Evolution of sedimentation on the continental slope of the Kronotskii Peninsula (Eastern Kamchatka) over the last 20 ka

Sedimentary Ancient DNA From the Subarctic North Pacific: How Sea Ice, Salinity, and Insolation Dynamics Have Shaped Diatom Composition and Richness Over the Past 20,000 Years

“…frigida suggest cooling and potentially an increasing influence of winter sea ice or at least drifting ice floes in the region. In support of this, grain-size analyses of this core suggest increased presence of potentially ice-rafted material (Levitan et al, 2015) and after 6 cal kyr BP the microfossil assemblage contains sea ice-associated species (Smirnova et al, 2015), whereas the sea-ice biomarker IP 25 suggests ice-free conditions (Méheust et al, 2016). Thus, sedaDNA has the potential to complement our understanding of past sea-ice distribution.…”

“…Samples for ancient DNA analyses were collected in 2018 at GEOMAR, Kiel, in a laboratory devoid of any molecular biology work. We collected a sample every ∼16 cm (but as we included samples processed in a pilot project, there are some instances where an additional sample was included) with a median temporal resolution of 240 years (Levitan et al, 2015). To avoid the contamination of the samples with modern DNA, sampling was performed from the oldest to the youngest samples while wearing a plastic coverall, face mask, hair net.…”

“…frigida of more than 3% in this phase are not necessarily contradictory. While the absence of IP 25 suggests ice-free conditions, gravel-sized ice-rafted debris at about 13.86 cal kyr BP (560 cm depth; Levitan et al, 2015) points toward the presence of sea ice. As Nitzschia frigida is a common inhabitant of landfast ice communities (Medlin & Hasle, 1990), a possible explanation could be the occurrence of drifting ice floes, which were transported away from the coast or southward by the East Kamchatka Current, and probably originated from enclosed bights and bays along the eastern coast of Kamchatka (Polyakova, 2007).…”