English TOP > Research projects
Faculty of Science
Department of Environmental Science
Laboratory of aquatic ecology
Chiba, 274-8510 Japan
Lake Inba (Chiba, Japan)印旛沼
Chytrids, parasitic fungi of phytoplankton, are found to play an important role in food webs in lakes. We are currently investigating the distributions and the dynamics of chytrids in Japan. Our recent field is Lake Inba,largest lake in Chiba Prefecture. In 2008, Lake Inba was listed as the most eutrophicated lake in Japan (the highest COD).We can see spring blooms of diatom, Aulacoseira, and bloom of cyanobacteria, Microcystis, in summer.On the dominant diatom, Aulacoseira granulata, we have found a chytrid! Chytrid can be clearly identified if we use Calcofluor white, staining chitin.
Daphnia likes chytrid!?
All chytrids have free-swimming stage, zoospores, with which chytrids enlarge their distribution. Zoospores are 2-3µm diameters, and well within the range of food size of Daphnia. We found that Daphnia in fact could eat zoospores. Moreover, zoospores are found to be good foods for Daphnia. They contain large amount of choresterols, which are essential nutritions for zooplankton. Although Daphnia cannot eat large diatoms, such as Asterionella, they can eat zoospores which attack large diatoms. Thus, Daphnia can grow with zoospores even in the presence of inedible diatoms.
When Daphnia eat chytrids, what will be changed? In general, large diatoms sink to the lake bottom without being grazed by zooplankton. If large diatoms are infected by chytrid, however, materials within diatoms are consumed by chytrids before sinking. Then, chytrids are partly eaten by zooplankton. Thus, large diatoms are indirectly consumed by zooplankton via chytrid zoospores. This new pathway is now named as Mycoloop, after Mycology and my name (Maiko)!