Ecology and Hydrography of Sea Ice and the Water Column in Lagoon Notoro-ko during Frozen Period

Abstract

Lagoon Notoro-ko is connected to the Okhotsk Sea by an artificial channel, and it has few incoming rivers. The lagoon is covered with sea ice during the winter and early spring. We investigated temporal changes in environmental variables in the sea ice and water column from February 6^th to March 18^th 2008. The integrated chlorophyll α in water column was remarkably high on every survey day, ranging from 8.7－119.1 mg·m^-2, whereas in the sea, it ranged from 2.5－11.6 mg·m^-2. In contrast, chlorophyll a concentrations (relative to unit volume) in the sea ice and water column were 8.3－40.1 mg·m^-3 and 0.4－6.0 mg·m^-3, respectively. Chlorophyll a concentration was therefore remarkably high in the sea ice, with the maximum concentration of chlorophyll a in sea ice detected in the lower layer. We suggest that the sea ice gathers chlorophyll a in the lower layers, and it is thus likely that sea ice provides the environment which small amount of chlorophyll a is available to primary consumers easily.