Taxonomical notes and ecological requirements of Holocene arctic diatoms collected on Bellsund Drift, Fram Strait (Svalbard)

Diatoms are important proxy for paleo-environmental reconstruction. They are sensible to minimum change of physical (temperature, salinity, sea ice, etc.) and chemical (nutrient, silica dissolution, etc.) parameters. For this reason, they represent an excellent instrument to study (paleo)environments and climate change. We present a brief taxonomical description and the ecological requirements of 18 diatom species belonging to 14 genera identified in the Holocene interval of the marine sediment core GS191-01PC, which was retrieved from the Bellsund Drift, on the eastern side of the Fram Strait. Analysis on the investigated sequence highlights that the most common species is Coscinodiscus marginatus that in the Arctic area, is associated with warm temperate Atlantic Water. Other common species are Paralia sulcata, Rhizosolenia hebetata, and Thalassiosira antarctica var. borealis. P. sulcata is a thycopelagic species associated with warm-temperate water. R. hebetata and T. antarctica are cold water indicators. All species have been measured for a morphometric comparison with other taxonomic work in the adjacent areas. The results are that some diatoms found in the studied area are smaller than in the other regions (different morphometric data could be due to the environmental condition). This study allows to recognize the principal ecological group of the diatoms assemblage present in Bellsund Drift: the sea-, the cold water group, warm-temperate water indicators and fresh-water group, represented by Aulocoseira spp. This review would contribute to the knowledge of the taxonomy and the ecological preferences of the arctic taxa to help/infer a robust interpretation of Bellsund drift paleo-environmental evolution.