There are some reports that transformation products of a pesticide exist at higher concentrations than their parent pesticide, or their pharmacological activities are comparable to that of a parent pesticide. It is therefore of importance to examine their potential effects on aquatic organisms; however, few studies have focused on the insecticidal activities of a transformation product of dinotefuran, a neonicotinoid pesticide. In this study, dinotefuran’s transformation products were explored by LC-HRMS analyses of dinotefuran aqueous solutions that had been irradiated by a xenon lamp. This exploration resulted in the discovery of two unknown transformation products. Structural elucidations of these two compounds suggested 28 and 82 chemical structures in terms of structural isomers and steric isomers, respectively. Their binding affinities for a glia-derived acetylcholine-binding protein of Lymnaea stagnalis were simulated to estimate their insecticidal activities. Out of 28 candidates, 20 were judged to have significant insecticidal activities. It can be concluded that the simulation of a substance’s binding affinity, the so-called docking simulation, is a promising way to exclude nontoxic substances among a large number of candidate substances.

Vegetation surveys with portable point positioning GPS devices were carried out for a specific alien plant, Ludwigia grandiflora subsp. hexapetala, at 132 communities on the shore of Lake Biwa from 2015 to 2016. The relationship between significant wave height and ground level where the alien plant grew was studied using a database of wind speed, wind direction, and effective fetch at six observation stations around Lake Biwa. The main results are as follows: 1) Ludwigia grandiflora subsp. hexapetala was not observed at communities with significant wave height was greater than 18 cm, 2) Ludwigia grandiflora subsp. hexapetala was observed at 55 communities. They were classified into four groups on the basis of the ground level where the alien plant was observed. The submerged type was found in 20 communities (from Biwako Surface Level (B.S.L.) -150 to -50 cm) . The emerged type was found in 14 communities (from B.S.L. -90 to -30 cm) . The ecotone type was found in 15 communities (from B.S.L. -50 to -30 cm) , and the land type was found in six communities (from B.S.L. -30 to -10 cm) , 3) The average significant wave height was 5.5 cm, 9.4 cm, and 13.2 cm, respectively, for submerged, emerged, and ecotone types. The significant wave height might be one of the factors governing the ground level at which the alien plant grows.

Essential fatty acids (EFAs) are used as an indicator of food source quality for animals. However, it is not clear whether the EFA composition of food sources is a good indicator of the abundance and richness of animals in ecosystems. In this study, field surveys of paddy fields were conducted to clarify the relationship between benthic animals and the EFA composition of sediment as a potential food source for those animals. We investigated sediment and benthic animals in several paddy fields in Miyagi prefecture from 2009 to 2011. We analyzed the EFA composition and Chl-a in sediment and identified the benthic animals present. We found a positive relationship (p < 0.05) between the concentration of 20:5ω3 in sediment and the number of families of benthic animals. It was considered that diatoms, widely known to be a producer of 20:5ω3, are diversity marker of benthic animals in paddy fields.