Fractionation of metals in soil for strawberry cultivation: Effect on metal migration in food chain and application in risk assessment.

Although trace metals in strawberry production system have attracted growing attention, little is known about metal fractionation in soil for strawberry cultivation. We hypothesized that the metal fractions in soil influenced by strawberry production had significant effect on food chain transport of metals and their risk in soil. Here, samples of strawberries and soil were gathered in the Yangtze River Delta, China to verify the hypothesis. Results showed that the acid-soluble Cr, Cd, and Ni in soil for strawberry cultivation were 21.5%-88.3% higher than those in open field soil, which enhanced uptake and bioaccessible levels of these metals in strawberries. Overall, the ecological, mobility, and health risks of Pb, Zn, Ni, and Cu in soil were at a low level. However, the ecological risk of bioavailable Cd, mobility risk of Cd, and cancer risk of bioavailable Cr in over 70% of the soil samples were at moderate, high, and acceptable levels, respectively. Since the increased acid-soluble Cr and Ni in soil were related to soil acidification induced by strawberry production, nitrogen fertilizer application should be optimized to prevent soil acidification and reduce transfer of Cr and Ni. Additionally, as Cd and organic matter accumulated in soil, the acid-soluble Cd and the ecological and mobility risks of Cd in soil were enhanced. To decrease transfer and risk of Cd in soil, organic fertilizer application should be optimized to mitigate Cd accumulation, alter organic matter composition, and subsequently promote the transformation of bioavailable Cd into residual Cd in soil.

Quantitative assessment methodology framework of the impact of global climate change on the aquatic habitat of warm-water fish species in rivers.

Global climate change (GCC), with global warming as the main characteristic, has become a global issue widely concerned by people. GCC impacts the hydrological regime at the watershed scale and affects the hydrodynamic force and the habitat conditions of freshwater ecosystems at the river scale. The impact of GCC on water resources and the water cycle is a research hotspot. However, there are few studies on water environment ecology related to hydrology and the influence of changes in discharge and water temperature on warm-water fish habitats. This study proposes a quantitative assessment methodology framework for predicting and analyzing the impact of GCC on the warm-water fish habitat. This system integrates GCC, downscaling, hydrological, hydrodynamic, water temperature and habitat models and was applied to the middle and lower reaches of the Hanjiang River (MLHR), where there are four major Chinese carps resource reduction problems. The results showed that the calibration and validation of the statistical downscaling model (SDSM) and the hydrological, hydrodynamic, and water temperature models were carried out using the observed meteorological factors, discharge, water level, flow velocity and water temperature data. The change rule of the simulated value was in good agreement with the observed value, and the models and methods used in the quantitative assessment methodology framework were applicable and accurate. The rise of water temperature caused by GCC will ease the problem of low-temperature water in the MLHR, and the weighted usable area (WUA) for spawning of the four major Chinese carps will appear in advance. Meanwhile, the increase in future annual discharge will play a positive role in WUA. In general, the rise in confluence discharge and water temperature caused by GCC will increase WUA, which is beneficial to the spawning ground of four major Chinese carps.

Determining the position of a fish passage facility entrance based on endemic fish swimming abilities and flow field.

Hydropower development can significantly mitigate climate change and reduce carbon emissions, but it can also have substantial negative impacts on river environments and fish biodiversity. Fish passage facilities are built to ensure sustainable hydropower development and the biodiversity of fish populations. The locations of the entrances to these facilities play a key role in their efficiency. This study presents a reliable approach that combines the swimming ability of fish and a numerical flow field simulation to determine the optimal location for a fish passage facility entrance. In this study, we used the Gujun Reservoir upstream of the Yangtze River as a case study. A field experiment was conducted, and the swimming abilities of eight endemic fish species in the upstream region of the Yangtze River were measured. Among the tested species, the fastest induced swimming speed (0.14 m/s) was achieved by Glyptothorax sinense, while the slowest critical swimming speed (0.30 m/s) was observed for Paracobitis potanini. We propose that the velocity near the fish passage facility entrance should be higher than the maximum induced swimming speed and lower than the minimum critical swimming speed, making the suitable range between 0.14 and 0.30 m/s. On this basis, velocity fields 500 m downstream of the dam of the Gujun Reservoir under 4 operating conditions with discharge flows of 5.7 m3/s, 23.3 m3/s, 32.5 m3/s, and 41.1 m3/s were calculated. The results showed that the flow field variation downstream of the dam was between 0.1 and 0.9 m/s. After comparing the suitable areas for the target species, the left bank at location 2 was recommended as the optimal location for the fish passage facility entrance in the Gujun Reservoir.

River habitat assessment and restoration in high dam flood discharge systems with total dissolved gas supersaturation.

