Abstract
Relationships between land use and the carbon and nitrogen stable isotope ratio of riparian plants, aquatic algae and masu salmon juveniles of seven rivers in the coastal area of Ishikari Bay Hokkaido, Japan were examined. Principal component analysis was conducted to characterize the land use of these rivers. The correlation between the principal component scores and the stable isotope ratio of riparian plants, aquatic algae and masu salmon juveniles in these rivers was analyzed. The first principal component (PC1) accounted for 47 ∼ 57% of the variance of land use variables. Component loadings of PC1 were positive high in the land use of agricultural land or artificial forest, and were negative high in the land use of natural forest and natural grassland. A positive correlation was observed between the principal component scores of PC1 and the nitrogen isotope ratio of aquatic algae and masu salmon juveniles. These results suggest that the nitrogen stable isotope ratios of aquatic algae and masu salmon juveniles are influenced by land use. These stable isotope ratios provide a useful index of the human impact on stream ecosystems.
