抄録
The biomass and density of the kelp Saccharina japonica var. religiosa fluctuates over the years on
the southwest coast of Hokkaido. The purpose of this study is to identify the period which water
temperature affected on biomass and density of the kelp. Relationships between the biomass and density
of the kelp and ten-day mean water temperature （TDMWT） was examined these based on a 2001-2014
monitoring study data-set on biomass and density of algae and sea urchin in June at Oshoro inlet,
Hokkaido. Correlation coefficients were calculated to compare between TDMWT from the previous
November to next May and the kelp biomass and density in June. There were significant negative
correlations between TDMWT in February and the biomass, and TDMWT from January to early March
and the density of the kelp in June at the depth of 0.4m, respectively. We consider that low water
temperature in the winter season led to an increase in the density and accelerate the growth of the kelp
directly and indirectly via oceanographic factors associated with the low water temperature in this
period, e.g. nutrient concentration. Furthermore, low water temperature in the spring season influences
the biomass and density of the kelp via supplying nutrient by snowmelt.
