Short-term variation in abundance of four species (Copepoda, Calanoida) in a eutrophic bay.

The short-term variation in the abundance of copepods in the eutrophic Gamak Bay of South Korea was investigated with weekly measurements from October 2007 to September 2008. During this period, four species (, . , . , and . ) were recorded as showing seasonally different peak abundance. The abundance of . and . was high in autumn, whereas that of . was high from winter to spring. In summer, , . and . coexisted at peak abundance significantly related to water temperature and salinity. Results from the response curves of the four species to water temperature and salinity suggest that . and . increased in abundance at water temperatures >18 °C, whereas . increased in abundance at water temperatures >27 °C. The occurrence of . , . , and . decreased with increasing salinity, but chlorophyll- concentration showed no effect on occurrence. Despite these findings, the coexistence of the three ecologically similar species may be due to prey abundance in summer and autumn (chlorophyll- concentration >10 µg L). Notably, the wide range of the response curve of indicates its occurrence at higher salinity levels than other species.