Abstract
Eutrophic coastal bottom environments are often under serious oxygen depletion in a stratified summer season, and the heterotrophic activities in the environment decreased significantly. For improving such anoxic conditions and stimulating self-purification ability, we supplied light into the bottom water through an optical fiber and stimulated the photosynthetic activities of phytoplankton. Results indicate that 15 uE m-2 s-1 of irradiation always resulted in net production of dissolved oxygen (DO). In winter, on the other hand, when DO was sufficient but low temperature was the limiting factor for the heterotorphic activities, addition of psychrophilic bacteria stimulated the microbial activities in the bottom environments. These results indicate that the combination using optical fiber and psychrophilic bacteria is promising strategies for the bioremediation of eutrophic bottom environments.
