Variation in nitrogen isotopic composition in the Selenga river watershed, Mongolia

Fujio Hyodo, Junko Nishikawa, Ayato Kohzu, Noboru Fujita, Izuru Saizen, Jamsran Tsogtbaatar, Choijilsuren Javzan, Mangaa Enkhtuya, Davaadorj Gantomor, Narantsetsegiin Amartuvshin, Reiichiro Ishii, Eitaro Wada

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


The stable nitrogen (N) isotope ratio (δ 15N) has been used to examine the anthropogenic N input (i. e., septic water, wastewater, and manure) to aquatic ecosystems, because anthropogenic N generally has a δ 15N signature distinct from that found in nature. Aquatic organisms and the derived organic matter such as sediments are reported to become increasingly enriched in 15N as the human population density increases in watersheds. However, little is known about the relationship in steppe ecosystems, where the livestock population is greater than that of humans. Here, we conducted a preliminary study in the Selenga river mainstream watershed in Mongolia, which covers an area of approximately 300,000 km 2. A multiple regression analysis revealed that the δ 15N of the riverine sediment was significantly affected by the human population density and more significantly by livestock population density. The population density, including both humans and livestock, significantly influenced δ 15N of the macrophytic Potamogeton spp. The results showed that δ 15N of riverine organic matter can be an indicator of the human and livestock population density, which is likely associated with the status of N cycles in livestock-dominated watersheds.

Original languageEnglish
Pages (from-to)155-161
Number of pages7
Issue number1
Publication statusPublished - Apr 2012


  • Livestock
  • Mongolia
  • Population
  • Stable N isotope ratio
  • Watershed

ASJC Scopus subject areas

  • Ecology
  • Aquatic Science
  • Water Science and Technology


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