title: Terrestrial contributions to the aquatic food web in the middle Yangtze River.
abstract: Understanding the carbon sources supporting aquatic consumers in large rivers is essential for the protection of ecological integrity and for wildlife management. The relative importance of terrestrial and algal carbon to the aquatic food webs is still under intensive debate. The Yangtze River is the largest river in China and the third longest river in the world. The completion of the Three Gorges Dam (TGD) in 2003 has significantly altered the hydrological regime of the middle Yangtze River, but its immediate impact on carbon sources supporting the river food web is unknown. In this study, potential production sources from riparian and the main river channel, and selected aquatic consumers (invertebrates and fish) at an upstream constricted-channel site (Luoqi), a midstream estuarine site (Huanghua) and a near dam limnetic site (Maoping) of the TGD were collected for stable isotope (δ13C and δ15N) and IsoSource analyses. Model estimates indicated that terrestrial plants were the dominant carbon sources supporting the consumer taxa at the three study sites. Algal production appeared to play a supplemental role in supporting consumer production. The contribution from C4 plants was more important than that of C3 plants at the upstream site while C3 plants were the more important carbon source to the consumers at the two impacted sites (Huanghua and Maoping), particularly at the midstream site. There was no trend of increase in the contribution of autochthonous production from the upstream to the downstream sites as the flow rate decreased dramatically along the main river channel due to the construction of TGD. Our findings, along with recent studies in rivers and lakes, are contradictory to studies that demonstrate the importance of algal carbon in the aquatic food web. Differences in system geomorphology, hydrology, habitat heterogeneity, and land use may account for these contradictory findings reported in various studies.
authors.affiliation: Collaborative Innovation Center for Geo-hazards and Eco-environment in Three Gorges Area, Hubei Province, The Three Gorges University, Yichang, China.
authors.forename: Jianzhu
authors.initials: J
authors.lastname: Wang
authors.affiliation: Soil and Water Science Department, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Binhe
authors.initials: B
authors.lastname: Gu
authors.affiliation: Institute of Botany, the Chinese Academy of Sciences, Beijing, China.
authors.forename: Jianhui
authors.initials: J
authors.lastname: Huang
authors.affiliation: Institute of Applied Ecology, the Chinese Academy of Sciences, Shenyang, China.
authors.forename: Xingguo
authors.initials: X
authors.lastname: Han
authors.affiliation: Center for Earth System Science, Tsinghua University, Beijing, China.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Lin
authors.affiliation: Nanjing Research Institute of Hydrology and Water Resources, Nanjing, China.
authors.forename: Fawen
authors.initials: F
authors.lastname: Zheng
authors.affiliation: Soil and Water Science Department, Tropical Research and Education Center, IFAS, University of Florida, Homestead, Florida, United States of America.
authors.forename: Yuncong
authors.initials: Y
authors.lastname: Li
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000737:chemistry / Q000502:physiology; D002247:Carbon Isotopes / Q000032:analysis; D002681:China; D017753:Ecosystem; D004784:Environmental Monitoring; D005399:Fishes / Q000502:physiology; D020387:Food Chain; D007448:Invertebrates / Q000737:chemistry / Q000502:physiology; D009587:Nitrogen Isotopes / Q000032:analysis; D018521:Plant Physiological Phenomena; D010944:Plants / Q000737:chemistry; D045483:Rivers / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes