We developed a method for the mass cultivation of the cyanobacterium Anabaena macrospora （syn. Dolichospermum hangangense） and for the mass production and collection of dormant cells, successfully germinating these dormant cells after a specified dormancy period. In this study, by using this method to evaluate the germination of dormant cells, we assessed how water temperature and oxygen conditions during dormancy affect the survival and germination of these cells.

  The results indicated that dormant cells maintained a high survival rate at low temperatures, whereas their survival rate diminished at high temperatures. Furthermore, dormant cells demonstrated a high survival rate under anaerobic conditions but perished in aerobic conditions. It was also discovered that dormant cells can germinate after more than three months of dormancy. They typically germinate synchronously when environmental temperatures shift from low to high, but they rarely germinate when temperatures change from high to low. Dormant cells that did not germinate at high temperatures during dormancy may germinate when exposed to low temperatures. This indicates that dormant cells can enter a state of secondary dormancy.

 To maintain the water quality of Lake Inawashiro, which has become neutral pH and is suspected to be water pollution, a demonstration test facility for water purification was constructed near Akai River flowing into Lake Inawashiro by the Fukushima Prefectural Centre for Environmental Creation. The facility is composed of a pretreatment tank （“Pretreatment”）, two surface flow constructed wetlands （“1st CW”）, and two vertical flow constructed wetlands （“2nd CW”）. The purpose of the demonstration test is to reduce the pollutants introduced to Lake Inawashiro from paddy fields. This study reports the design of the demonstration test facility and the removal effects during an irrigation period. The suspended solids （SS） and particulate phosphorus （PP） concentration in raw water （Akai River） dramatically increased because of soil puddling. During periods when the paddy field was not under cultivation and flooding （i.e. the ordinary period）, the following results were obtained. When removal efficiency （%） was selected as the performance indicator, it was productive for the best water purification to put into full-scale operation after an investigation of the relationship between a hydraulic load and a removal efficiency. When removal rate （g/m²/d） was selected as the performance indicator, it was productive for the best water purification to operate the facility at a higher loading rate. During soil puddling, the facility exhibited an effective inflow removal effect because the removal rate and loading rate of SS, total organic carbon （TOC）, total phosphorus （TP）, PP, total nitrogen （TN）, and particulate nitrogen （PN） were positively correlated （p ＜ 0.01） and the inclination of regression lines in all water quality was larger than the inclination during the ordinary period. Turbidity in the 1st CW treated water varied with changes in the raw water, while turbidity in 2nd CW treated water was low and only changed slightly. Therefore, the vertical flow constructed wetland was necessary to effectively remove high concentrations of particulate pollutants during soil puddling.

 Mallomonas and Synura belonging to scale-bearing chrysophytes are known for causing taste and odour problems in water supplies. Therefore, scale-bearing chrysophytes from the south basin of Lake Biwa and Seta River that are the source of water supplies in the Kansai area were investigated between October 2022 and November 2024. A total 31 species and 1 variety; 20 species and 1 variety of Mallomonas, 2 species of Synura, 6 species of Spiniferomonas, 1 species of Chrysosphaerella, and 2 species of Paraphysomonas were found. Among them, Mallomonas hamata and M. multiunca were new to Japan, and M. acaroides var. obtusa, M. areolata, M. retifera and Spiniferomonas alata were first reported from Lake Biwa and Seta River. Mallomonas caudata, M. elongata, M. portae-ferreae, M. tonsurata, Spiniferomonas bourrellyi, S. trioralis and Paraphysomonas vestita were found in many samples of four seasons.