Photo-production of excited triplet-state of dissolved organic matters in inland freshwater and coastal seawater.

The excited triplet-state of dissolved organic matter (3DOM*) is a major reactive intermediate in sunlit waters. Its quantum yield is important in understanding the fate of organic micropollutants. The degradation efficiency of its chemical probe, 2,4,6-trimeythlphenol (fTMP), is generally used as a proxy of the quantum yield. However, fTMP has been described and modelled only for freshwater systems. Therefore, this study quantified fTMP in inland freshwater and coastal seawater sampled in Japan by conducting steady-state photochemical experiments. Optical properties of water were then used to model fTMP. Results indicated that the inland freshwater DOM originated mainly from terrestrial sources, while the coastal seawater DOM were microbial-dominated. On average, inland freshwater exhibited lower fTMP (61.2 M-1) than coastal seawater (79.7 M-1) and the coastal seawater exhibited significant variations in the proportion of high-energy 3DOM* (> 250 kJ/mol). In addition, E2:E3 (ratio of absorbance at 254 to 365 nm) was positively correlated with fTMP of inland freshwater, coastal seawater, and the overall dataset. Catchment conditions such as forest coverage also influenced the production of 3DOM* and high-energy 3DOM* in inland freshwater. Furthermore, the developed models estimated fTMP based on the optical properties of both freshwater and seawater, providing valuable insights about 3DOM* photochemistry in the aquatic environment.

Development of microsatellite markers for a soricid water shrew, Chimarrogale platycephalus, and their successful use for individual identification.

The soricid water shrew Chimarrogale platycephalus is a mammalian species endemic to the Japanese Islands. The animals inhabit the islands of Honshu and Kyushu, and are considered to be extinct in Shikoku. Information on this water shrew from Honshu and Kyushu is scarce, and C. platycephalus is registered on many local governments' red lists as an endangered species. There are very few studies on their ethology, ecology or phylogenetics, due to difficulties related to the shrews being both nocturnal and aquatic: to study C. platycephalus, field research must be conducted in mountain streams at night. To overcome these challenges, we previously established a genetic analysis method using the feces of C. platycephalus, as a result of which the amount of phylogenetic and phylogeographic data has increased and our understanding of the species has improved. In this study, microsatellite markers were developed, and analyses using markers for 21 loci were performed. Moreover, to confirm the ability of these 21 microsatellite markers to differentiate individuals, all markers were tested using fecal and tissue specimens from 12 individuals reared separately in an aquarium. Using as few as 12 of these loci, individual differentiation with 100% accuracy should be achievable. The development of microsatellite markers in this study and the establishment of individual identification methods should greatly contribute to future ecological, ethological, population genetics and biogeographical research on C. platycephalus.

Effects of sampling seasons and locations on fish environmental DNA metabarcoding in dam reservoirs.

Environmental DNA (eDNA) analysis has seen rapid development in the last decade, as a novel biodiversity monitoring method. Previous studies have evaluated optimal strategies, at several experimental steps of eDNA metabarcoding, for the simultaneous detection of fish species. However, optimal sampling strategies, especially the season and the location of water sampling, have not been evaluated thoroughly. To identify optimal sampling seasons and locations, we performed sampling monthly or at two-monthly intervals throughout the year in three dam reservoirs. Water samples were collected from 15 and nine locations in the Miharu and Okawa dam reservoirs in Fukushima Prefecture, respectively, and five locations in the Sugo dam reservoir in Hyogo Prefecture, Japan. One liter of water was filtered with glass-fiber filters, and eDNA was extracted. By performing MiFish metabarcoding, we successfully detected a total of 21, 24, and 22 fish species in Miharu, Okawa, and Sugo reservoirs, respectively. From these results, the eDNA metabarcoding method had a similar level of performance compared to conventional long-term data. Furthermore, it was found to be effective in evaluating entire fish communities. The number of species detected by eDNA survey peaked in May in Miharu and Okawa reservoirs, and in March and June in Sugo reservoir, which corresponds with the breeding seasons of many of fish species inhabiting the reservoirs. In addition, the number of detected species was significantly higher in shore, compared to offshore samples in the Miharu reservoir, and a similar tendency was found in the other two reservoirs. Based on these results, we can conclude that the efficiency of species detection by eDNA metabarcoding could be maximized by collecting water from shore locations during the breeding seasons of the inhabiting fish. These results will contribute in the determination of sampling seasons and locations for fish fauna survey via eDNA metabarcoding, in the future.