Assessing the passive dispersal of benthic foraminifera through environmental <scp>DNA</scp>

Abstract Passive dispersal plays a key role in the distribution of marine benthic species that have reduced mobility and lack planktonic life stages. However, its qualitative and quantitative importance, as well as the ecological and environmental factors responsible for it, remain largely unknown. Here, we address these issues by analyzing the dispersal of benthic foraminifera using environmental DNA ( e DNA) from the water column and sediment samples collected at 24 stations in the Nordic Seas. Our results show that water e DNA contains large amounts of benthic foraminiferal DNA. Approximately 41.5% of the foraminiferal Amplicon Sequence Variants (ASVs) found in the sediment were also present in the water samples, with over 22.1% shared among samples from the ocean surface, at 100 m water depth, and in the sediment. However, not all benthic foraminiferal taxa were equally represented in the water samples. The calcareous species (mainly rotaliids) are more frequently observed in surface water. Our study suggests that some benthic foraminifera are likely dispersed over long‐distance transport, traversing distances of hundreds of kilometers. Dispersal patterns depend on species' habitat and water circulation patterns, with shallow‐water species being preferentially transported by surface water currents and deep‐sea species primarily carried by bottom‐water currents. This work highlights the importance of passive dispersal in shaping the biogeography of benthic protists and underlines the value of e DNA metabarcoding for studying connectivity in marine ecosystems.