Platelet ice

Forming mostly in the Antarctic, platelets are discs of ice which are found when the water flowing under the land fast ice becomes super cooled (Leonard et al., 2006). The platelets are being formed at of up 250m (Penrose et al., 1994), which then rise up the water column to form dense clouds under the sea ice that can be up to 20m thick. The platelets accumulate, trapping seawater between them.

Between the platelet layer and the fast ice there are large communities of algae and bacteria. At times the nutrient levels may become the limiting factor, life is still abundant due to high levels of chlorophyll and protection from grazers inbetween the ice crystals. It seems light should be the limiting factor in the platelet layer as at this depth it is at 3 % of its surface levels, but on the contrary as the photosynthetic algae are saturated by only 10 µmol photons mˉ² s¹so only (Thomas et al 2008). Large concentrations of algae are mainly seen here due to the massive surface area the platelets provide. Also due to the fact the cloud of platelets is not solid fresh water is pushed through it, replenishing all of the nutrients. Platelet ice has been linked to be a mechanism for organisms to colonize the ice above. As in theory organisms can use the platelet to lift them up to the ice above. This could not be the main transport for organisms as it only forms in localised areas, and in no way can be the main process (Thomas et al. 2008).

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