Sinking rates of natural phytoplankton assemblages in marginal ice zones

Sinking rates of natural phytoplankton assemblages were measured for the first time in marginal ice zones of the Weddell Sea and the East Greenland Sea using a homogeneous sample method. Rates were generally lower in the Greenland Sea than in the Weddell Sea. Phytoplankton assemblages from pycnoclines sank slower than those from the surface although differences in seawater density and viscosity could account for no more than 5% of the observed differences, which were usually > 35%. Size fractionation experiments showed that particles > 20 μm sank faster than those < 20 μm. There were no significant correlations of sinking rates with physical characteristics of the water column (temperature, salinity, density), nutrient concentrations (nitrate, silicate), or light incidence during the experiments. Sinking rates in marginal ice zones fall within the range reported for other areas of the ocean.