Distribution of common modern dinoflagellate cyst taxa in surface sediments of the Northern Hemisphere in relation to environmental parameters: The new n=1968 database

We present a new version of the standardized Northern Hemisphere “modern” dinoflagellate cyst (“dinocyst”) database, which includes abundances of 71 taxa at 1968 sites across the Northern Hemisphere, cross-referenced with 17 environmental parameters extracted mostly from the 2013 World Ocean Atlas. Several taxa with tropical to warm temperate affinities were added to the previous database version. Dinocyst concentrations in the surface sediments reach 10⁶ cysts g⁻¹, with maximum values along the continental margins and minimum values offshore in distal open ocean settings. Assemblages are characterized by the co-occurrence of phototrophic (n = 41) and heterotrophic taxa (n = 30), with maximum proportions of heterotrophic taxa in high productivity regions, notably at the sea-ice edge and in upwelling regions. The main pattern of assemblage distributions includes north–south and nearshore–offshore gradients, with maximum diversity of species along the continental margins and towards the south, in warm temperate and tropical areas. Canonical correspondence analyses performed on heterotrophic and phototrophic taxa independently yield consistent results, hence suggesting similar, but not identical, ecological affinities for both taxonomic groups. For both groups, sea-surface temperature and sea-ice are the most determining parameters, but the phototrophic taxa seem more sensitive to onshore–offshore gradients marked by salinity changes. Productivity-related parameters also determine dinocyst distribution, especially primary productivity in the fall and winter, with a stronger relationship for the combined dataset of phototrophic and heterotrophic taxa.