Kahoku-gata is located at the north part of Kanazawa plain and straddles between Kanazawa city and Uchinada town, Ishikawa prefecture, Japan. In the present study, toxicities of sediments collected from 29 sites in Kahoku-gata and the surrounding water area were evaluated using Japanese medaka embryos. Those sediments with slight pore water were placed in grass petri dishes without overlying water. Some effects were observed in embryos and hatched larvae exposed to sediments collected in three sites in the eastern waterway (Tobu shousuiro), one site in Kahoku-gata, and several sites in Ohno river and the estuary, respectively. However, from the evaluations, sediment toxicities were not relatively serious in Kahoku-gata and the surrounding area, although we could show slightly high risks to aquatic organisms. The remarkable relevance between their effects and residues of pollutants as polycyclic aromatic hydrocarbons, pesticides, and heavy metals couldn’t be found in the evaluations, and the additional explores to find the harmful pollutants will be required.

The Whole Effluent Toxicity (WET) test using freshwater organisms has already been validated for freshwater effluent management. Since the effluent is discharged directly into the coastal areas in Japan, there is an urgent need to establish a WET protocol for marine organisms. The availability of test organisms is important for the WET test, but unlike freshwater organisms, breeding and propagation of marine organisms is often difficult. Although the marine crustacean Tigriopus japonicus is easy to keep and breed, it has been considered to have low sensitivity to chemicals. In this study, we developed a test method to improve the sensitivity of this species. The effect of chemical substances was evaluated by the rate of metamorphosis of nauplii (within 24 h after hatching) into copepodite larvae. Additionally, we compared the EC₅₀ values in this study with those from the U.S. Environmental Protection Agency’s (USEPA) database (ecotoxicity data). The mean EC₅₀ was 2.2 (Range: 0.8–4.7) mg/L for hexavalent chromium (measured concentration) and 0.5 (Range: 0.3–0.8) mg/L for 3,5-dichlorophenol (measured concentration). These values were smaller than 93% in hexavalent chromium and 78% in 3,5-dichlorophenol of the ecotoxicity data for marine crustaceans, indicating that the sensitivity of T. japonicus was high. To clarify the usefulness of this test method, it will be necessary to apply the developed test method to other chemicals and effluent.

To develop ecotoxicity test methods for the ecological impact assessment of cellulose nanofibers (CNFs) in aquatic environments, we summarized the methods and results of ecotoxicity tests used in published articles. We also discussed the points to be considered while conducting ecotoxicity tests for CNFs using aquatic organisms based on the Organisation for Economic Co-operation and Development (OECD) guidance document No. 317 for ecotoxicity testing of nanomaterials. In some published articles, no ecological effects of CNFs on aquatic organisms were observed, even when they were exposed to high concentrations of CNFs. In these studies, test organisms may not have been exposed to nominal concentrations of CNFs because of CNF agglomeration and settling caused due to the low dispersion stability of CNFs resulting from the water quality of the test medium. According to the OECD guidance document, attention must be paid toward dispersibility and dispersion stability, effects of feeding, and factors related to adverse effects, analysis, and measurement of CNFs. No literature was found that reported on all these aspects of testing. Future examination of ecological effects of CNFs needs to consider measuring actual exposure concentrations by evaluating dispersibility and dispersion stability of CNFs.

The generalized linear model (GLM) is a useful tool to evaluate the relationship between the response variable and explanatory variables. However, the GLM analysis cannot consider the variation between experimental groups when the data shows over-dispersion of ecotoxicity testing data due to experimental replication. Alternatively, the generalized linear mixed model (GLMM) contains random effects which show a probability density distribution (in many cases, the Gaussian distribution is applied) attributed to the data variation. The GLMM can make a large variation by mixing the assumed probability density distribution with the fixed effects. To show the difference between GLM and GLMM analysis, we introduced two toxicity tests (Chironomus acute toxicity test in and mesocosm test) using dummy count data. The GLMM shows larger errors in the slope and intercept values than those in the GLM.

For the Chironomus acute toxicity test, the GLMM estimated large 95% confidence intervals for the EC₅₀ (median effective concentration) values, which could show the toxicity variations between the replications. Our findings suggested that the GLM analysis is likely to increase frequency of Type I error in estimating the relationship between variables if there is a large variation between the data.

The present study tested the early life stage toxicity of 3,5-dichlorophenol (3,5-DCP) on grass puffer, Takifugu niphobles, in order to evaluate its potential use as a marine fish model. The pufferfish embryos at 1-day post fertilization (dpf) were exposed to serially diluted 3,5-DCP at 20°C or 25°C until 14- or 10-dpf, respectively. Exposure to 3,5-DCP caused inhibition of pigmentation, of swimming, and of yolk absorption. The EC₅₀ of morphological abnormality and the LC₅₀ at the end of test were 0.97 and 1.4 mg/L at 25°C. The EC₅₀ and LC₅₀ values estimated at 20°C (0.75 and 0.79 mg/L, respectively) were generally similar to those at 25°C. The sensitivity to 3,5-DCP in the grass puffer was equivalent to those observed in other marine fish species. Because of the ease of handling and observation of embryos, and the high hatching and survival rates, we consider the grass puffer to be an ideal model for early-life stage toxicity testing.

We performed algal growth inhibition test on Desmodesmus subspicatus using a cationic surfactant benzalkonium bromide (BZK-Br), and acute toxicity tests on two cladoceran species, Daphnia galeata and Bosmina longirostris, using BZK-Br and an anionic surfactant sodium octyl sulfate (SOS). The 72-h 50% effective concentration (EC₅₀) with 95% confidence interval (CI) of initial BZK-Br to D. subspicatus was 60.3 µg L⁻¹ with 46.4–74.2 µg L⁻¹. The 48-h EC₅₀s (with those CIs) of BZK-Br to D. galeata and B. longirostris, estimated from the geometric mean concentrations, were 40.9 (33.0–48.8) µg L⁻¹ and 80.1 (68.1–92.0) µg L⁻¹, respectively. Unlike BZK-Br, the 48-h EC₅₀s (with those CIs) of SOS to D. galeata (335.9 mg L⁻¹, 248.5–423.3 mg L⁻¹) and B. longirostris (280.0 mg L⁻¹, 211.1–348.9 mg L⁻¹) were comparable. The present results were discussed about the difference in EC₅₀s to similar compounds on standard test organisms. We also mentioned that BZK-Br and SOS concentrations can present below the EC₅₀s in surface water, whereas they can affect biological interactions by interfering with colony formation response in D. subspicatus even at environmentally relevant concentrations.