Planktonic foraminifera genomic variations reflect paleoceanographic changes in the Arctic: evidence from sedimentary ancient DNA

Joanna Pawłowska,Marek Zajączkowski,Jutta E Wollenburg,Jan Pawlowski

doi:10.1038/s41598-020-72146-9

Abstract

Deciphering the evolution of marine plankton is typically based on the study of microfossil groups. Cryptic speciation is common in these groups, and large intragenomic variations occur in ribosomal RNA genes of many morphospecies. In this study, we correlated the distribution of ribosomal amplicon sequence variants (ASVs) with paleoceanographic changes by analyzing the high-throughput sequence data assigned to Neogloboquadrina pachyderma in a 140,000-year-old sediment core from the Arctic Ocean. The sedimentary ancient DNA demonstrated the occurrence of various N. pachyderma ASVs whose occurrence and dominance varied through time. Most remarkable was the striking appearance of ASV18, which was nearly absent in older sediments but became dominant during the last glacial maximum and continues to persist today. Although the molecular ecology of planktonic foraminifera is still poorly known, the analysis of their intragenomic variations through time has the potential to provide new insight into the evolution of marine biodiversity and may lead to the development of new and important paleoceanographic proxies.

Highlights

Deciphering the evolution of marine plankton is typically based on the study of microfossil groups
Sequences were clustered into 42,329 Amplicon Sequence Variants (ASVs) with 143 of them containing more than 1,000 reads (Table 1)
Molecular systematics of planktonic foraminifera focused on distinction of cryptic species, called “genetic types” or “genotypes” that have been observed in almost every m orphospecies[11]

Summary

Introduction

Deciphering the evolution of marine plankton is typically based on the study of microfossil groups. Recent metabarcoding studies from water and surface sediments have confirmed the large genetic diversity of planktonic foraminifera, which significantly exceeds the number of their m orphotypes[13,14] This is evident in small-sized foraminifera, whose ecological importance is often u nderestimated[14]. SedaDNA metabarcoding analyses have been applied to deep-sea sediments of the South Atlantic dating back to 35 ka, which revealed a high diversity of foraminifera and radiolarians[18]. This is the first study to investigate the composition of Arctic planktonic foraminifera in sedaDNA samples

Methods

Results

Conclusion