The present study attempts to determine the effects and limits of current water-quality preservation measures. The target region was the watershed of Lake Biwa. We also suggest future directions for watershed management.
The carrying capacity of COD, TN, TP of Lake Biwa estimated by multiplying the allowable concentration of pollutant loads by the volume of inflow. The allowable TN, TP concentration of inflow was determined using Vollenweider's model. Separately, the allowable COD concentration of inflow was determined by subtracting “produced COD concentration in the lake” from environment standard concentration.
The carrying capacity of Lake Biwa was estimated to be 1.4, 2.7, and 0.59kton·y^-1 of COD, TN, and TP, respectively.
Under a scenario of an increasing number of pollution abatement measures, even under the strictest of scenarios, COD and TN loads would still surpass the carrying capacity by 4.6 and 1.8 times, respectively.
The results of the present study demonstrate that there is a limit to the degree to which the water quality at Lake Biwa can be controlled via the implementation of tichnological measures. Therefore, the concept of growth management, which rationalizes social economic activity itself within the watershed, is indispensable for future watershed management.

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Water pollutants from domestic wastewater (major ingredients of detergent or soap, bactericides used for medicated soap, fablic softener, hair rinse and so on) were tested with bread yeast (AOY-I) for detecting their interactive toxicity whose endpoint was growth inhibition. Lethal effects were observed on systems exposed to cationic surfactant or synthetic surfactant-organochlorine bactericide mixed samples. Strong inhibition were observed on systems LAS and fluorescent whitener (DAS-I). No inhibition were observed on systems exposed to AE, soap and mixed samples containing soap.
Synergistic effects were clearly shown on systems exposed to organochlorine bactericides with synthetic surfactants especially in cases of including AE. These results suggested that synthetic surfactants might cause damage to cell membrane consisted of phospholipids, then absorbed other toxic chemicals into cells.

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The saturated magnetization σ(emu·g^-1) was measured for the ferrite sludge formed by two-step treatment with pH adjustment of wastewater containing nickel sulfate. Simultaneously, the concentration of nickel and iron ions in the treated water was measured. The effect of pH adjustment on the above parameters was quantitatively discussed by comparing the two different treatments: conventional and two-step treatments.
The σ of ferrite sludge formed by the two-step treatment with pH adjustment was slightly larger than that by conventional and two-step treatments. XPS measurement of the sludge formed by conventional and two-step treatment with pH adjustment indicated the existence of Ni(OH)₂ on the surface of ferrite particles. The measurement after Xe⁺ sputtering showed that the Ni(OH)₂ is present not only on the surface but also in the bulk of the particles formed by conventional treatment. In leached test, the concentration of nickel ion in the elute was lower in order of conventional, two-step and two-step treatment with pH adjustment in relation to Ni(OH)₂ on the surface of ferrite particles.
The two-step treatment with pH adjustment stabilizes the sludge and is favorable for steady operation of the ferrite process, industrial utilization of the sludge and good quality of the treated water.

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Seasonal change of microbial community including bacteria and algae in Tsukui Lake, an eutrophic reservoir in Kanagawa prefecture, was investigated by denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplified fragments of 16S rDNA from May to October in 2000. A sudden algal bloom of cyanobacteria (Microcystis sp. and Anabaena sp.) after a heavy storm in July was observed both from a traditional algal cell counting and from a DGGE banding pattern analysis. In order to express graphically the seasonal change of the community based on the dissimilarity index, multi-dimensional scaling (MDS) was applied. The MDS map revealed a cyclic change of the community and a distinctive divergence from the path during the agal bloom. Since the divergence disappeared in an analysis with the DGGE image excluding the bands of cyanobacteria, the major part of the community appeared in the DGGE image might be independent of the sudden algal bloom. Dissimilarity of microbial communities was much lower among three different sampling sites than among the sampling months.

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A number of bioassays for screening the compounds for estrogenic activity have been proposed so far, however, a yeast two-hybrid system appears more simple and inexpensive assay with high repeatability. The biggest problem of this bioassay is that it cannot measure estrogenic activity in some of the environmental samples. At is was assumed that the co-existing compounds were responsible for these false negatives, two methods were tested:
1. Separation of such co-existing chemical interferences by use of liquid chromatographic method.
2. Masking the retarding effect of such co-existing chemicals interferences by the addition of S9mix.
The results indicated that both methods were effective to identify the estrogenic activity, however, the addition of S9mix was much more simple to conduct and more effective to determine the estrogenic activity in environmental samples.

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A red tide occurred over a small portion of they bay in the 1980s. And a red tide has been transported up the South, West and East seas since the middle of the 1990s. The most common cause of a red tide was flagellate algae since the 1990s. In 1995, accounted for 95% of the total occurrence of the red tide. The harmful red tide was caused by the Cochlodinium that affected fishery operations in 1993 and 1994. Furthermore, it spread to the southern part of the East sea. In late August, 1995, a Cochlodinium red tide occurred frequently in outside of the Narodo coast, and then moved to the western part of the South sea. It lasted a month and then went away at the beginning of October. In August, 1998, It first appeared off the Narodo coast, and then spread repeatedly to the West and East coasts until the 15 of September. By carefully studying water quality, three characteristics of a Cochodinium red tide were identified about a month before the appearance of the red tide, there by effectively preventing a loss to the fishing industry. As a result, the water temperature was high (about 24°C) at the beginning. The concentrations of dissolved nitrate and phosphate were low, especially in the Narodo. However, conditions were favourable for the multiplication of Cochlodinium polykrikoides. With regards to phytoplankton, the amount of flagellate algae went up rapidly in the middle of August. By the latter half of the month, it accounted for 98% of the plant life. With the increase of nitrate and phosphate, the tablated water temperature reached 24-26°C. Cochlodinium red tide occurred in the Narodo coast several days later.

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