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: H. H. Zimmermann, K. R. Stoof-Leichsenring, S. Kruse, J. Müller, R. Stein, R. Tiedemann, U. Herzschuh
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-09-01
• Series: Ocean Science
• Online Access: https://os.copernicus.org/articles/16/1017/2020/os-16-1017-2020.pdf

<p>The Fram Strait is an area with a relatively low and irregular distribution of diatom microfossils in surface sediments, and thus microfossil records are scarce, rarely exceed the Holocene, and contain sparse information about past richness and taxonomic composition. These attributes make the Fram Strait an ideal study site to test the utility of sedimentary ancient DNA (<i>sed</i>aDNA) metabarcoding. Amplifying a short, partial <i>rbcL</i> marker from samples of sediment core MSM05/5-712-2 resulted in 95.7&thinsp;% of our sequences being assigned to diatoms across 18 different families, with 38.6&thinsp;% of them being resolved to species and 25.8&thinsp;% to genus level. Independent replicates show a high similarity of PCR products, especially in the oldest samples. Diatom <i>sed</i>aDNA 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 suggests several reorganisations – after the Last Glacial Maximum, after the Younger Dryas, and after the Early and after the Mid-Holocene. Different sequences assigned to, amongst others, <i>Chaetoceros socialis</i> indicate the detectability of intra-specific diversity using <i>sed</i>aDNA. We detect no clear pattern between our diatom <i>sed</i>aDNA record and the previously published IP<span class="inline-formula">₂₅</span> record of this core, although proportions of pennate diatoms increase with higher IP<span class="inline-formula">₂₅</span> concentrations and proportions of <i>Nitzschia</i> cf. <i>frigida</i> exceeding 2&thinsp;% of the assemblage point towards past sea-ice presence.</p>