Abstract:

Palynological analyses of 60 surface sediment samples from West Greenland margin revealed high concentrations of dinoflagellate cysts (dinocysts), particularly in the Disko Bugt area, where they reach >10⁴ cysts g⁻¹. Dinocyst assemblages are characterized by a relatively high species diversity and are dominated by Operculodinium centrocarpum, cysts of Pentapharsodinium dalei, Islandinium minutum, Islandinium? cezare, and Brigantedinium spp. On a regional scale, the overall assemblages show statistical relationships with sea-ice cover duration, primary productivity, salinity and summer-fall temperature. The cysts of Pentapharsodinium dalei, Operculodinium centrocarpum, and Spiniferites elongatus appear linked to high productivity and to characterize the late summer-fall bloom. Although Islandinium minutum and Islandinium? cezare are generally associated with a seasonally sea-ice covered environment, there is no linear relationship between their relative abundance and sea-ice concentration or duration on a regional scale, along the West Greenland margin. The abundance of these taxa primarily reflects cold and low-salinity water in the study area. Radionuclide measurements (²¹⁰Pb and ¹³⁷Cs) allow the distinction between two categories of samples, the “modern” ones likely encompassing the interval younger than 1950 CE, and the others that may be considered “sub-modern”. Statistical analyses indicate that dinocyst assemblages belonging to “modern” and “sub-modern” categories are not significantly different. Hence, the dinocyst assemblages of surface sediment samples, both “modern” and “sub-modern”, represent fluxes homogenized over a relatively long time interval, which illustrates a spatial distribution corresponding to the main gradient in oceanographic conditions. Consequently, dinocyst assemblages in surface sediments can be assumed to represent the average “modern” conditions with a sufficiently high degree of confidence for their use in environmental studies and paleoclimate reconstructions.

https://doi.org/10.1016/j.marmicro.2019.101818