Watershed Ecology and the Environment最新文献

Sulfate-reducing bacteria (SRB), a diverse taxonomic group of anaerobic microorganisms that oxidize sulfur compounds as terminal electron acceptors, drive the key biogeochemical process of sulfate reduction. However, little is known about the diversity of SRB in tropical coastal habitats. Thus, the goal of this study is to explore and compare the community diversity of the Ashtamudi and Vembanad estuaries and evaluate the sedimentary sulfate reduction rate. The microbiome profiling of SRB was carried out using Next Generation Sequencing (NGS) techniques (Illumina sequencing) based on gene amplification of the dissimilatory sulfate reductase (dsr) enzyme to confirm the diversity and dominant taxa of SRB. The diversity of SRB represented by the Shannon alpha diversity index of the Ashtamudi estuary (6.55) was two-fold that of the Vembanad estuary. In the Vembanad estuary, the marine zone (4.09) harboured more diversity than the freshwater zone (1.825). Higher diversity and lower abundant taxa in the Ashtamudi estuary pointed out the presence of a rare biosphere that has not yet been studied. It was interesting to note that both estuaries have the same SRB phylum diversity. At the level of species, however, there was a noticeable difference. This differential diversity of SRB has an apparent influence on methane production during the breakdown of organic matter in addition to sulfate reduction. Several species of SRB have an important role in the biodegradation of persistent pollutants and the removal of heavy metals.

Zinc oxide/activated carbon from Thapsia transtagana stems (ZnO/ACTTS) composite demonstrated good photocatalytic properties for removing methyl orange (MO) dye from aqueous solution. This study utilized the chemical activation method using phosphoric acid to prepare activated carbon, which was then used to synthesize the ZnO/ACTTS composites by the hydrothermal technique at different percentages of the amount of ZnO (15, 30, 50 and 75 %). XRD, FTIR, and SEM-EDX were used to characterize the produced composite materials. The photocatalytic degradation of the catalysts was investigated for the degradation of MO dye from aqueous solution. The effects of zinc oxide content, pH of solution, and catalyst dosage were studied. Experimental results indicate that the ZnO/ACTTS (75 %) composite with exhibited good activity under acid pH conditions with an optimal catalyst dosage of 0.5 g/L. Photodegradation kinetics followed a pseudo-second order kinetics. ZnO/ACTTS composite will be a catalyst to degrade a wide range of dyes from the textile industry in the aquatic medium.

Microplastics (MPs) have been identified as emerging contaminants and have received global attention because they pose a severe threat to wildlife and the human food chain. In recent years, many studies related to the sources, distribution, and effects of MPs in marine, terrestrial, and wastewater environmental compartments have been reported, whereas a comprehensive overview of the presence and characteristics of MPs in unique coastal wetland ecosystems is still lacking. Therefore, this review summarizes the accumulation and sources of MPs in coastal wetlands, as well as their effects on these ecosystems, based on environmental monitoring and laboratory results published in the literature. First, the accumulation of MPs in coastal wetlands is briefly reviewed. Second, the sources of MPs in coastal wetlands are discussed. Third, the ecological effects of MPs on coastal wetlands are summarized. Finally, this review presents gaps in the MPs research and provides an outlook for future research in this field.

Due to the dual impacts of anthropogenic disturbances and climate change, tidal hydrodynamics of estuaries have been intensively investigated for their potential to increase flood risk and devastate coastal habitats and human communities. Climate change leads to rises in sea levels, which can amplify regional tides and increase tidal ranges. This study takes the estuarine area of the Pearl River (PRE), one of the fastest-developed estuaries in China, as an example to explore the effects of land cover changes and sea level rise on tidal dynamics. Annual mean tidal levels were collected at 26 major hydrological stations from five major rivers/waterways. To better understand the temporal changes in tidal levels, we analyzed the trends and periodic patterns through linear regression and Complex Morlet wavelet analyses. For the main Pearl River outlet, where conversion of agricultural land to urban use had been primarily taking place, the tidal level changes were significantly affected by increased built-up areas and decreased cultivated land areas. On the other hand, in the middle to upper reaches of the Xi River and Shunde-Hengmen Waterway, we observed decreased tidal levels with decreases in the agricultural lands. No significant correlations were found between annual mean tidal levels and land cover changes downstream of the main rivers. Instead, the tidal level changes at locations close to the coastline were more related to sea level rise, with an average of 0.002 m per year increase. This study highlighted the importance of human activity and sea level rise impacts on tidal dynamics. A systematic understanding of the tidal changes in the estuary is expected to help enhance mechanisms of estuarine hydrology, which could serve as the basis for improving the management and practice of coastal regions in coping with climate change and estuary protection.

