Initial response of fish trophic niche to hydrological alteration in the upstream of Three Gorges Dam

Lei Li,Jianzhu Wang,Jun Xu,Binhe Gu

doi:10.1186/s13717-016-0055-3

Abstract

Damming is one of the dramatic impacts to river food webs due to habitat fragmentation and changes in the hydrological regimes. The world’s largest dam, the Three Gorges Dam (TGD), has been constructed in the middle of Yangtze River since 2003. The objective of this study was to understand the effects of altered hydrological regime on the trophic structure of fish food web along the hydrological gradient in the TGD. Fish samples were collected from an upstream, a midstream and a downstream site of the Yangtze River upstream of the TGD in May and September of 2004. Muscle tissue of each fish species was determined for stable isotopic compositions (δ13C and δ15N) which were used to calculate isotope-based Bayesian community-wide trophic metrics. Stable isotope trophic niche analysis reveals reduced utilization of basal resource and trophic niche space at the midstream and downstream sites. By contrast, community trophic diversity and species redundancy were higher at the downstream than the upstream and midstream, likely as the result of reduced the spectrum of basal resources. These findings suggested that the negative impacts on the overall trophic niche space from reduced flow, increased water depth and stagnancy occurred only one year after the completion of the TGD. Altered hydrological regimes posed multiple impacts to the aquatic food web. Reduced flow and increased water depth within TGD has posed initial effects to the fish community trophic structure. Further collections ana analysis of ecological data to compare the fish trophic structure revealed in this study are needed to assess the long-term impacts of TGD on fish community structure and resources utilization.

Highlights

Damming is one of the dramatic impacts to river food webs due to habitat fragmentation and changes in the hydrological regimes
The hydrological flow rate before the construction of the Three Gorges Dam (TGD) was high across the study sites (Wang et al 2014) but was greatly reduced after the completion of the dam to nearly stagnant at the downstream site
A total of 27 fish species were collected from the three study sites with species abundance highest at the upstream (22 species), moderate at downstream (14), and lowest at midstream (12)

Summary

Introduction

Damming is one of the dramatic impacts to river food webs due to habitat fragmentation and changes in the hydrological regimes. The world’s largest dam, the Three Gorges Dam (TGD), has been constructed in the middle of Yangtze River since 2003. Damming leads to habitat fragmentation, changes in water depth, alter the rates, seasonal timing, and durations of flow. These changes may in turn affect the physical, chemical, and biological features of the river systems (Sternberg 2006; Dudgeon 2011). The construction of the Three Gorges Dam (TGD) at the middle of Yangtze River in south-central China would have a series of environmental consequences (Wu et al 2003; Fu et al 2003; Xu et al 2013). The formerly narrow channel with torrential water flow has been converted to extensive stagnant water similar to the limnetic zone of a large lake system as increases in the water depth, alternations of hydrology, and other physical, chemical, and biological characteristics of Three Gorges Reservoir (TGR) and the downstream (Liu and Cao 1992; Salazar 2000; Wu et al 2003; Xu et al 2013)

Objectives

Methods

Results

Discussion

Conclusion