We investigated the growth and chlorophyll-related parameters of the marine diatom Skeletonema marinoi-dohrnii complex （NIES-324） exposed to tributyltin （TBT） or photosystem （PS） II inhibitor Irgarol as a reference chemical for elucidating the effect of TBT on photosynthetic activity. Fifty percent effective concentrations for growth （EC₅₀） were 2.14 μg/L in TBT and 1.14 μg/L in Irgarol. Chlorophyll a content per one cell （pg/cell） was significantly decreased at the highest Irgarol concentration （1.0 μg/L） but chlorophyll c content was not affected. Following TBT treatment, however, both chlorophyll a and c content per cell increased significantly at the highest concentration （2.0 μg/L）. The ratio of chlorophyll a and c content （chl. a/c ratio） decreased significantly and the minimum level of chlorophyll fluorescence （F_o） per μg/mL of chlorophyll a （F_o/chl. a） increased significantly in all Irgarol treatment groups, but TBT had no effect on either parameter. The present results suggest that TBT has no direct effect on electron flow in the photosystem and that the chl. a/c ratio and F_o/chl. a are sensitive bio-markers for detecting the effect of the PSII inhibitor in diatoms.

View full abstract

To compare the distributions of polycyclic aromatic hydrocarbons （PAHs） and alkylated PAHs （alkPAHs） in sessile marine organisms, bivalves were collected from 20 sites along the coastal areas of Osaka Bay in Japan. Both PAHs and alkPAHs in bivalve tissues were determined by GC/MS. Total PAHs （ΣPAHs） were 87.3-361, 212-214 and 70.9-351 ng/g dry weight （dw） in blue mussels, green mussels and oysters, respectively. Meanwhile, total alkPAHs（ ΣalkPAHs） were 466-3293, 950-1788 and 286-2787 ng/g dw in blue mussels, green mussels and oysters, respectively. When compared to their reported concentrations in sediments, ΣPAH were much lower while ΣalkPAH were higher in bivalves. Moreover, ΣalkPAHs in bivalves of each samling site were 1.8-9.8 times higher than ΣPAHs although ΣalkPAHs in sediment of each sampling site were 1.2-4.5 times lower than ΣPAHs. On the other hand, of the PAHs, naphthalene showed the highest concentration in bivalves for most of the sampling sites. Fortunately, benzo（a）pyrene and PAH4 concentrations in bivalves from Osaka Bay were within the EU criteria. For individual alkPAHs in bivalves, the naphthalene, dibenzothiophene, and phenanthrene/anthracene groups were accumulated at relatively high concentrations. These results suggest that the low molecular weight alkPAHs have higher tendency to pollute water columns.

View full abstract

In the present study, gentamicin, which is well known to induce the nephrotoxicities in organisms, were directly injected into the abdominal cavity of carp with nominal concentrations of 0.02 mg/g（ Low group）, 0.063 mg/g（ Middle group） and 0.2 mg/g（High group） and the variations of metabolite profiles in plasma and the relationship between their variations and symptoms on carp were examined, when the nephrotoxicities were caused. In High group, carps seriously affected to exposure and the mortalities of three individuals out of all of five were observed. Meanwhile, although carps in Low and Middle groups were not dead, they were observed decline in urine output, presence with anemia, abdominal selling with ascites, and hematopoietic tissue. In their metabolite profiles, taurine and inositol related to osmoregulation were significantly increased in comparison with control, depending on exposed concentrations of gentamicin from 0.02 to 0.063 mg/g. Ornithine, creatinine, and urine provided the indications of glomeruli condition were also increased in the same range of exposed concentrations. Those increases could be clearly reflected to the symptoms in kidney damages. On the other hand, metabolites for energy generation tended to decrease, because whole bodies of carp were seriously affected to gentamicin exposures and required more energy than usual.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

Humic acid is one of the main components of organic matters in the water environment. In this study, some effects of temperature on the copper adsorption to the humic acid extracted from cray soil (PFAHA) was examined. Complex formation constant (KCu²⁺) of the phenolic sites in the humic acid decreased as the temperature increased. In contrast, KCuOH⁺ increased as the temperature increased. That the ratio of CuOH⁺ to Cu²⁺ in the solution increased as the temperature increased. Adsorption enthalpy of phenolic sites were larger than those of carboxylic sites because it is estimated that change of adsorption species (CuOH⁺) appeared at the higher pH. A linear relationship was found between the complex formation constants and the temperature according to the van't Hoff equation.

View full abstract

The aquatic toxicity of heavy metals is affected by water chemistry such as hardness, pH, and dissolved organic carbon. Biotic ligand models（BLMs）for predicting heavy metal toxicity in consideration of water chemistry have been developed and used for risk assessment. Most of the currently used BLMs were developed in the United States and European Union countries, and thus the target biological species of the models tend to be the species living in those countries. In this study, we investigated the toxicity of copper on medaka（Oryzias latipes）in water having lower hardness and also investigated that how the toxicity varies as a function of Ca and Mg concentrations. By using the toxicity data, we developed a BLM for the fish. We conducted a series of tests of Cu toxicity to juvenile medaka in water with relatively low hardness, ranging from 18.1 to 22.4 mg/L CaCO₃, which is typical of Japanese surface water, and Ca and Mg concentrations（and hence water hardness）are raised separately. We found that Cu toxicity decreased with increasing Ca concentration, whereas increasing the Mg concentration resulted in only a slight decrease in Cu toxicity. A BLM was then developed using these ecotoxicity data. The observed and BLM-predicted 10%, 50%, and 90% lethal concentrations were mostly within a factor of 2 of each other, and hence we concluded that predictability of our BLM is reasonably good.

View full abstract

Estuarine and coastal species are frequently exposed to chemical pollutants including agrochemicals introduced into the environment. Rapid and simple screening method is required for a first step of detecting effects of chemicals, or assessing estuarine water and wastewater from industry or disposal site. Tests using saltwater plankton Dunaliella sp. were conducted and the growth inhibition characteristic by chemicals was studied for developing a standard method, as little information was available for the species. The alga was incubated at 21 ± 0.5°C using 50 mL Erlenmeyer flask for the test vessel with air-permeable stoppers and without shaking. Biomass was determined by cell counting with an electronic particle counter. An exponential growth of the alga was observed over 72 h for control, and reproducible results were obtained. The alga was treated with each of 24 herbicides and 15 widely used chemicals for 72 h for analyzing characteristics of this species. Growth rates were calculated, and a 50 ‰ inhibition of growth rate (ErC50) is determined for these chemicals. Some agrochemicals were highly toxic for this species. Toxicity of chlorophenols and chloroanilines examined was correlated with the lipophilicity of the compound (log Pow of the neutral compound). The susceptibility of the alga was also compared with a most popularly used alga Pseudokirchneriella subcapitata (green alga) using 72-h ErC₅₀. The alga was more sensitive to some chemicals than P. subcapitata and not to other chemicals. Only differences within one order of magnitude in sensitivity were observed for 25 in 36 chemicals. In this test using the alga, the 72-h ErC₅₀ values of the almost chemicals tested were nearly equal to the 48-h or 24-h ErC₅₀ values. The observations suggest that the proposed method can detect algal growth inhibition concentration in a shorter time of 24 h than the 72 h conventional test time and be potentially applicable to assess estuarine or coastal water and industrial effluents.

View full abstract