Food Web Structure and Trophic Interactions Revealed by Stable Isotope Analysis in the Midstream of the Chishui River, a Tributary of the Yangtze River, China

Understanding energy flow and nutrient pathways is crucial to reveal the dynamics and functions of riverine ecosystems and develop appropriate conservation strategies. In this study, we utilized stable isotopes of δ13C and δ15N to examine the fundamental characteristics of trophic position, trophic niche, and carbon source for the food web in the midstream of the Chishui River, a tributary to the Yangtze River. Our results showed that stable isotope signatures among different sorts of basal resources and consumers were significantly distinguishable and that the food chain consisted of four trophic levels, indicating the multiple trophic pathways and long food chain length here. The trophic guilds of fish were classified into four categories, in which herbivorous and carnivorous fish showed greater trophic diversity and omnivorous fish had higher trophic redundancy, which meant that there was a stable trophic niche structure in the study area. Phytoplankton and periphyton presented the largest contributions to consumers, indicating that autochthonous productivity was the dominant carbon source in the midstream of the Chishui River. Since the Chishui River is still in a natural condition without any dam constructions, the autochthonous productivity, stable trophic niche structure, multiple trophic pathways and long food chain length found here demonstrate its high conservation value. Therefore, the strategy to refrain from damming on this river should persist into the future.

Download Full-text

Food Chain Length Associated with Environmental Factors Affected by Large Dam along the Yangtze River

Water ◽

10.3390/w12113157 ◽

2020 ◽

Vol 12 (11) ◽

pp. 3157

Author(s):

Chun He ◽

Huatang Deng ◽

Jiawen Ba ◽

Sheng Li ◽

Zheyu Chen ◽

...

Keyword(s):

Chain Length ◽

Food Chain ◽

Yangtze River ◽

Main Stream ◽

The Yangtze River ◽

Ecosystem Size ◽

Food Chain Length ◽

Critical Measure ◽

Model Weight ◽

Food Web Complexity

Food chain length (FCL) is a critical measure of food web complexity that influences the community structure and ecosystem function. The FCL of large subtropical rivers affected by dams and the decisive factors are far beyond clear. In this study, we used stable isotope technology to estimate the FCL of fish in different reaches of the main stream in the Yangtze River and explored the key factors that determined the FCL. The results showed that FCL varied widely among the studied areas with a mean of 4.09 (ranging from 3.69 to 4.31). The variation of FCL among river sections in the upstream of the dam was greater than that in the downstream. Regression analysis and model selection results revealed that the FCL had a significant positive correlation with ecosystem size as well as resource availability, and FCL variation was largely explained by ecosystem size, which represented 72% of the model weight. In summary, our results suggested that ecosystem size plays a key role in determining the FCL in large subtropical rivers and large ecosystems tend to have a longer food chain. Additionally, the construction of the Three Gorges Dam has been speculated to increase the FCL in the impoundment river sections.

Download Full-text

Trophic structure of a nektobenthic community exploited by a multispecific bottom trawling fishery in Northeastern Brazil

PLoS ONE ◽

10.1371/journal.pone.0246491 ◽

2021 ◽

Vol 16 (2) ◽

pp. e0246491

Author(s):

Alex Souza Lira ◽

Flávia Lucena-Frédou ◽

Frédéric Ménard ◽

Thierry Frédou ◽

Júlio Guazzelli Gonzalez ◽

...

Keyword(s):

Stable Isotope ◽

Food Web ◽

Benthic Invertebrates ◽

Trophic Structure ◽

Fish Fauna ◽

Cumulative Effects ◽

Northeastern Brazil ◽

Population Parameters ◽

Bottom Trawling ◽

Trophic Pathways

We used complementary stable isotope (SIA) and stomach content (SCA) analyses to investigate feeding relationships among species of the nektobenthic communities and the potential ecological effects of the bottom trawling of a coastal ecosystem in northeastern Brazil. Carbon (δ13C) and nitrogen (δ15N) compositions were determined for five basal sources and 28 consumers, from zooplankton to shrimp and fish species. Fishes and basal sources showed a broad range of δ15N (fishes: 6.49–14.94‰; sources: 2.58–6.79‰) and δ13C values (fishes: -23.86 to -13.71‰; sources: -24.32 to -13.53‰), while shrimps and crabs exhibited similar nitrogen and carbon ratios. Six trophic consumer groups were determined among zooplankton, crustaceans and fishes by SIA, with trophic pathways associated mostly with benthic sources. SCA results indicated a preference for benthic invertebrates, mainly worms, crabs and shrimps, as prey for the fish fauna, highlighting their importance in the food web. In overall, differences between SCA and the SIA approaches were observed, except for groups composed mainly for shrimps and some species of high δ15N values, mostly piscivorous and zoobenthivores. Given the absence of regulation for bottom trawling activities in the area, the cumulative effects of trawling on population parameters, species composition, potentially decreasing the abundance of benthic preys (e.g., shrimps, worms and crabs) may lead to changes in the trophic structure potentially affect the food web and the sustainability of the fishery.

Download Full-text

Long-term variation in isotopic baselines and implications for estimating consumer trophic niches

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f08-125 ◽

2008 ◽

Vol 65 (10) ◽

pp. 2191-2200 ◽

Cited By ~ 19

Author(s):

Christopher T. Solomon ◽

Stephen R. Carpenter ◽

James A. Rusak ◽

M. Jake Vander Zanden

Keyword(s):

Stable Isotope ◽

Food Web ◽

Isotope Ratios ◽

Trophic Niche ◽

Accurate Estimation ◽

Stable Isotope Ratios ◽

Turnover Rates ◽

C And N ◽

Trophic Niches

Carbon and nitrogen stable isotope ratios are increasingly used to study long-term food web change. Temporal variation at the base of the food web may impact the accuracy of trophic niche estimates, but data describing interannual baseline variation are limited. We quantified baseline variation over a 23-year period in a north-temperate lake and used a simulation model to examine how this variation might affect consumer trophic niche estimates. Interannual variation in C and N stable isotope ratios was significant for both benthic and pelagic primary consumer baselines. Long-term linear trends and shorter-term autoregressive patterns were apparent in the data. There were no correlations among benthic and pelagic C and N baselines. Simulations demonstrated that error in estimated fish trophic niches, but not bias, increased substantially when sampling of baselines was incomplete. Accurate trophic niche estimates depended more on accurate estimation of baseline time series than on accurate estimation of growth and turnover rates. These results highlight the importance of previous and continued efforts to constrain bias and error in long-term stable isotope food web studies.

Download Full-text