Nitrogen-stable isotopic signatures of basal food items, primary consumers and omnivores in rivers with different levels of human impact

Ayato Kohzu, Ichiro Tayasu, Chikage Yoshimizu, Atsushi Maruyama, Yukihiro Kohmatsu, Fujio Hyodo, Yukio Onoda, Akitake Igeta, Kiyoshi Matsui, Takanori Nakano, Eitaro Wada, Toshi Nagata, Yasuhiro Takemon

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

We examined how nitrogen-stable isotopic signatures of food web components (basal resources, primary and lower consumers, and omnivores) in rivers change with increasing levels of human population density (HPD) in their watersheds. Samples were collected from 22 rivers flowing in the Lake Biwa basin, Japan. Among three potential resources at the base of food webs (epilithon, benthic and suspended particulate organic matter), the mean isotopic values (δ15N) of the epilithon (4.5-7.8%) were consistently higher than those of other items (1.9-4.2%) and displayed the most pronounced elevation (by 3.3%) with increasing HPD. The mean δ15N values of the individual taxa of lower consumers (bivalve, snail and caddisfly) tended to increase with increasing HPD, although the pattern and the extent of the elevation were highly variable among the taxa. These results suggest a taxon-specific feature in the N source (or sources) of lower consumers. Our data suggested that human activities (e.g. nutrient loading) potentially induce changes in the N baselines of river food webs. The major N source of bivalves appeared to be shifted from suspended particulate organic matter to other items with increasing HPD. Trophic levels of goby fish (Rhinogobius sp. OR) and shrimp (Palaemon paucidens), being estimated to be at 2.4-3.8 and 2.1-3.4, respectively, did not differ significantly among rivers with different HPD levels.

Original languageEnglish
Pages (from-to)127-136
Number of pages10
JournalEcological Research
Volume24
Issue number1
DOIs
Publication statusPublished - Jan 2009
Externally publishedYes

Keywords

  • Food web
  • Human impact
  • River
  • Stable isotope
  • Trophic level

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

Fingerprint Dive into the research topics of 'Nitrogen-stable isotopic signatures of basal food items, primary consumers and omnivores in rivers with different levels of human impact'. Together they form a unique fingerprint.

  • Cite this

    Kohzu, A., Tayasu, I., Yoshimizu, C., Maruyama, A., Kohmatsu, Y., Hyodo, F., Onoda, Y., Igeta, A., Matsui, K., Nakano, T., Wada, E., Nagata, T., & Takemon, Y. (2009). Nitrogen-stable isotopic signatures of basal food items, primary consumers and omnivores in rivers with different levels of human impact. Ecological Research, 24(1), 127-136. https://doi.org/10.1007/s11284-008-0489-x