EGU2020-10928
https://doi.org/10.5194/egusphere-egu2020-10928
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

A sedimentary ancient DNA approach to elucidate the Labrador Sea paleoceanography over the last ~130,000 years

Stijn De Schepper1, Jessica Louise Ray2, Lisa Griem3, Nicolas Van Nieuwenhove4, Danielle Magann Grant1, Kristine Steinsland1, Katrine Sandnes Skaar2, and Umer Zeeshan Ijaz5
Stijn De Schepper et al.
  • 1NORCE Climate, Norwegian Research Centre and Bjerknes Centre for Climate Research, Bergen, Norway (stde@norceresearch.no)
  • 2NORCE Environment, Norwegian Research Centre, Bergen, Norway
  • 3Department of Earth Science, University of Bergen and Bjerknes Center for Climate Research, Bergen, Norway
  • 4Department of Earth Sciences, University of New Brunswick, Fredericton, Canada
  • 5School of Engineering, University of Glasgow, Glasgow, United Kingdom

Long sedimentary ancient DNA (sedaDNA) records from the marine environment are at present a curiosity and their utility in paleoceanographic research is not yet fully explored. Nevertheless, a few studies indicate that this ecogenetic repository represents an untapped source of new information with which paleoclimatic and paleoceanographic variability can be more deeply explored. We have generated a sedaDNA record from a 19.6 m-long sediment core in the Labrador Sea (Eirik Drift, south of Greenland). The record extends from the early Holocene to Marine Isotope Stage 5 (ca. 130,000 years ago), and we characterized several important climatic transitions in this time interval using stable isotope stratigraphy, ice-rafted detritus counts, and dinoflagellate cyst census counts. The primary goal of this investigation was to query the sedaDNA record for a biological indication of the last and penultimate deglaciation, as well as Heinrich events identified between 65,000 and 25,000 years ago. Our metabarcoding strategy targeted a broad diversity of eukaryotic organisms through amplification of the V7 hypervariable region of the small subunit ribosomal RNA (SSU rRNA) gene. The preliminary sedaDNA results indicate that eukaryote ancient DNA is present in all samples investigated, including those dating back to Marine Isotope Stage 5. Furthermore, we identified abundance shifts in Protaspidae (cercozoa), diatoms, dinoflagellates, and marine stramenopiles (amongst others) that may be linked to changes in paleoceanography during the last two deglaciations as well as Heinrich events (HE3, HE4).

How to cite: De Schepper, S., Ray, J. L., Griem, L., Van Nieuwenhove, N., Grant, D. M., Steinsland, K., Sandnes Skaar, K., and Ijaz, U. Z.: A sedimentary ancient DNA approach to elucidate the Labrador Sea paleoceanography over the last ~130,000 years, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10928, https://doi.org/10.5194/egusphere-egu2020-10928, 2020

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  • CC1: Comment on EGU2020-10928, Charline Giguet-Covex, 04 May 2020

    Dear Stijn,

    I am not specialist of the Eemian interglacial period and I was wondering if we have any idea of the origin in the change in composition between 5e and 5d.

    Are you recording effects of the Heinrich Events on the aquatic organism composition?

    Charline Giguet-Covex

    • AC1: Reply to CC1, Stijn De Schepper, 04 May 2020

      Dear Charline,

      [Eemian question] At this time, we interpret the change in the metabarcoding record to be reflecting regional oceanographic change due to global cooling at the MIS 5e to 5d transition. Marine palynology suggests a change from Atlantic sourced surface waters, to more cooler, Arctic waters.

      [Heinrich Events question] H3, H4 and H5 show a different response in the published stable isotope and IRD records (Griem et al. 2019), in the palynology assemblage (not shown) and also in the ancient DNA metabarcodes. In the three investigated Heinrich Events, we recorded very different abundance variations of e.g. Syndiniales, Copepods, Phaeocystis, and cercozoans, amongst others. We have not yet looked into detail how they are different and what that means.

      All the best,

      Stijn

  • CC2: Comment on EGU2020-10928, Kathleen Stoof-Leichsenring, 05 May 2020

    Dear Stijn,

    I would like to know about Rhizaria preservation in your samples. I your plots I can see that you detected Rhizaria in very old marine sediment samples. Do you know about any hints concerning special preservation of Rhizaria in older samples? What do Rhizaria ecologically indicate in your record?

    Thanks

    Kathleen

    • AC2: Reply to CC2, Stijn De Schepper, 11 May 2020

      Dear Kathleen,

      Apologies for the late reply.

      I unfortunately cannot answer your preservation question at this point. We will be measuring additional samples in the coming weeks, which may shed some more light about the metabarcode composition, ecological signal and preservation across the last interglacial. If your questions refers to preservation of skeletal remains of Rhizaria: we have not looked for radiolarians; foraminifers are present throughout but we have not done assemblages studies on those.

      There is a clear change in the surface waters in MIS 5d (the cooler interval following the last interglacial), where Atlantic water is replaced by more cool, polar waters that likely also entrained a higher amount of nutrients. It is likely no coincidence that the Rhizaria are more abundant in those cooler, nutrient rich polar sourced waters. 

      I hope this was helpful.
      Stijn