Net ecosystem productivity (NEP) is an important indicator of the capacity of terrestrial ecosystems to absorb carbon. For the purpose of developing adaptation and mitigation strategies, it is essential to investigate the effect of climatic changes and anthropogenic activities on NEP. This study analyzed the spatiotemporal properties of NEP in the Yangtze River and Yellow River Source Region (SRYY) using remote sensing images, climate variable data, and land use data. Then it was examined at how climatic change affected carbon sinks and sources and how changes in land use affected carbon storage. According to the results, the SRYY contributed a carbon sink worth 35.26 Tg C annually from 2001 to 2019 (1 Tg = 10¹² g). Influenced by climate, soil and vegetation, NEP displayed regional differences in space. The spatial distribution of NEP gradually increased from Northwest to Southeast. In recent twenty years, the NEP of SRYY slightly increased with a rate of 3.24 Tg C per decade. The NEP with an increasing trend accounted for 78.9% of the whole study area, which were widely distributed and especially significant in the west, such as Tuotuo River Basin. The correlation analysis between NEP and climate variables suggested that temperature was the dominant control of NEP in the SRYY. About 54.4% of the NEP variance across the entire SRYY was contributed by temperature. However, there was no significant linear relationship between NEP and annual precipitation. In recent two decades, built-up land expansion and ecological degradation reduced carbon sink by 28.61 Gg C (1 Gg = 10⁹ g) and 1.94 Tg C, respectively. Grassland degradation caused by rodent infestation and grazing was the main factor of carbon sink reduction in some areas. The restoration of vegetation and wetland areas resulted in a 0.75 Tg C increase in the carbon sink. It might be benefited from warmer climate condition and ecological protection measures.

The urbanization in Beijing intensified the fragmentation of ecosystems, especially for the forests and wetlands. Wetlands provide multiple ecological services (e.g., a food source, climate regulation). Thus, wetland protection is part of the foundation for sustainable economic and social development for Beijing. This study summarizes the experience of well-developed cities in wetland protection and sustainable development and subsequently analyzes the current issues of Beijing’s wetlands. The results showed that a limited resource space, high human stress, and lack of scientifically based polices are the main obstacles. Therefore, we recommend the following: (1) support the utilization of rainwater and reclaimed water and optimize the coordinated utilization of water resources, (2) strengthen the ecological protection and restoration efforts to realize the ecological protection system of water–city integration, (3) build a forest water complex ecosystem in metropolises to create a livable environment with forest and water, and (4) conduct scientific and technological research on the optimal total amount of wetlands and develop wetland technologies.

The changing dynamics of river ecosystems from aquatic to terrestrial in the Southwestern areas of Bangladesh have been widely observed in recent years. Nevertheless, there has been no consensus on whether the changes are caused by human activities or by natural processes. For a better understanding of the cause, this study was conducted based on a field survey through a pre-tested structured questionnaire measuring the river water quality. The water quality of the river was assessed to know how much the existing river water was affecting its aquatic ecosystem or not. People’s perception was also investigated to assess the factors mostly responsible for changing the river ecosystem. It was found that the most responsible factors are human activities. Among them, the construction of cross embankments over and along the Bhairab River was the most (22%) responsible factor for changing the river ecosystem. The 2nd and 3rd most responsible factors were bridge construction (18%) and illegal encroachment (18%). Other reasons for changing the ecosystem of the river were the diversion (16%), cultivation of the riverside land (12%), the introduction of exotic species (8%), and disposal of wastes and industrial effluents into the river (6%), respectively. Besides, it is also believed that the construction of Farakka Barrage on the River Ganges (the mother of the Bhairab River) is also responsible for changing the aquatic ecosystem into a terrestrial ecosystem.

