Ancient DNA complements microfossil record in deep-sea subsurface sediments

Deep-sea subsurface sediments are the most important archives of marine biodiversity. Until now, these archives were studied mainly using the microfossil record, disregarding large amounts of DNA accumulated on the deep-sea floor. Accessing ancient DNA (aDNA) molecules preserved down-core would offer unique insights into the history of marine biodiversity, including both fossilized and non-fossilized taxa. Here, we recover aDNA of eukaryotic origin across four cores collected at abyssal depths in the South Atlantic, in up to 32.5 thousand-year-old sediment layers. Our study focuses on foraminifera and radiolaria, two major groups of marine microfossils also comprising diverse non-fossilized taxa. We describe their assemblages in down-core sediment layers applying both micropaleontological and environmental DNA sequencing approaches. Short fragments of the foraminiferal and radiolarian SSU rRNA gene recovered from sedimentary DNA extracts provide evidence that eukaryotic aDNA is preserve...