Spatial and temporal distribution of planktonic protists in the East Greenland fjord and offshore waters

Abstract

Summer planktonic protist assemblages (>20 μ m) were investigated in the East Greenland Young Sound fjord and offshore waters between 2009 and 2012. Samples were taken using 20 μ m mesh nets and Niskin bottles, fixed in acidic Lugol's solution, and analysed by microscopy. Comparison between the 2 methods showed that important colonial species present in net haul samples were not present in the water bottle samples. In Young Sound waters, the planktonic protist taxa varied significantly, corresponding to temperature and salinity gradients driven by runoff from the Greenland Ice Sheet. Fjord waters were characterised by diatoms and colonial chrysophyte species associated with meltwater (sea ice) and freshwater (snow and ice) input. Time series data from Young Sound showed inter-annual variations among the planktonic protist taxa due to dynamic water exchange between the inner and outer fjord. Little spatial variation among taxa was observed in offshore waters, which were characterized by diatoms, silico-flagellates, and dinoflagellates. Different diatom compositions were observed in the shelf area dominated by the cold East Greenland Current and in the warmer Atlantic waters of the Mid Denmark Strait. Silicoflagellates characterised sub-surface water masses of the Greenland Sea, which were influenced by saline oceanic waters, possibly Modified Atlantic Water. Our study shows that summer planktonic protist assemblages varied along the East Greenland coast due to freshwater inputs, sea ice melt, and Polar and Atlantic water circulation.