Abstract
Appearances of algae blossom at the sea surface and anoxic water over the sea bed have often been observed in the enclosed coastal area at the head of Osaka Bay. In particular, special attentions have recently been paid to the anoxic water, because it finally relates to lives of fish and shellfish. In this paper, we present the results of our field observation of temperature, salinity, chlorophyll-a, dissolved oxygen, and so on at 15 stations in the Port of Amagasaki-Nishinomiya-Ashiya every week from June to September, 2002. During the period, blue tide, that is, upwelling phenomena of anoxic seabottom water was able to be observed in the enclosed coastal area under the north wind blowing, but the water existed strongly over the seabed after the dramatic change. The effect of rainfall was limited at the sea surface and did not have an impact on anoxic water in the port. In addition, the thickness of the water depended on the depth of thermocline, not the strength of stratification.
