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  • P-ISSN2765-2203
  • E-ISSN2765-2211

Stable Carbon Isotope Signature of Dissolved Inorganic Carbon (DIC) in Two Streams with Contrasting Watershed Environments: A Potential Indicator for Assessing Stream Ecosystem Health

Proceedings of the National Institute of Ecology of the Republic of Korea, (P)2765-2203; (E)2765-2211
2021, v.2 no.4, pp.259-273
https://doi.org/10.22920/PNIE.2021.2.4.259
Chulgoo Kim (National Institute of Ecology)
Jong-Yun Choi (National Institute of Ecology)
Byungwoong Choi (National Institute of Environmental Research)
JunSeok Lee (National Institute of Ecology)
Yonglak Jeon (National Institute of Ecology)
Taewoo Yi (National Institute of Ecology)

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Abstract

We conducted a study to investigate the characteristics of the carbon cycle of two streams (located in Shiga Prefecture, Japan), having similar size, namely, the Adokawa stream (length: 52 km, area: 305 km2, watershed population: 8,000) and the Yasukawa stream (length: 62 km, area: 380 km2, watershed population: 120,000), but with different degree of human activity. Samples were collected from these two streams at 14 (Adokawa stream) and 23 (Yasukawa stream) stations in the flowing direction. The dissolved inorganic carbon (DIC) concentration and the stable carbon isotope ratio of DIC (δ13C-DIC) were measured in addition to the watershed features and the chemical variables of the stream water. The δ13C-DIC (-9.50 ± 2.54‰), DIC concentration (249 ± 76 μM), and electric conductivity (52 ±13 μS/cm) in Adokawa stream showed small variations from upstream to downstream. However, the δ13C-DIC (-8.68 ± 2.3‰) upstream of Yasukawa stream was similar to that of Adokawa stream and decreased downstream (-12.13 ± 0.43‰). DIC concentration (upstream: 272 ± 89 μM, downstream: 690 ± 37 μM) and electric conductivity (upstream: 69 ± 17 μS/cm, downstream: 193 ± 37 μS/cm) were higher downstream than upstream of Yasukawa stream. The DIC concentration of Yasukawa stream was significantly correlated with watershed environmental variables, such as, watershed population density (r = 0.8581, p<0.0001, n = 23), and forest area percentage of the watershed (r = -0.9188, p<0.0001, n = 23). δ13C-DIC showed significant negative correlation with the DIC concentration (r = -0.7734, p<0.0001, n = 23), electric conductivity (r = -0.5396, p = 0.0079, n = 23), and watershed population density (r = -0.6836, p = 0.0003, n = 23). Our approach using a stable carbon isotope ratio suggests that DIC concentration and δ13C-DIC could be used as indicators for monitoring the health of stream ecosystems with different watershed characteristics.

Submission Date
2021-06-30
Revised Date
2021-10-07
Accepted Date
2021-10-08

Proceedings of the National Institute of Ecology of the Republic of Korea