We compared stage-dependent sensitivities of the sea urchin Anthocidaris crassispina to silver nitrate (AgNO₃) and silver nanocolloids (SNCs). Our experimental design included three different exposure experiments: (1) pre-fertilization exposures (to assess effects on first cleavage and embryogenesis); (2) exposures of fertilized eggs (to assess effects on cleavage and embryogenesis); and (3) exposures of gastrulae (to assess effects on the gastrula stage and embryogenesis). In the case of the pre-fertilization exposures, exposure of sperm to SNCs induced higher rates of abnormal development than did exposure to AgNO₃, and SNCs had higher teratogenicity on pluteus formation than did AgNO₃. In the case of the fertilized egg exposures, exposed embryos experienced high rates of cytolysis. These rates exceeded those observed in pre-fertilization exposures of eggs and sperm and were similar to those observed in exposures of sperm alone. In the case of the gastrula exposures, rates of cytolysis were higher than those observed in pre-fertilization exposures of eggs and sperm and lower than those observed in exposures of fertilized eggs and of sperm alone. Sperm exposures showed the highest chemical sensitivity, followed by exposures of gastrulae and of unfertilized eggs and sperm.

The effect of herbicides on attached diatom communities was investigated to understand the differences in species sensitivity and the applicability of diatom-based metrics. Diatom community collected from the natural environment was exposed to seven herbicides with various modes of action for three days in a controlled laboratory condition. Five genera of diatom dominating in the control experiment were subjected to the data analysis. The order of sensitivity to herbicides did not differ markedly among herbicides: Fragilaria ≒ Achnanthidium > Navicula ≒ Planothidium > Nitzschia. The result that the difference in species sensitivity was not specific to the mode of action suggests the possibility of a simple classification into herbicide sensitive/tolerant species. Then, several biological metrics for species composition were calculated such as genus number and Shannon's diversity. SPEAR_herbicides as an indicator of the herbicide effect on the diatom community was less detectable. Instead, a modified SPEAR index based on the present study would be a better indicator of the herbicide effect on the diatom community.

We conducted algal toxicity test of non-surface-coated silver nanocolloids (SNCs) using Raphidocelis subcapitata. The materials tested and growth medium (COMBO medium) used in the present study were the same as those in our previous bioassays for cladocerans. The 10% and 50% effective concentrations (72-h EC₁₀ and EC₅₀) with 95% confidence intervals for algal growth rate were 16.1 (12.8–19.3) µg/L and 43.4 (39.2–47.6) µg/L, respectively. We found that those endpoint values did not differ largely from the chronic endpoint values for Daphnia magna (e.g., EC₁₀ for net reproductive rate was 20.9 µg/L), indicating those organisms have similar vulnerability to SNCs.

This study was performed to investigate the occurrence of selected insecticides (seven neonicotinoid insecticides and their four metabolites and the phenylpyrazole insecticide fipronil) in Hiuchi-Nada (48 samples) and Osaka Bay (4 samples), Seto Inland Sea, Japan, in 2016 and 2017. Among the insecticides examined, dinotefuran was exclusively detected in both the bays. Its concentration (9.45 and 32.4 ng/L in Hiuchi-Nada and Osaka Bay, respectively) and detection frequency (68.8% and 75.0% in Hiuchi-Nada and Osaka Bay, respectively) were the highest in September, which were closely related to its agricultural application. Furthermore, we observed a higher concentration of the insecticide in the surface layer of the water column than in the bottom layer. Considering that the water temperature was constant through the water column in September, insecticides were transported to estuarine areas and were eventually distributed around the surface waters of the bays. Finally, we inferred that the ecological risks posed by dinotefuran in the bay areas were expected to be too low to cause adverse effects on the resident estuarine and marine crustaceans examined.