ABSTRACT
Fish, as top predators in aquatic ecosystems, play an important role in maintaining the structure and functioning of these ecosystems, making their diversity a topic of great interest. This study focused on the Yangtze River Basin to investigate the fish community structure and diversity using environmental DNA (eDNA) technology. The results showed that a total of 71616 fish operational taxonomic units (OTUs) and 90 fish belonging to 23 families were detected, with the Cyprinidae family being the dominant group, followed by the Cobitidae, Amblycipitidae, etc. Compared to historical traditional morphological fish surveys, the quantity of fish detected using eDNA was relatively low, but the overall distribution pattern of fish communities was generally consistent. The highest fish Shannon-Wiener diversity index in the Yangtze River Basin sites reaches 2.60 with an average value of 1.25. The fish diversity index was higher in the downstream compared to the middle and upstream regions, and there were significant differences among different sampling sites. Significant environmental factors influencing α-diversity included chlorophyll-a, chemical oxygen demand, dissolved oxygen, total nitrogen, and elevation. Non-metric multidimensional scaling (NMDS) analysis revealed significant differences in fish community composition between the upstream and middle/lower reaches of the Yangtze River, while the composition of fish communities in the middle and lower reaches was more similar. Redundancy analysis (RDA) indicated that total organic carbon (TOC) was positively correlated with fish community distribution in the upstream, while water temperature and NO3-N were negatively correlated with fish distribution in the upstream. NH3-N and CODMn were negatively correlated with fish distribution in the middle and downstream regions, indicating a relatively severe water pollution in these areas. Additionally, fish communities in the Yangtze River displayed a typical distance decay pattern.
Subject(s)
Cyprinidae , DNA, Environmental , Humans , Animals , Ecosystem , Cyprinidae/genetics , Water Pollution , Rivers , Environmental Monitoring , ChinaABSTRACT
BACKGROUND: Xylo-oligomers are a kind of high value-added products in biomass fractionation. Although there are several chemical methods to obtain xylo-oligomers from biomass, the reports about the deep eutectic solvents (DESs)-mediated co-production of xylo-oligomers and fermentable sugars and the related kinetic mechanism are limited. RESULTS: In this work, glycolic acid-based DESs were used to obtain xylo-oligomers from corncob. The highest xylo-oligomers yield of 65.9% was achieved at 120 °C for 20 min, of which the functional xylo-oligosaccharides (XOSs, DP 2-5) accounted for up to 31.8%. Meanwhile, the enzymatic digestion of cellulose and xylan in residues reached 81.0% and 95.5%, respectively. Moreover, the addition of metal inorganic salts significantly accelerated the hydrolysis of xylan and even the degradation of xylo-oligomers in DES, thus resulting in higher selectivity of xylan removal. AlCl3 showed the strongest synergistic effect with DES on accelerating the processes, while FeCl2 is best one for xylo-oligomers accumulation, affording the highest xylo-oligomers yield of 66.1% for only 10 min. Furthermore, the kinetic study indicates that the 'potential hydrolysis degree' model could well describe the xylan hydrolysis processes and glycolic acid/lactic acid (3:1) is a promising solvent for xylo-oligomers production, in particular, it worked well with FeCl2 for the excellent accumulation of xylo-oligomers. CONCLUSIONS: Glycolic acid-based deep eutectic solvents can be successfully applied in corncob fractionation with excellent xylo-oligomers and fermentable sugars yields on mild conditions, and the large amount of xylo-oligosaccharides accumulation could be achieved by specific process controlling. The strategies established here can be useful for developing high-valued products from biomass.
ABSTRACT
Watershed ecological security is strongly associated with the aquatic ecological status of the upper mountainous area. The present study aimed to assess the watershed ecological security status of the mountainous area under the PSFR (Pressure-State-Function-Response) assessment framework. An evaluation index system was established according to the watershed characteristics, which included four project hierarchical layers, i.e., aquatic ecological pressure, aquatic ecological state, ecological function, and social response, 11 component layers and 23 evaluation indexes. This index system was applied to evaluate the watershed ecological security status of the mountainous area (35 sub-watersheds) in the Taizi River Basin, Liaoning Province. Our results showed that the aquatic ecological status of the study area could be classified into three groups: insecure, general secure and secure, no very insecure and very secure status. Nine sub-watersheds were at the insecure ecological status, accounting for 25.7% of the total sub-watersheds, whereas 22 sub-watersheds were at the general secure state, representing 62.9% of the study area. In contrast, only four sub-watersheds were grouped at the secure status. Furthermore, agricultural activity was identified as the most significant factor responsible for the aquatic ecological security of mountainous area in the Taizi River Basin. Habitat degradation, including water quality deterioration and habitat loss, significantly reduced the ecological functions of the Taizi River Basin, and decreases in rare and peculiar species and biodiversity also posed a threat to the ecological integrity of the study region. Our results could be applied to diagnose the major factors affecting aquatic ecological security, and provide information for effective ecological restoration.
