In the coldest and driest season of the year (i.e., February 3 and 4, 1968) measurements were taken on water temperature, chlorinity, pH and phosphate-P, ammonia-N, nitrite-N and nitrate-N contents of sea water off the estuary of the Ashida River, occupying 14 stations both at a high and a low water.
The water temperature was within a range of 6-8°, its vertical variation being very slight reflecting the vertical circulation of water due to convective cooling. Chlorinity also demonstrated a slight vertical variation due to the same cause in all places except in the close vicinity of the river mouth and in the waste water discharged from a chemical plant. Normal pH values were encountered everywhere except in the vicinity of the chemical plant where values as low as 2.4～8.0pH were measured.
Nutrient contents of sea water were low in the offing, and somewhat higher near the estuary of the Ashida River, and abnormally high in the water samples affected by the waste water from the chemical plant.
Possible effects of such distribution patterns of sea water properties on the cultured laver were discussed.