We determined tributyltin (TBT) concentrations in seawater and bottom sediment samples collected from coastal areas around northern Kyushu in 1998. The concentrations ranged from 5 to 94 ng/L in seawater and from 7 to 1,100 ng/g dry mud in sediment. High concentrations in water and sediment were detected in Hakata Bay (water: 13-94 ng/L , sediment: 18-1,100 ng/g dry mud). In the Ariake Sea, the TBT concentrations in water (5-91 ng/L) were as high as those in Hakata Bay, whereas the TBT concentrations in sediment (16-77 ng/g dry mud) were lower than those in Hakata Bay. The higher concentrations in water collected from the Ariake Sea may be attributable to the suspension of TBT-containing sediment due to tidal turbulence which is peculiar to the Ariake Sea.

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This study aimed at characterization of a simple aquatic microcosm consisting of algae Euglena gracilis as a producer, ciliate protozoa Tetrahymena thermophila as a consumer and bacteria Escherichia coli as a decomposer. The authors investigated changes in the cell densities, photosynthesis and respiration rates in the microcosm and its pure-culture systems when exposed or unexposed to copper. The following characteristics were deduced from the results. (1) The microcosm mimicked essential processes in natural aquatic microbial communities. That is, development of the microcosm could be regarded as a combination model of heterotrophic and autotrophic development in natural aquatic microbial communities. After such development, the microcosm reached a mature stage, in which the photosynthesis rate was balanced with the respiration rate. (2) The microcosm could evaluate not only direct effects of toxic agents but also community-level effects due to interspecies interactions or interactions between organisms and toxic agents. (3) The microcosm would have almost the same sensitivity to toxic agents as some other microcosms consisting of more diverse microbes. These three characteristics indicated that the microcosm studied was useful for community-level ecotoxicity screening for aquatic microbial communities.

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Cytotoxicity of 19 pesticides used in golf links to two suspension-cultured cell lines from fish (CHSE-sp cell line and FHM-sp cell line) was determined by neutral red assay. The details of the pesticides were 7 insecticides, 7 fungicides and 5 herbicides. Oxine-copper, Chlorothalonil, Thiuram and Captan (they are fungicides), and Chlorpyrifos (insecticide) were highly toxic to both cell lines. It is well known that these pesticides are also highly toxic to carp and water flea. There was good correlation (r > 0.8) between 24-h NR₅₀ to both cell lines and 96-h LC₅₀ to rainbow trout fry and 48-h LC₅₀ to carp of the pesticides used in this study. There was also good correlation (r=0.981) between 24-h NR₅₀ to the CHSE-sp cell line and the FHM-sp cell line. The ratios of NR₅₀ to LC₅₀ (NR₅₀/LC₅₀) of pesticides tested were more than 1. Sensitivity of in vitro test using suspension-cultured cell lines from fish to pesticides was lower than that of in vivo test using whole fish body. However, the suspension-cultured cells can be inoculated directly to the microplate well and the correlation between in vitro test using these suspension-cultured cells and in vivo test using whole fish body was relatively high. Therefore, the suspension-cultured cell lines derived from fish might be useful screening tools prior to in vivo testing of pesticides used in golf links.

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Vitellogenin (Vtg) is a female specific plasma protein and the major precursor of egg yolk protein in oviparous animals including fish and serves as a useful indicator of exposure of male or juvenile fish to estrogenic compounds. To assess possible estrogenic activity of effluent from sewage treatment works in Japan, we examined plasma Vtg concentration of juvenile Koi carp that were exposed in situ to the effluent by maintaining the fish in a cage deployed at a point downstream from the outfall of effluent. In the first trial with the juvenile fish (232 ± 99 g in body weight, n = 40) for 10 days, the exposure significantly (p < 0.01) increased the plasma Vtg concentration in the juvenile male group and the juvenile mixed-sex group. In the second trial with more and younger Koi carp (65 ± 23 g, n = 120) for 15 days, the effect of the exposure was more evident than in the first trial, with the statistical significance (p < 0.01) for each sex group. These results suggest that the effluent from a sewage treatment works had a weak but enough estrogenic activity to increase plasma Vtg levels of juvenile Koi carp. Chemical analyses for several compounds with estrogenic activity in the water samples at the exposure point suggest that natural estrogens, such as estradiol-17β and estrone, were possible candidate compounds responsible for the observed increase in the plasma Vtg levels.

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A convenient, simple and rapid cytotoxicity test using cultured cell lines from fish was carried out to know the toxicity of commercial products to fish. Three extinguishing agents (Phos-chek, Jet form III and Miya form) were selected as the commercial products. The FHM-sp cell line, which is the cell line of improved type of the FHM cell line derived from peduncle of fathead minnow, was used as the suspension-cultured cell line from fish. Cytotoxicity of three extinguishing agents to the FHM-sp cell line was determined by neutral red uptake inhibition test. The cytotoxicity of three extinguishing agents was compared to the in vivo toxicity of them obtained by three ecotoxicological tests (algae growth inhibition test, Daphnia magna acute immobilization test and medaka acute toxicity test). The rank order of the in vivo toxicity of three extinguishing agents was the same in three ecotoxicological tests and Phos-chek> Jet form III> Miya form. There is no regulation standard on toxicity of extinguishing agents to aquatic organisms in Japan. Following the regulation standard of National Fire Protection Association (NFPA) in U.S.A., the effect of extinguishing agents tested on aquatic organisms like fish was little in regular use for extinguishing. The rank order of cytotoxicity of them to the FHM-sp cells was Phos-chek> Miya form > Jet form III. However, the difference of cytotoxicity value between Miya form and Jet form III was a little. The value of 24h NR₅₀ to FHM-sp cells was near to that of 96h LC₅₀ to medaka. Therefore the sensitivity of the in vitro toxicity test using the FHM-sp cells to three extinguishing agents was similar to that of the in vivo toxicity test using medaka. The toxicity values of three ecotoxicological tests (72hEC₅₀, 48hEC₅₀, 96hLC₅₀) and the cytotoxicity test (24hNR₅₀) to three extinguishing agents were in the same range and 10-50 mg/L. This shows that the in vitro toxicity test using the FHM-sp cells is useful to estimate the range of test concentration for in vivo toxicity tests.

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The absorption and immigration of Cr and Cu in the mulberry seedlings were investigated by using the hydroponic solution that Cu coexisted with Cr. The two-factor design experiments were carried out in the total 25 addition-areas, namely, 5 addition-areas with 5-level concentrations of Cr (0, 0.5, 2.0, 4.0 and 8.0 mgl^-1 ) based on the normal hydropoic solution, and corresponding to each area of Cr addition, 5-level concentrations of Cu (0, 1.0, 3.0, 6.0, 12.0 mgl^-1 ) were designed. It was observed that, at low concentration of Cu, the concentration and amounts of Cr and Cu in the mulberry seedlings were low with the same level, probably due to the competitive effect. Such absorption of Cr and Cu indicated that their absorption was attributed to antagonistic phenomenon. However, when both Cr and Cu were of the high concentrations, the toxicity of Cr and Cu were added, and the concentrations of Cr and Cu in the roots were much higher than those of solely adding Cu due to the deterioration of the exclusive function of roots.

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