Primary production of ice algae on a seasonally-ice-covered,continental shelf

Summary Ice algae samples were collected from the winter pack ice off Labrador during March 1984. The population was dominated by centric diatoms. Chlorophyll concentrations ranged from 40 to 190 mg m^–3, and particulate organic carbon from 2 to 10 g m^–3. Assimilation numbers for the ice algae ranged from 1.4 to 2.8 mg C (mg chl)^–1 h^–1 with a mean of 2.3, and were not significantly different from the assimilation numbers of the pelagic community beneath the ice. The ice algae were not photoinhibited at light intensities approaching surface light intensities. It is postulated that the dynamic nature of the ice field permits near-surface light intensities to reach the ice algae community at irregular intervals thereby suppressing photoinhibition.