北海道東部の海跡湖能取湖における海洋環境

－水温・塩分・溶存酸素・栄養塩の動態－

抄録

Lagoon Notoro-ko is connected to the Okhotsk Sea by an artificial channel and the water mass of this lagoon is exchanged by a tidal movement and little river flows. Therefore, this lagoon is assumed a saltwater lagoon and a seasonal change of environmental conditions on this lagoon has been reflected one of the coastal waters on Okhotsk Sea. In order to investigate a property of the lower trophic levels in the Lagoon Notoro-ko, we monitored salinity, temperature, dissolved oxygen and nutrient concentrations in the water column vertically during April to December from 2007 to 2009 (non-iced season). Stratification of the water column was found to occur during June to August and oxygen-deficient water mass was generated in bottom water. Concentration of silicate, phosphate and ammonium were higher in the bottom water. The fundamental importance of these nutrients is that the rate at which they are supplied may determine the rate of primary production. Oxygen-deficient water mass is generally recognized to produce negative effects on fisheries, however, the results of this research showed that it may work to supply nutrients to primary production in Lagoon Notoro-ko.