We developed a new algal examination system in which chlorophyta Pseudokirchneriella subcapitata can grow well regardless of nutrient conditions. When the cell during the late logarithmic growth or early stationary phase of preculture was added to test water without nutrients and cultured for 4 h, the maximum specific growth rate was obtained. This method was applied for the evaluation of a complex effect between nutrients and pyrogallic acid （PA）, which was well-known as a growth-inhibiting chemical. The result showed that the existing algal examination tests could misestimate the growth-inhibiting effect of PA due to the complex effect. The developed system can be a useful tool to demonstrate a complex effect between a test chemical and a nutrient in a medium, and to evaluate a growth-inhibiting effect of wastewater and ambient water.

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A feasibility study was performed to evaluate collecting pseudofaeces in bivalve farming to improve water quality of a pond located in a city park. The pond is suffering from thick growth of phytoplankton, especially of cyanobacteria that form algal mat, such as Microcystis spp. Bivalve expels non editable suspended solids or surplus diets as pseudofaeces that do not pass through intestinal tract. The possibility of cyanobacteria pelleted as peudofaeces to regrow was elucidated.

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This study aims to clarify the effect of microcystin on the germination, plant growth, absorption and accumulation of three kinds of aquatic plants― Konatsuna, cabbage, and morning glory by soil cultivation. The results indicated that germination and growth of, Konatsuna, cabbage, and morning glory were not inhibited by 1,000μg・l^－1 microcystin－LR added, suggesting there was no effect of germinate by direct sowing. It was also confirmed that microcystin－LR was accumulated in soil cultivation for morning glory. The microcystin－LR was not accumulated in komatsuna and cabbage soil cultivation due to the adsorption and degradation by the soil. When high microcystin－LR concentration was used (1,000μg・l^－1), it was confirmed that microcystin－LR was accumulated in soil cultivation for water morning glory. From the risk assessment by estimation daily intake and tolerable daily intake of komatsuna, cabbage and water morning glory, it was clear that there was no influence on human being for eating crops irrigated the water containing microcystin－LR less than 1,000μg・l^－1.

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Citrobacter freundii IFO 13545 produces a chitosan-like bioflocculant (BF) from acetate. The effects of other organic acids (citrate, fumarate, malate, glyoxylate, succinate, and oxaloacetate) as carbon sources on the growth and flocculation activity (FA) of the cultures were investigated. Citrate, fumarate, malate, succinate, or oxaloacetate supported the growth of IFO 13545 as a sole carbon source, but any FA was not detected during the growth on these organic acids. Glyoxylate did not serve as a carbon source. These organic acids were tested for a possibility as auxiliary carbon sources by adding each organic acid to a basal medium including 10 g l^－1 acetate (AM). However, with the exception of malate, they all negatively affected FA at 1 g l^－1 in AM. As a supply of amino acids, the effect of casamino acids on FA was also investigated. Unexpectedly, casamino acids considerably reduced FA at a concentration of 1 g l^－1 in AM, although it improved the growth greatly. To determine which constituents caused FA reduction, the effects of individual amino acids were evaluated. Valine and tryptophan were found to strongly repress FA, even at low concentrations (≥10 mg l^－1). Furthermore, to select complex organic nutrients suitable for BF production media, the effects exerted by yeast extract, peptone, and tryptone on FA were also investigated. Intriguingly, yeast extract and tryptone negatively affected FA, even at a concentration of 1 g l^－1, although peptone did not have significant effect at the same concentration. These results demonstrate that ubiquitous organic acids, amino acids, and complex organic nutrients can significantly affect the FA of IFO 13545 even at low concentrations.

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Attached algae were collected from the Oppe River at Sakado-shi, Saitama prefecture. The valves of the diatom in this study were examined at 2000x magnification with microphotographs of 373 valves by light microscopy and the nine valves were observed by scanning electron microscopy.Te valves in this study are coincident with Navicula subrostellata Watanabe et al. nomen nudum （Watanabe ed. 2005）. As this taxonomical name is nomem nudum, we propose the new name Navicula watanabei H. Fukush., Kimura &. Ts. Kobay.

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