Seasonal and diel abundance and feeding patterns of Chaoborus flavicans in Sang-Chun reservoir

To document the basic ecological aspects of Chaoborus species, which has never been reported in Korea, we attempted to identify the species, to monitor seasonal and vertical dynamics, and to elucidate trophic relations of the species in Sang-Chun reservoir. Using morphological characteristics, we identified the collected samples as C. flavicans. Also, we compared the distribution of C. flavicans, Daphnia rosea and chlorophyll a to observed seasonal dynamics. The increase of C. flavicans was observed 1-2 weeks after the increase of D. rosea. Survey of diel vertical migration patterns in the summer season showed that C. flavicans were in hypolimnion at daytime, but moved to the epilimnion at night. Finally, to determine trophic relationships in Sang-Chun reservoir, additional studies on the food web were undertaken by stable isotope analysis. Chaoborus flavicans Ⅰ-Ⅱ instars appear to be filter feeders based on carbon isotope values. Trophic levels of C. flavicans Ⅲ-Ⅳ instars were shown to be higher than other zooplankton based on nitrogen isotope values.