The success of river habitat restoration relies on accurate assessment proxies. However, determining how to quantitatively assess the impact of multiple stressors during flood discharge from high dams in riverine ecosystems and where and how to implement more reliable recovery interventions remain challenges. Here, we developed a bottom-up mechanistic framework for assessing the effects of total dissolved gas supersaturation (TDGS) and hydrodynamics on fish habitat quality and applied it to the downstream river reach of the Xiangjiaba Dam in Southwest China. The results showed that the available habitat area of river sturgeon was the smallest, while Chinese sucker had the largest available habitat area among the three target species under all discharge scenarios. Although the TDGS levels were evenly mixed laterally, the habitat suitability index indicated that the suitable habitats were primarily within both sides of the river reach under all scenarios, which is contrary to findings based on the traditional TDGS risk assessment model. The traditional TDGS risk assessment model overestimates the impact of dams on habitats. This divergence reflected the sensitivity of the habitat assessment to fish habitat preferences, fish tolerance to TDGS and the biological response of fish under TDGS. Additionally, the priority areas for restoration can be identified by habitat suitability index with lower values. We simulated twenty-four schemes and found that interventions such as stone groups, ecological spur dike, water-retaining weir and river dredging can enhance habitat suitability for fish species under multiple stressors, providing novel insights into where and how to mitigate the impact of TDGS. Our findings offer a transferable framework for the quantitative evaluation of fish habitat and implementation of restoration management during dam flood discharge periods, thus providing a new perspective for biodiversity conservation and habitat restoration in dam-regulated rivers with TDGS around the world.

Influence of socioeconomic development on river water quality: a case study of two river basins in China.

Social and economic development processes require large amounts of natural resources and in some cases seriously deteriorate river water quality. Since the reform and expansion era began, China has vigorously pursued socioeconomic development but neglected environmental protection. However, in recent years, improvements in environmental awareness and the implementation of environmental protection measures have led to a balanced relationship between economic development and the environment. In this study, the Yangtze River Basin and the Yellow River Basin were selected as research areas. We used a combination of canonical correlation analysis (CCA) and a distance-based influence assessment method to quantitatively assess the influence of socioeconomic development on river water quality. The results revealed a strong correlation between socioeconomic development and river water quality. The degree of influence of socioeconomic development on water quality varied not only temporally but also spatially due to differences in socioeconomic development and hydrometeorology in the two basins in North and South China. The average degree of influence in the Yangtze River Basin was between 0.22 and 0.27, and that in the Yellow River Basin was between 0.2 and 0.36. Moreover, the degree of influence in the Yangtze River Basin in the wet season was greater than that in the dry season, whereas the opposite pattern was observed in the Yellow River Basin. The degree of influence in both basins gradually declined after 2011, indicating that the coupling and coordination between socioeconomic development and environmental protection have continuously improved and that the water quality has gradually improved. By analysing the influences of various socioeconomic indicators on water quality, we found that the main factors that influence water quality are per capita GDP and urbanization rate in the Yangtze River Basin and urbanization rate in the Yellow River Basin. The results provide a basis for future sustainable development in the Yangtze River Basin and the Yellow River Basin.

Linking bait and feeding opportunities to fish foraging habitat for the assessment of environmental flows and river restoration.

The survival of aquatic biota in different life history stages depends on food availability, water quantity and specific hydrological conditions, and is particularly susceptible in degraded rivers due to the development of hydropower or are sensitive to climate change. Habitats with limited food availability and restricted feeding opportunities can strongly affect the habitat carrying capacity and fish growth with consequences for spawning. Few environmental flow regime frameworks are available that closely link bait and feeding opportunities to fish foraging habitat. In addition, river restoration has been widely implemented to resolve the conflict between ecological demand and power generation benefits. Nevertheless, whether in-stream structures are still suitable for the joint operation of foraging and spawning habitats remains unclear. In this study, a framework to integrate the requirements of both spawning and foraging habitats into environmental flow regime assessments was proposed by coupling the bait supply, fish spawning and fish feeding opportunities. Here, we used the Batang Reservoir, located in the Tibetan Plateau, as an example to determine the environmental flow regimes. The environmental flow regimes during Periods I, II and III for the conservation of the life history stages of Schizothorax dolichonem were determined, which provided high-quality food and was beneficial for increasing the probability of restoration success. After the implementation of measures, the ecological base flow rate decreased from 171.80 m3/s, 206.00 m3/s and 257.70 m3/s to 138.00 m3/s, 206.00 m3/s and 206.00 m3/s in Periods I, II and III, respectively. We concluded that traditional river restoration with the use of in-stream structures is still suitable for the joint operation of spawning and foraging habitats, but the design selection and placement of in-stream structures should be preoptimized. The framework proposed will help managers evaluate habitat conservation to protect degraded rivers or help develop strategies to build resilience to climate change.

Enzymatic production of HMO mimics by the sialylation of galacto-oligosaccharides.

Human milk oligosaccharides (HMOs) are a family of structurally diverse unconjugated glycans that exhibit a wide range of biological activities. In this report, we describe an efficient, Multi-Enzyme One-Pot strategy to produce HMO mimics by the sialylation of galacto-oligosaccharides (GOSs), which are often added to infant formula as an inexpensive alternative to HMOs. In this system, the sialyltransferase donor, cytidine-5'-monophospho-N-acetylneuraminic acid (CMP-Neu5Ac), was generated in situ using a CMP-sialic acid synthetase. The sialylated GOSs were obtained by one-step purification after digesting CMP using the alkaline phosphatase PhoA to cytidine and inorganic phosphate. Although the synthesized α2,3-, α2,6- and α2,3/8-sialyl-GOSs exhibit different sialylation levels and patterns, all of these mixtures can be fermented by Bifidobacterium longum subsp. infantis ATCC 15697 but not by Bifidobacterium adolescentis ATCC 15703. The sialidase NanH2, which is unique to the former strain, hydrolyzed all of the synthesized HMO mimics.