Paleoenvironments in the Fram Strait during Marine Isotope Stages 2–6 based on planktonic paleobiological and stable-isotope proxies and ice-rafted debris

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

“…The sequences were processed, filtered, and assigned a taxonomic name according to the NCBI taxonomy using the OBITools package (Boyer et al, 2016) with the same bioinformatics parameter settings as described in Dulias et al (2017). We refrained from clustering sequences into operational taxonomic units and used amplicon sequence variants (ASVs) as recommended by Callahan et al (2017). The OBITools program obiclean can identify ASVs that have likely arisen due to PCR or sequencing errors.…”

“…Their dominance is likely the result of high paleoproductivity or of differential overrepresentation caused by preservation and/or technical biases. Indeed, in the Fram Strait, Chaetoceros and Thalassiosira species especially have high productivity in different hydrographical regimes (Gradinger and Baumann, 1991;Lalande et al, 2013) as well as at Kongsfjorden, a major outlet of western Svalbard potentially influencing the coring site (Hodal et al, 2012), and even in micropaleontological studies they are often dominant (Birks and Koç, 2002;Bylinskaya et al, 2016;Oksman et al, 2017Oksman et al, , 2019. Next to high paleoproductivity, the preservation of sedaDNA could be biased by differential degradation.…”

“…It is conceivable that a heterogeneous and dynamic environment produced by winter sea-ice cover with ice-free conditions during summer could allow diverse diatom communities to develop in the different habitats and over the seasons, which is suggested by the highest overall numbers of ASVs in samples dated to this time span. Thalassiosira and Chaetoceros are also abundant in the LGM microfossil assemblage identified further south at the Knipovich Ridge (eastern Fram Strait), although species of the genera Rhizosolenia and Cos-cinodiscus are strongly represented there as well (Bylinskaya et al, 2016).…”

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

“…Their dominance is likely the result of high paleoproductivity or of differential overrepresentation caused by preservation and/or technical biases. Indeed, in the Fram Strait especially Chaetoceros and Thalassiosira species have high productivity in different hydrographical regimes (Gradinger and Baumann, 1991;Lalande et al, 2013) as well as at Kongsfjorden, a major outlet of western Svalbard potentially influencing the coring site (Hodal et al, 2012), and even in micropaleontological studies they are often dominant (Birks and Koç, 2002;Bylinskaya et al, 2016;Oksman et al, 2017Oksman et al, , 2019. Next to high paleo-productivity, the preservation of sedaDNA could be biased by differential degradation.…”

“…Author(s) 2019. CC BY 4.0 License.in the LGM microfossil assemblage identified further south at the Knipovich Ridge (eastern Fram Strait), although species of the genera Rhizosolenia and Coscinodiscus are strongly represented there as well(Bylinskaya et al, 2016).CONISS assigned samples dated to the deglacial phase to zone II, despite their representation of extremely different climatic intervals. The samples thus show highly variable taxonomic composition.…”