Changes in the composition of marine and sea-ice diatoms derived from sedimentary ancient DNA of the eastern Fram Strait over the past 30,000 years

• Main Authors: Zimmermann, Heike H., Stoof-Leichsenring, Kathleen R., Kruse, Stefan, Müller, Juliane, Stein, Rüdiger, Tiedemann, Ralf, Herzschuh, Ullrike
• Format: Text
• Language: English
• Published: 2019
• Subjects: Fram Strait; Sea ice
• Online Access: https://doi.org/10.5194/os-2019-113; https://os.copernicus.org/preprints/os-2019-113/

The Fram Strait is an area with a relatively low and irregular distribution of diatom microfossils in surface sediments, and thus microfossil records are underrepresented, rarely exceed the Holocene and contain sparse information about past diversity and taxonomic composition. These attributes make the Fram Strait an ideal study site to test the utility of sedimentary ancient DNA ( seda DNA) metabarcoding. By amplifying a short, partial rbcL marker, 95.7 % of our sequences are assigned to diatoms across 18 different families with 38.6 % of them being resolved to species and 25.8 % to genus level. Independent replicates show high similarity of PCR products, especially in the oldest samples. Diatom richness is highest in the Late Weichselian and lowest in Mid- and Late-Holocene samples. Taxonomic composition is dominated by cold-water and sea-ice associated diatoms and shows two re-organizations – one after the Last Glacial Maximum and another after the Younger Dryas. Different sequences assigned, amongst others, to Chaetoceros socialis indicate the detectability of intra-specific diversity using seda DNA. We detect no clear pattern between our diatom seda DNA record and the previously published IP 25 record of this core, although proportions of pennate diatoms increase with higher IP 25 concentrations and proportions of Nitzschia cf. frigida exceeding 2 % of the assemblage point towards past sea-ice presence.