EGU2020-5444, updated on 17 Dec 2021
https://doi.org/10.5194/egusphere-egu2020-5444
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Ancient plant DNA, macro- and microfossil studies of the lake sediments from the High Arctic lake Tenndammen, Svalbard

Anastasia Poliakova1, Lena M. Håkansson2, Anders Schomacker3, Sandra Garces Pastor1, and Inger Greve Alsos1
Anastasia Poliakova et al.
  • 1Tromsø University Museum, UiT - The Arctic University of Norway, NO-9037 Tromsø, Norway (anastasia.poliakova@uit.no)
  • 2The University Centre in Svalbard (UNIS), Svalbard Science Centre, P.O. Box 156, N-9171 Longyearbyen, Norway
  • 3Department of Geosciences, UiT - The Arctic University of Norway, NO-9037 Tromsø, Norway

Ancient DNA metabarcoding applied together with the investigations of the plant macro-remains, pollen, spores and non-pollen palynomorphs (NPP), open new perspectives and give better taxonomical resolution, allowing to obtain more precise and specific data on the local environment conditions and their changes. So far, only three multiproxy studies that involve both molecular and palaeobotanical/palynological methods are available for the high Arctic archipelago Svalbard. We intend to contribute filling this gap. Therefore, a field trip to Svalbard was undertaken in September, 2019, and three sediment cores were retrieved from the Tenndammen lake (N 78°06.118; E 15°02.024, 7 m asl) which is a small and shallow water body (ca 2.5 m depth). The lake is located in the valley of Colesdalen, a well-known Svalbard’s biodiversity hot spots and a home for about seven to ten thermophilic plant species.

To investigate the Holocene to modern vegetation history of this place, the 85cm core Te2019 was chosen, it was described for lithology, X-rayed, µXRF-scanned, line-scan photographed with high resolution and sampled for sedaDNA, pollen, spores and NPP studies as well as for studies on plant macrofossils. Ten 14C AMS dates were taken in order to establish an age-depth model. The DNA record contains around 100 taxa, most findings of those are supported by pollen studies (Asteraceae, Betula, Brassicaceae, Salix, Saxifraga, Vaccinium/Ericaceae) and by spores (Equisetum and Bryophyta). In addition, various fungi spores were identified. Investigations of plant macro-remains well support findings of the aquatic (i.e. Warnstorfia fluitans) and terrestrial mosses (e.g. Aulacomnium conf. turgidum, Bryum spp., Distichium capillaceum, Calliergon richardsonii, Scorpidium cossonii, Sphagnum spp., Rhizomnium spp.). Besides, fragments of Salix and Betula leaves and fruit parts, various leaf, stem tissues and flower fragments of Saxifraga species were found within the samples from the same depths with the correspondence to DNA records. Three DNA zones (SvDNA 1 – SvDNA3) and  one subzone within the earliest zone (SvDNA-1a – SvDNA-1b) were established. Relations between DNA, pollen and macrofossil zones were studied. This study is performed within the “Future ArcTic Ecosystems” (FATE) research program: Initiative for investigation on drivers of diversity and future scenarios from ethnoecology, contemporary ecology and ancient DNA.

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  • CC1: Comment on EGU2020-5444, Kathleen Stoof-Leichsenring, 05 May 2020

    Dear Anastasia,

    I have some questions, that I could not ask yesterday in teh live chat. In the bar plot you mention a lot of Exotic taxa: What are exotic taxa in the macrofossil record? Where do they come from? Is it a matter of the low taxonomic resolution ? Do exotic taxa in the aDNA record relate to contaminations by modern plant DNA through lab chemicals or other contamination sources? 

     

    Thanks Kathleen

    • AC1: for Kathleen Stoof-Leichsenring, Anastasia Poliakova, 05 May 2020

      Dear Kathleen,

      I am happy that my EGU2020 contribution has attracted your attention. First of all, let me explain what I call “exotics”. These are taxa that are not seen in/known from the local and regional vegetation. I am agree that it is rather odd to speak about “exotic macrofossils”. All my “exotics in macrofossil” are remains of pine and spruce, trees obviously absent in tundra vegetation communities. Those tissue fragments come from the construction wood of the building remains left within the study area. There used to be a coalmine and a miner’s settlement in the Colesbukta before its closing in 1988.  

      The taxonomic resolution in this study I would not call that low. Plant macrofossil study solely detected about 2,600 plant remains that belong to 44 taxa (24 herbs and 7 bryophytes among them). Many of herbs and bryophytes, all shrubs and dwarfs were identified to the species level. I was lucky to find a number of seeds and identifiable tissues, in few cases – even fragments of flowers, which is exiting. This high diversity is a rare case in the Arctic! - In my practice at least. Pollen analysis revealed 48 pollen and 4 spore types (among them 12 exotic types, i.e. long distance component). aDNA data after the final filtering left me with sequences assigned to 48 vascular plants (1 shrub which is Salix cf. polaris, 29 herbs, 16 sedges, rushes and grasses, 2 Equisetum types) plus 60 bryophytes, which is a lot compare to other sites in Svalbard and Northern Norway, and 4 algae additionally – 112 different taxa in total. Roughly in about 30% of cases aDNA types and pollen types were assigned to species, although most of them - to genus or to several genera. Taxa assignment was performed using 2 plant DNA databases of about 2000 species. Pollen and/or macro remains obtained from the same samples of the same depth support many of the findings in aDNA. I dare to say that it is a good record.

      As for the exotic taxa in the aDNA record, you are right, I think. They should relate to contamination by modern plant DNA through the lab chemicals, most of them are found in the negative controls and were filtered out (yet presented in the bar diagram). Other cores analyzed in the same lab with the same reagents show about the same contaminators in the negative tests. Yesterday you also asked about Betula in aDNA. Betula nana was detected there most likely as a true-positive, but did not survived the final data filtering.

      However, in some cases, finding unexcited taxa in aDNA record could be unlikely due to a contamination as I found pollen grains of them in the same samples. It might be some material brought by migrating gees, or might be just random findings – this is my speculation unsupported by any data, very arguable but still interesting. In the final aDNA dataset all exotics were filtered out.

      I hope that I answered your questions and you will not get bored just after looking at this bulky text. Thank you once again and take care. Let us believe that one day there will be a chance for us to talk in person.

      Anastasia