Speaker: Professor Kwang-Guk An, Department of Biology, Chungnam National University

In this presentation, I introduce the “four major rivers project” in Korea, and show some of the changes in physical, chemical, and biological characteristics that occurred after the constructions of weirs and fishways in the project. I will also discuss the sudden massive blooms of bryozoa (Pectinatella magnifica) that occurred after the weir construction and eco-toxicity tests. Water residence time increased in the rivers after the constructions of the weirs, and areas with stagnant-water (relative to running water) increased. Nutrients of total nitrogen (TN) and total phosphorus (TP) in epilimnetic water decreased after the project, whereas chlorophyll-a (CHL) and CHL:TP ratios increased. Massive algal blooms occurred frequently in the rivers and decreased DO near the weirs, resulting in massive fish kills. In addition, fish passage in the fish way and weirs were monitored by various fish monitoring methodologies (passive integrated transponders (PITs) tags, ultrasonic telemetry, video recording, trap-setting, and eco-sounder monitoring) and evaluated. Finally, I assessed the overall river ecosystem health, based on the multi-metric model of “Index of Biological Integrity” using fish assemblages, both before and after the completion of the project; its appears river health declined after the construction of the project weirs. These are preliminary results based on a very limited dataset and a short post project study period, but will I hope, contribute to the ecological conservation of our national rivers in Korea.