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

We traced diatom composition and diversity through time using diatom-derived sedimentary ancient DNA (sedaDNA) from eastern continental slope sediments off Kamchatka (North Pacific) by applying a short, diatom-specific marker on 63 samples in metabarcoding approach. The sequences were assigned to diatoms that are common the area characteristic of cold water. SedaDNA allowed us observe shifts potential lineages species genus Chaetoceros can be related different climatic phases, suggesting pre-adapted ecotypes might have played role long-term success areas changing environmental conditions. These sedaDNA results complement our understanding history assemblages their general relationship conditions past. Sea-ice (Pauliella taeniata [Grunow] Round & Basson, Attheya septentrionalis [Østrup] R. M. Crawford Nitzschia frigida [Grunow]) detected during late glacial Younger Dryas agreement with previous sea-ice reconstructions. A positive correlation between pennate richness proxy IP25 suggests sea ice fosters richness, whereas negative June insolation temperature points unfavorable Holocene. sharp increase proportions freshwater at ∼11.1 cal kyr BP implies influence terrestrial runoff coincides loss 42% sequence variants. assume reduced salinity this stabilized vertical stratification which limited replenishment nutrients euphotic zone.