Diatom Burst-Driven Silica Depletion under the Antarctic Sea Ice: Evidence from Sponge Spicules

Earlier studies have documented the role of diatoms in reducing the diversity and abundance of other silicadependent organisms, such as radiolaria. Here we hypothesize that diatom burst-driven depletion of dissolved silica (Dsi) in the Antarctic under sea-ice waters affects other silica-biomineralizing organisms. We found intense diatom-dominated, ice-edge phytoplankton bloom in the Enderby basin resulting in severe depletion of Dsi (<5 μM) under the sea ice. We also found siliceous sponge spicules within the surface sediment collected from under the Antarctic sea ice. Dominance of small style spicules (170 spicules/g sediment) under the sea ice along with dissolution seen on them, suggests DSi deficiency in the Antarctic waters. We, therefore, conclude that there is a rapid depletion of DSi due to seasonal diatom blooms under sea ice in the Antarctic waters.