Controls on spatial heterogeneity in dinoflagellate cyst distribution in recent sediments off West Antarctica

Here we present the study of 48 new dinoflagellate cyst assemblages from the west Antarctic shelf sediments on a wide longitudinal scale, with a greater representation of ice-proximal sites, and provide a comprehensive overview of their distributional patterns and multiple environmental forcing factors. We find a strong spatial heterogeneity in the dinoflagellate cyst distribution patterns; 1) the northern Antarctic Peninsula region is dominated by Islandinium? minutum, Selenopemphix antarctica and Brigantedinium spp. in association with meltwater-induced stratification and high diatom productivity, 2) the Bellingshausen-Amundsen Seas is dominated by Gymnodinium microreticulatum and Selenopemphix sp. 1, under influences of strong offshore winds, unstable water column and Phaeocystis blooms in austral summer, and 3) the Ross Sea shows an extreme contrast - the east-central region under vigorous vertical mixing and high Phaeocystis production is dominated by Selenopemphix sp. 1, while the western side with high sea-ice concentration and sea-ice derived meltwater stratification is dominated by Polarella glacialis cysts together with Nucicla umbiliphora, I.? minutum and Cryodinium meridianum. The robust along-shelf separations of the dinoflagellate cyst species compositions highlight melt-related hydrodynamic-meteorological coupling processes around maritime Antarctica that control physico-biological properties and overall microplankton communities therein. As the ice-shelf disintegration and sea-ice loss continue, there will be a fundamental reconfiguration of microplankton production and their community structures in a future Antarctic Ocean with greater open-water areas. This study highlights the potential of dinoflagellate cysts to monitor changes in hydrographic conditions and plankton communities in these sensitive polar marine ecosystems.