The Pearl River basin (PRB) is an important producing area and the gene pool of wild resources of Four Major Chinese carps (FMCC). However human activities and climate changes causes the area shrink of the river network in PRB, the pollution aggregation, the serious habitat destroy of aquatic organisms, and the threat of biological resources and their living environment. Based on the accurate location and distribution data of FMCC from the literature and the field survey report of 2015–2016, this study used the MaxEnt model to predict the hot spot distribution area of FMCC in PRB. The simulation results show that the distribution of FMCC in the PRB gradually increases from the upper reaches to the middle and lower reaches. According to the MaxEnt model, the hot spots of FMCC in the PRB are mainly distributed in the south reaches and the lower reaches of the southeast. The model simulation also demonstrates that the hottest spots for the distribution of FMCC species in the PRB are the Yujiang basin, the Qianjiang basin and the lower reaches of the Xijiang basin. This study can provide the scientific guidance for the protection and the restoration of FMCC species in the PRB.

Environmental factors such as climate change and human activities are the basic driving forces that affect the growth and distribution of vegetation. Based on the MODIS-EVI data from 2000 to 2019, this paper analyzed the interannual changes of vegetation activity in the upper reaches of the Yangtze River (UYR), and examined their responses to climatic factors (effective precipitation, accumulative temperature and solar radiation) and anthropogenic factors (urbanization, afforestation). The results showed an increasing trend in EVI over the 20-year period, with an increasing rate of 0.021/10a. Contribution amount of effective precipitation, accumulative temperature, solar radiation and anthropogenic factors to EVI inter-annual variations in the UYR were 0.004/10a, 0.009/10a, 0.001/10a and 0.007/10a, respectively. Contribution rate of climate change and anthropogenic factors accounted for 67.8% and 32.2% of the total EVI changes respectively. In areas with significant changes in EVI, influence of anthropogenic factors is generally greater than that of climatic factors, especially in Chengdu-Chongqing urban agglomeration, Wujiang River Basin and the middle and lower reaches of the Jinsha River. In alpine regions such as the source region of the Yangtze River, significant changes in EVI were dominated by climatic factors.

The livestock resources of Bangladesh are under tremendous strain due to several natural and anthropogenic causes. Especially in the Northwestern region of Bangladesh, these resources are more vulnerable to deterioration resulting from human actions, a lack of environmental and rangeland legislation, climate change, drought, poor management, and inadequate disaster mitigation plans. GIS based multicriteria decision analysis (MCDA) and remote sensing techniques have been used in this research to locate ideal land for sheep, goats, buffalo and cow production. In this study, the suitability analysis for livestock production has been considered in eight thematic layers: slope, land use & land cover (LULC), soil types, rainfall, water accessibility, road distance, relative humidity, and average temperature. Besides, this research had been used geospatial tools for combining these eight geographical layers, when analytical hierarchy process, a MCDA approach helped to measure the weight of each criterion. The final map that is perfect for raising cattle has been divided into four categories, such as low, medium, high and excellent. Each of these rangeland suitability groups has portions in the Northwestern region of Bangladesh that fall into the following percentages: 11.14%, 26.07%, 35.27%, and 27.53%. This research also depicts that the western part of the study region, which includes Thakurgaon, Panchagar, Dinajpur, Naogaon, Joypurhat and Bogra has a low suitability index for livestock production while the eastern region, which includes Kurigram, Nilphamari, Pabna, Lalmonirhat, Gaibandha, Rangpur and Sirajganj contributes to an excellent zone. The outcome of this study will be useful to identify the best places for livestock production in the Northwestern part of Bangladesh. Finally, this research may additionally assist government officials in creating environmental and rangeland strategies for the livestock population in the study area.