Yang-Ming Lake (YML) in Kinmen was chosen as a experimental site to verify the applicability of using the food-web technology for improving the water quality in the water reservoir. Sampling of aquatic organisms was started from May to November. The results of water quality indicated that it was a hyper-eutrophic, organically polluted environment with phytoplankton dominated by Cylindrospermopsis raciborskii, a cyanobacterium. The capabilities of N-fixation, being able to grow auto- and heterotrophically, and producing toxin were considered to be the main reasons why this species over-dominated other organisms. Low primary productivity was measured in YML. In addition, very low species diversity of phytoplankton gave rise to a very low diversity of zooplankton and fishes. Aquatic animals were sampled at three sites along the YML lakeshore from May to October. A total of 2 shrimp species within 2 orders were recorded, it included Macrobrachium nipponense and Caridina longirostvis. Seasonal fluctuation showed a highest number in summer and decreased obviously after September. A total of 2 benthic organism species representing 2 orders were observed, it included Cipangopaludina chinensis and Pila canaliculata. There were aquatic insects 4 species belonging to 4 orders, it included Aquarius elongates, Nepa chinensis, Chironomidae sp. and Hexatoma sp., etc. A total of 6 fish species within 4 orders were recorded, there were Cyprinus carpio, Pseudorasbora parva, Puntius snyderi, Gambusia affinis, Orechromis sp. and Rhinogobius giurinus. It were found that the populations of Pseudorasbora parva and Rhinogobius giurinus were the dominate species. In order to prevent and improve the eutrophication of Yang-Ming Lake in Kimen, 7,600 freshwater clams (Anodonta woodiana) were caged and cultured at the surface layer of less them 1.5 m depth, followed by a monthly investigation of water quality, clam growth and it survival rate. It was found that survival of freshwater clam decreased with months, 50-60% survival was noted after 5 months culture period. Growth of clam shows no increment or even a slight reduction, it is suggested that monotone of lake ecology, especially the dominance of blue-green algae may contributed to the low survival and decreased growth. Therefore, some suggestions including removal of bottom sludge, improvement of water quality and change of lake ecological as well as more clams needed in lake are mentioned and discussed. Yang-Ming Lake (YML) has low inflow rate and long hydraulic residential time. The results of the sampling and analyses of its water indicate that there is strong horizontal mixing which results in no difference between site A and site B for water quality parameters. However, there is different extent of stratification especially in July and August. The extremely low dissolved oxygen in the bottom water indicates high oxygen demand of sediment. High rate of photosynthesis results in high pH and dissolved oxygen in the surface and evidence of eutrophication. The ratio of the external load and internal load of nutrient is 4.97. External load is the major source of nutrient in the summer, however, internal load is the major source in the winter due to low precipitation and complete mixing in the water body.

Eco-engineering,Food web experiment, Reservoir water quality