On the Distribution of the Diatoms off South-Bast Coast of Hokkaido with the Consideration of Hydrographic Conditions

Abstract

The present report deals with the distribution of diatoms off south-east coast of Hokkaido, during Oct., 26 to Nov., 25 1947. The stations where the collections and observations were made can be seen in Fig. 1. The species of diatoms studied were listed in the accompaning table. From the data obtained by the present observation the water has been led to conclude that the area studied should be divided into following five region.
“Region A”……where the Genus Chaetoceros predominates.
“Region B”……where the following species are found in abundance,
Skeletonema costum
Asterionella japonica
Chaetoceros socialis
Nitzchia seriata
“Region C”……where the monotonic vegetation of C. tripos is found.
“Region D”……where the species Rhizoaolenia slats flourisches monotonously.
“Region E”……where the Genus Coscipodiscus vegetates.
By considering the above region in connection to the hydrographic conditions of corresponding areas it can be pointed out that the “Region A” is thearea where the warm current named “Tsushima-kairyu” prevails. Incontrast to this the “Retion C” and “Region D” is the areas where the influence of cold current i.e. “Oya-shio” is prominent. While the “Region B” is a neritic region, and the “Region E” is the area where the upwell of cold bottom water is found.