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.

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The objective of this thesis is to examine the effects of clay minerals on the growth and nutrient intake of hydroponic tomatoes. Addition of the clay mineral to culture medium had no significant effect on the experimental results. For instance, fresh plant weights at the control plot (No. 1), crystalline clay (illite, kaolinite, vermiculite, and chlorite) plot (No. 2), and non-crystalline clay (allophane) plot (No. 3) were 672 g, 657 g, and 715 g, respectively. In addition, fruit yields at plots No. 1, No. 2, and No. 3 were 1003 g, 1019 g, and 1235 g, respectively. Therefore, an increasing trend was observed in the fruit yield and plant growth in No. 3. For inorganic nutrient absorption, the apparent absorption speed remained high in No. 3 (allophane) compared with those in other plots. Therefore, our results suggest that addition of amorphous clay minerals affects plant growth and nutrient intake.

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