Coastal Waters Study in Hokkaido – and especially, the Sea of Okhotsk –
Ryuji Fukuya1), Katsunori Anezaki1),Sei-ichi Saitoh2) ,Hideki Minami3)
1)Hokkaido Institute of Environmental Sciences, 2)Faculty of fisheries sciences, Hokkaido University.
3)Department of Marine Biology and Sciences,
The Sea of Okhotsk and its catchment are among the most vulnerable areas to human activities. A great deal of pollutants such as chemical compounds, acid materials etc. involved in aerosol is accumulated in this famous graveyard of low pressure system. Furthermore, these pollutants discharge in Amur River after a previous accumulation in the catchment area. Recently, the Tsushima warm current has been melting the sea ice, and frequently intruding into the Sea of Okhotsk during winter season. These phenomena are getting more and more remarkable due to global warming. We are actually investigating the water quality and substrates around Hokkaido coastal sea areas, using the satellite-derived imageries and the analyzed in situ data. From these investigations, the new findings are as follows:
- The phytoplankton blooming triggered by fresh water from the Ishikari River, and its movement into the Sea of Okhotsk were observed by satellite-derived imageries using SeaWiFs of the year 1999. Transportation of pollutants by the northern movement of the ocean polar front is expected to increase into the Sea of Okhotsk.
- The results of the chemical compounds such as POP’s, analyzed in the substrate of the Sea of Okhotsk, indicated the possibility of POP’s accumulation in the Sea of Okhotsk. The high level of POP’s in the Sea mammals’ fat of this sea area was reported by the Institute of Cetacean Research in 1996.
- The frequency of precipitation of more than 100mm has been high during this decade. This was followed by the increase of the loading of pollutants, such as organic substances and nutrients, discharged from inland to the Okhotsk coastal sea areas. The stratification in lagoons in the nearby Sea of Okhotsk is lengthened by the global warming. This heavily affects the aquiculture industry through the evolution of nutrients and sulfides at the lake bed.
Keywords: coastal waters; Okhotsk; chemical compound; remote sensing