| A re-meandering project was implemented for the stream eco-system restoration of the Shibetsu River, Hokkaido Island, the northern part of Japan. It has been well known that the alteration of planview has an influence on stream structure such as pools and riffles, but there is only a little knowledge about changes in the energy flow of stream ecosystems. The present study evaluated the alteration of primary production rate brought by the re-meandering project comparing a re-meandering section with an upstream straight section. The single station diel O2 curve method and the light and dark bottle method were applied for the measurement of primary production rate, and both methods indicated that primary production rate was higher in the re-meandering section than the straight section. The analysis of factors determining primary production rate showed that the biomass of epilithic algae was lower in the straight section than the re-meandering section. The field observation gave the different view of lateral distribution of bedload transport between two sections: bedload transport in the straight section was considerably uniform across the channel, whereas it was heterogeneous and the transport was limited t o the small area of the re-meandering section. Previous studies show that bedload distribution tends to be skewed in curved channels and the frequent collision of bedload particles with substrate leads to the biomass reduction of epilithic algae. From these findings, we concluded that infrequent dislodgement of epilithic algae induced by the re-meandering treatment with small bedload area resulted to the high biomass and it enhanced the primary production rate of the re-meandering section. |
