Stable Isotope Analysis Reveals the Importance of Riparian Resources as Carbon Subsidies for Fish Species in the Daning River, a Tributary of the Three Gorges Reservoir, China

The patterns of carbon flow in large rivers influenced by dams are still not well known. We hypothesized that spatial variation in fish assimilation of basal production sources would be affected by heterogeneity of landscape-scale hydrology within a watershed due to the impoundment. We used stable isotope analysis and Bayesian mixing models to estimate relative contributions of basal production sources to fish consumers in a tributary of the Three Gorges Reservoir (TGR) with remarkably heterogeneous habitats between the upper and lower reaches. Model estimates indicated that riparian C3 plants were the main basal food source irrespective of reaches or feeding groups. Autochthonous algae carbon also appeared to be important as secondary carbon sources. However, the major contributive aquatic algae in the upstream were benthic algae while planktonic algae were important in the downstream, and this difference was related to their distinct hydrological characteristics. The contribution from C4 plants was comparatively less important to all fish consumers. Our results highlighted the significance of the riparian C3 carbon source to fish consumers in the TGR tributary and that the difference in landscape-scale characteristics was not enough to influence the pattern, which may be attributed to abundant standing stock of the riparian plants as well as hydrologic regimes in this river

Improvement of the mechanical and tribological behaviors by Ti-C interlayer for diamond-like carbon films on nitrile butadiene rubber

To improve the mechanical and tribological properties of diamond-like carbon (DLC) film on nitrile butadiene rubber, the DLC/Ti-C bilayer films are fabricated by a dual-target magnetron sputtering method. The morphological characterization results indicate that the roughness of DLC/Ti-C first decreases and then increases slightly with the increase of Ti content and surface roughness of all modified samples is lower than that of nitrile butadiene rubber (NBR). Raman spectra show that the change of Ti content in the Ti-C interlayer has no effect on the ratio of sp2 to sp3 bonds of surface DLC film. The nanoindentation results show that the Ti content significantly affects the hardness, Young’s modulus, hrex/hmax and elastic recovery (%). Notably, the DLC/Ti-C films with a Ti content of 12.32 ∼ 14.77 at. % show the lowest coefficient of friction (CoF, 0.1 ∼ 0.2) and superior wear resistance due to the increased transformation of sp2 into sp3 in the films. This study unravels that the DLC films' superior mechanical and tribologic performance could be realized by regulating the Ti content in the Ti-C interlayer

Effect of titanium suboxide on the formation of anatase and rutile phases during annealing of C-Doped Ti-O thin film deposited by DC magnetron sputtering

C-doped Ti-O films with different titanium suboxide contents are prepared by DC magnetron sputtering deposition at different sputtering powers. The films with different phases are formed after annealing at 873 K in air. The structure of the films is characterized by X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. The optical properties and surface roughness of the films are investigated by UV-vis spectroscopy and atomic force microscopy, respectively. Photocatalytic activity of the thin films is studied by degrading the methyl orange solution under xenon lamp (300 W) irradiation. The results show that the C-doped Ti-O thin films with higher titanium suboxide contents (Ti4+ 54.8%) are easy to form anatase phase by annealing

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

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