10:00 AM - 10:15 AM
[HTT16-10] Insights of the aquatic ecosystem in Lake Suwa using compound-specific isotope ratio analysis
Keywords:Aquatic ecosystem, Lake Suwa, Stable isotope ratio analysis, Compound-specific isotope analysis of Amino Acids
Lake Suwa is a fault lake located on the Itoigawa-Shizuoka Tectonic Line and has a large catchment area (531 km2) that is approximately 40 times the size of the lake. The catchment area includes mountainous and densely populated areas as well as rice paddies and fields. Therefore, the water quality of the lake has been strongly influenced by human activities. Since the 1970s, cyanobacterial bloom has occurred during the summer in the lake because of the influx of nutrients from the surrounding area. However, water quality has improved with the spread of sewage systems, and no large-scale cyanobacterial blooms have been observed since 1998. On the other hand, Wakasagi, an important fishery resource in the lake, has been on a decreasing trend in catch in recent years.
Lake Suwa has been continuously studied for water quality and aquatic ecosystems for a long time. In particular, the lake is one of the longest-studied lakes in Japan in terms of ecosystems, and the isotope ratio-based analysis method was conducted in the first phase of research on food web analysis in Japan [1]. This method can estimate the trophic levels in an ecological pyramid by measuring the isotope ratios of organisms [2]. The food web in an ecosystem is important information for understanding the ecosystem, which is also extremely useful for the maintenance and conservation of the ecosystem. In recent years, methods for estimating trophic levels by nitrogen isotope ratio analysis of amino acids have improved the accuracy of trophic level estimation [3].
Since 30 years have passed since the first study using isotope ratios in Lake Suwa, the environment of the lake, including its ecosystem, has changed drastically. In this study, food web analysis was conducted for all aquatic organisms in Lake Suwa using the trophic level estimation method based on nitrogen isotope ratios of amino acids, and the results were compared with those obtained in the 1980s when cyanobacterial blooms were occurring.
This study was supported in part by the Japan Society for the Promotion of Science (JSPS) with the joint research between the JAMSTEC and Shinshu University.
[1] Yoshioka et al. (1994) A stable isotope study on seasonal food web dynamics in a eutrophic lake. Ecology, 75, 835-846.
[2] Minagawa M. & Wada E. (1984) Stepwise enrichment of 15N along food chains: Further evidence and the relation between δ15N and animal age. Geochimica et Cosmochimica Acta, 48, 1135-1140.
[3] Ohkouchi et al. (2017) Advances in the application of amino acid nitrogen isotopic analysis in ecological and biogeochemical studies. Organic Geochemistry, 113, 150-174.
Lake Suwa has been continuously studied for water quality and aquatic ecosystems for a long time. In particular, the lake is one of the longest-studied lakes in Japan in terms of ecosystems, and the isotope ratio-based analysis method was conducted in the first phase of research on food web analysis in Japan [1]. This method can estimate the trophic levels in an ecological pyramid by measuring the isotope ratios of organisms [2]. The food web in an ecosystem is important information for understanding the ecosystem, which is also extremely useful for the maintenance and conservation of the ecosystem. In recent years, methods for estimating trophic levels by nitrogen isotope ratio analysis of amino acids have improved the accuracy of trophic level estimation [3].
Since 30 years have passed since the first study using isotope ratios in Lake Suwa, the environment of the lake, including its ecosystem, has changed drastically. In this study, food web analysis was conducted for all aquatic organisms in Lake Suwa using the trophic level estimation method based on nitrogen isotope ratios of amino acids, and the results were compared with those obtained in the 1980s when cyanobacterial blooms were occurring.
This study was supported in part by the Japan Society for the Promotion of Science (JSPS) with the joint research between the JAMSTEC and Shinshu University.
[1] Yoshioka et al. (1994) A stable isotope study on seasonal food web dynamics in a eutrophic lake. Ecology, 75, 835-846.
[2] Minagawa M. & Wada E. (1984) Stepwise enrichment of 15N along food chains: Further evidence and the relation between δ15N and animal age. Geochimica et Cosmochimica Acta, 48, 1135-1140.
[3] Ohkouchi et al. (2017) Advances in the application of amino acid nitrogen isotopic analysis in ecological and biogeochemical studies. Organic Geochemistry, 113, 150-174.