Abstract
When the night soil is used as the manure for planktons in seawater, decomposition ratio of night soil has greatly effect upon multiplication ratio of planktons. Two of seawater for culture medium, one high nutritive value, the other low nutritive value, were adopted in this study. Several night soils with different composition ratio were added into the seawater, and numbers of planktons (diatom, other unicellular algaes, dinocontae, and other zooplankton) were measured.
The night soil with the high decomposition ratio was effective on the multiplication of various planktons, especially for diatom or dinocontae. Most of diatoms appeared in the first half of the cultivation period, and most of dinocontaes appeared in the latter half of that period. When the night soil with high decomposition ratio was added into the seawater, phytoplankton early appeared in comparison with the addition of the night soil of low decomposition ratio. Accordingly, it can be said phytoplankton take the decomposed products of night soil as a bait. The multiplication ratio of plankton was changed by difference of the seawater. The fact suggested that effect of decomposition ratio on multiplication ratio depended on the concentration of nutritive value in seawater.
