Utility of foraminifera environmental DNA as proxies in relative sea-level reconstructions from Northern Norway

Foraminifera are commonly applied in saltmarsh and mangrove reconstructions of relative sea level (RSL) due to their distinct vertical zonation with respect to tidal elevation. The success of this approach relies on deriving accurate foraminifera counts that are representative of the true foraminifera assemblage. However, traditional counts using the microscope can be time consuming, and taphonomic processes may lead to poor preservation of foraminifera tests, hindering identification. This study explores a novel approach that compares traditional foraminifera analyses with environmental DNA (eDNA) metabarcoding to assess the utility of foraminifera eDNA as proxies to reconstruct past RSL. We collected paired samples for traditional foraminifera counts and eDNA metabarcoding from an Arctic saltmarsh near the community of Kongsfjord in Finnmark, northern Norway. Samples were collected along a transect across the modern saltmarsh surface and at successive depths within the fossil saltmarsh sequence. Our metabarcoding targets the 18S rRNA gene’s variable region 37f that are specific to foraminifera. Preliminary findings reveal differences between the foraminifera assemblage determined using traditional microscope methods versus foraminifera metabarcoding, with certain species of foraminifera that were uniquely identified with the eDNA approach. This study demonstrates the utility of foraminifera metabarcoding to complement traditional morphology-based counts and paves the way for wider application of foraminifera metabarcoding in palaeoenvironmental research.