[H-TT16] Development and application of environmental traceability methods

[HTT16-06] Estimate the origin of nutrients supplied to coastal areas using Ulva pertusa's nitrogen and carbon stable isotope ratios.

*Tatsuhiro Ishida¹, Osamu Tominaga¹, Ryo Sugimoto¹, Naoki Kisa¹, Keisuke Koba², Keitaro Fukushima² (1.Fukui Prefectural University, 2.Center for Ecological Research,Kyoto University)

Keywords:δ15N, δ13C, environmental tracer

In recent years, attention is focused on various problems caused by nutrients flowing into coastal areas. However, there is little specific knowledge about how the influx of nutrients is incorporated into coastal ecosystems. In this study, in order estimate the contribution of nutrients of multiple origins to primary producers, we recorded fluctuations in the stable nitrogen and carbon isotope ratio through a culture experiment of Ulva pertusa in Obama Bay, Fukui Prefecture. We conducted Ulva pertusa culture experiments four times in July-August 2018, October-November, April-May 2019, and September-October in Obama Bay and the laboratory outdoor aquarium. The maximum culture period was 25 days. Finally, the stable nitrogen and carbon isotope ratio were measured, and the fluctuation of the isotope ratio was verified through the culture experiment. Fluctuations in the nitrogen and carbon stable isotope ratios of Ulva pertusa were confirmed through culture experiments. Ulva pertusa placed in nutrient environments of different origins had large fluctuations in isotope ratio from the first day of culture, and the error between cultured individuals was small. Our results suggest that Ulva pertusa can be used to estimate the origin of nutrients.