Recently, quantitative analyses of food web structure based on carbon and nitrogen stable isotopes are widely applied to environmental assessments as well as ecological researches of various ecosystems, particularly rivers and streams. In the present study, we analyzed carbon and nitrogen stable isotope ratios of POM (both planktonic and attached forms), zooplankton, benthic macroinvertebrates and fish collected from 6 sites located at Nakdong River. Samples were collected from upstream areas of 5 weirs (Sangju, Gangjeong- Goryeong, Dalseong, Hapcheon-Changnyeong, and Changnyeong-Haman Weirs) and one downstream area of Hapcheon-Changnyeong Weir in dry season (June) and after rainy season (September). We suggested ranges of their carbon and nitrogen stable isotope ratios and calculated their trophic levels in the food web to compare their temporal and spatial variations. Trophic levels of organisms were relatively higher in Sangju Weir located at upper part of Nakdong River, and decreased thereafter. However, the trophic levels were recovered at the Changnyeong-Haman Weir, the lowest weir in the river. The trophic level calculated by nitrogen stable isotope ratios showed more reliable ranges when they were calculated based on zooplankton than POM used as baseline. The suggested quantitative ecological information of the majority of biological communities in Nakdong River would be helpful to understand the response of river food web to environmental disturbances and can be applied to various further researches regarding the quantitative approaches for the understanding food web structure and function of river ecosystems as well as restoration.

Abstract
 서 론
 재료 및 방법
  1. 조사지점 및 시기
  2. 기초 수질
  3. 유기물 및 생물시료 채집
  4. 안정동위원소 분석과 영양단계 (trophic level) 산출
 결과 및 고찰
  1. 수질
  2. 분류군별 탄소 및 질소 안정동위원소 비
  3. 분류군별 탄소 안정동위원소 비의 시공간 분포
  4. 분류군별 영양단계 (trophic level)의 시공간 분포
  5. 영양단계 산출 기준 선정의 중요성
 적 요
 REFERENCES

• 오혜지(경희대학교 환경학및환경공학과) | Hye-Ji Oh (Department of Environmental Science and Engineering, Kyung Hee University)
• Jin Mei-Yan(경희대학교 환경학및환경공학과) | Mei-Yan Jin (Department of Environmental Science and Engineering, Kyung Hee University)
• 최보형(한양대학교 해양융합과학과) | Bohyung Choi (Department of Marine Sciences and Convergent Technology, Hanyang University)
• 신경훈(한양대학교 해양융합과학과) | Kyung-Hoon Shin (Department of Marine Sciences and Convergent Technology, Hanyang University)
• 나긍환(순천대학교 환경교육과) | Geung-Hwan La (Department of Environmental Education, Sunchon National University)
• 김현우(순천대학교 환경교육과) | Hyun-Woo Kim (Department of Environmental Education, Sunchon National University)
• 장민호(공주대학교 생물교육과) | Min-Ho Jang (Department of Biology Education, Kongju National University)
• 이경락(국립환경과학원) | Kyung-Lak Lee (Watershed Ecology Research Team, National Institute of Environmental Research)
• 장광현(경희대학교 환경학및환경공학과) | Kwang-Hyeon Chang (Department of Environmental Science and Engineering, Kyung Hee University) Corresponding author