacking any dates have normal deposition by default. No. The scatter compromise the whole mid part of the record, and the chronology of the whole interval between c.20 cm and c.150 cm is questionable or at least imprecise, unless the authors provide evidence that the two selected dates (70 and 122 cm) are more reliable than the others (see above). It would be fair to show all dates including discarded ones on an age-model plot (e.g. Fig. 2).

2. This paper focuses on the monothalamid part of the foraminiferal assemblage, whereas the previous paper (Pawłowska et al. 2014) reported the findings on the hard-shelled foraminifera. Naturally, before reading about non-fossilizable monothalamids, the reader expects to see a brief summary of the match between the hard-shell fossil record and the aDNA array. The reader should not be expected to rummage through the previous paper for the relevant summary; all the more so, because such a relevant summary is absent there. The revised manuscript provides a summary: “The study showed that the aDNA record detected most of the species reported for Hornsund from previous micropalaeontological investigations, including the species that dominate the fossil assemblage … However, the number of aDNA sequences read and fossil specimens differed considerably” (p.4 line 20). In my opinion, this summary is not informative. And this summary conflicts with the data in saying that all dominant fossil species were detected in aDNA. Be specific. Provide numbers. The following information perhaps should be included: the number of fossil species and the number of them detected by aDNA; the list of fossil dominants and which of them showed minor frequencies in aDNA and which of them were missing puzzlingly in the aDNA record. I believe it would be convenient for the reader if the level of match or mismatch between the frequencies of the fossil dominants and the aDNA reads is characterized numerically.

3. The coordinates of the core would better be removed from the map (Fig. 1) and placed either in the figure caption or in the Material.

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ED: Publish subject to minor revisions (review by Editor) (24 May 2016) by Luc Beaufort

AR by Joanna Pawłowska on behalf of the Authors (03 Jun 2016) Author's response Manuscript

ED: Publish as is (22 Jun 2016) by Luc Beaufort

AR by Joanna Pawłowska on behalf of the Authors (22 Jun 2016) Author's response Manuscript

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Short summary

The presented study focuses on the last millennium of the palaeoclimatic history of Svalbard region. The investigation was based on classical palaeoceanographic proxies, strengthened by the analysis of ancient foraminiferal DNA in down-core sediment samples. This study is the first attempt to implement the aDNA record in the palaeoenvironmental reconstruction. The aDNA data revealed even small environmetal changes that were not evidenced in the sedimentological and micropalaeontological record.