We aimed to develop a growth inhibition test using Veronica undulata, a dicot aquatic plant. The examination was carried out using simetryn, 2,4–D, and 3,5–DCP as the test substances, to confirm the precision of the examination and sensitivity of Veronica undulata to herbicides. Directly post-germination, Veronica undulata was exposed to each test substance for seven days, and ErC₅₀ was calculated based on the growth speed of the leaf area or the dry weight. The coefficient of variation of ErC₅₀ for each test was less than 20%, and stable test results were obtained. In the growth inhibition test, the ErC₅₀ (μg/L) values of 2,4–D and 3,5–DCP were 585 and 3,394, and the sensitivity was at the same level as that by using Myriophyllum spicatum. These results suggest the possibility of using this test as a screening method for assessing the toxicity of chemical substances to dicot aquatic plants.

In the inner part of Isahaya Bay, Kyushu, western Japan, we assessed the biomaginification of total mercury (THg) in the benthic system. The sediment contained 133 ng/g d.w. of THg, which was about 4.9 times higher than particulate organic matter (POM) in the overlying water on the sediment. Both the primary and secondary consumers of the macro-benthic animals were divided into two groups in THg content, respectively. In the primary consumers, “High THg content group (101 ± 23 ng/g d.w.,mean ± S.D.)” consisted of animals that relied on the THg-contaminated sediment for diets and/or habitats. Its mean THg content was about 4.0 times higher than that of “Low THg content group” that occurred on the sediment surface or outside the sediment, and depended on diets suspended in the water. In the secondary consumers, “High THg content group (215 ± 47 ng/g d.w.)” were made up of crabs and sea star, which favored the animals (mainly clams) of “High THg content group” of the primary consumers for diets. Two different biomagnification pathways of THg existed in a single food chain of the macro-benthic communities.