STUDIES ON THE UNDER-ICE PLANKTON OF THE OVERWINTERING FISHPONDS

This paper embodies the results of investigations on the under-ice plankton in over-wintering fish ponds during 1978—1981. They may be summarized as follows:1. There are not so many species of phytoplankton and zooplankton under winter ice, but their standing crops can be not lower than those in comparable ponds at growing seasons.2. The average biomass of phytoplankton was 38.8 mg/l, in which the dominant forms were: Glenodinium, Cryptomonas, Chroomonas, Chlamydomonas, Ochromonas, Trachelomonas, Cyclotella, Chlorella and Scenedesmus.3. The biomass of zooplankton averaged 6.21 mg/l, and was composed mainly of rotifers and cyclopoidea.4. The standing crops of phytoplankton showed a vertical variation, which in general was higher at the surface layer. Certain flagellates such as Glenodinium exhibit diurnal vertical movements in under-ice waters.5. There is a negative correlation (r=-0.435,n=153) between the phytoplankton biomass (x) and transparency (Y). The equation is:Y=83.91-0.72xIn this paper the correlations of the under-ice plankton with the ecological factors are also discussed.