scholarly journals The Diversity and Nitrogen Metabolism of Culturable Nitrate-Utilizing Bacteria Within the Oxygen Minimum Zone of the Changjiang (Yangtze River) Estuary

2021 ◽  
Vol 8 ◽  
Author(s):  
Wenxuan He ◽  
Sizhen Liu ◽  
Zhichen Jiang ◽  
Jinshui Zheng ◽  
Xuegang Li ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Microbial Diversity ◽  
Nitrogen Metabolism ◽  
Nitrogen Cycle ◽  
Nitrate Reduction ◽  
Yangtze River ◽  
River Estuary ◽  
Yangtze River Estuary ◽  
Minimum Zone ◽  
Oxygen Minimum

The nitrogen cycle is an indispensable part of the biogeochemical cycle, and the reactions that occur in the ocean oxygen minimum zone (OMZ) mediate much of the loss of nitrogen from oceans worldwide. Here, nitrate-utilizing bacteria were isolated from the water column at 17 stations within the OMZ of the Changjiang (Yangtze River) Estuary using selective media and a culture-dependent method. The microbial diversity, nitrogen metabolism and nitrate reduction test of culturable heterotrophic bacteria were examined. A total of 164 isolates were obtained; they were mostly affiliated with Proteobacteria (81.1%), Actinobacteria (5.5%), Bacteroidetes (12.3%), and Firmicutes (0.6%). Pseudomonas aeruginosa, Sphingobium naphthae, and Zunongwangia profunda were found at most stations. Among 24 tested representative strains, 8 were positive for nitrate reduction; they belonged to genera Aurantimonas, Halomonas, Marinobacter, Pseudomonas, Thalassospira, and Vibrio. Pseudomonas aeruginosa contained the genes (napAB, norBC, nirS, and nosZ) for complete denitrification and may be responsible for mediating denitrification. 66% representative isolates (16/24) contained genes for reducing nitrate to nitrite (nasA, napAB, or narGHI) and 79% representative isolates (19/24) possessed genes for converting nitrite to ammonia (nirA or nirBD), suggesting that nitrate and nitrite could act as electron acceptors to generate ammonium, subsequently being utilized as a reduced nitrogen source. This study improves our understanding of the microbial diversity within the OMZ of Changjiang Estuary and may facilitate the cultivation and exploitation of bacteria involved in the nitrogen cycle.

scholarly journals Spatial and Temporal Variability of Soil Salinity in the Yangtze River Estuary Using Electromagnetic Induction

2021 ◽  
Vol 13 (10) ◽  
pp. 1875
Author(s):  
Wenping Xie ◽  
Jingsong Yang ◽  
Rongjiang Yao ◽  
Xiangping Wang
Keyword(s):  
Electrical Conductivity ◽  
Spatial Distribution ◽  
Soil Salinity ◽  
Yangtze River ◽  
Laboratory Data ◽  
River Estuary ◽  
Yangtze River Estuary ◽  
Soil Electrical Conductivity ◽  
The Yangtze River ◽  
The Yangtze River Estuary

Soil salt-water dynamics in the Yangtze River Estuary (YRE) is complex and soil salinity is an obstacle to regional agricultural production and the ecological environment in the YRE. Runoff into the sea is reduced during the impoundment period as the result of the water-storing process of the Three Gorges Reservoir (TGR) in the upper reaches of the Yangtze River, which causes serious seawater intrusion. Soil salinity is a problem due to shallow and saline groundwater under serious seawater intrusion in the YRE. In this research, we focused on the temporal variation and spatial distribution characteristics of soil salinity in the YRE using geostatistics combined with proximally sensed information obtained by an electromagnetic induction (EM) survey method in typical years under the impoundment of the TGR. The EM survey with proximal sensing method was applied to perform soil salinity survey in field in the Yangtze River Estuary, allowing quick determination and quantitative assessment of spatial and temporal variation of soil salinity from 2006 to 2017. We developed regional soil salinity survey and mapping by coupling limited laboratory data with proximal sensed data obtained from EM. We interpreted the soil electrical conductivity by constructing a linear model between the apparent electrical conductivity data measured by an EM 38 device and the soil electrical conductivity (EC) of soil samples measured in laboratory. Then, soil electrical conductivity was converted to soil salt content (soil salinity g kg−1) through established linear regression model based on the laboratory data of soil salinity and soil EC. Semivariograms of regional soil salinity in the survey years were fitted and ordinary kriging interpolation was applied in interpolation and mapping of regional soil salinity. The cross-validation results showed that the prediction results were acceptable. The soil salinity distribution under different survey years was presented and the area of salt affected soil was calculated using geostatistics method. The results of spatial distribution of soil salinity showed that soil salinity near the riverbanks and coastlines was higher than that of inland. The spatial distribution of groundwater depth and salinity revealed that shallow groundwater and high groundwater salinity influenced the spatial distribution characteristics of soil salinity. Under long-term impoundment of the Three Gorges Reservoir, the variation of soil salinity in different hydrological years was analyzed. Results showed that the area affected by soil salinity gradually increased in different hydrological year types under the impoundment of the TGR.

scholarly journals Numerical Study on the Expansion and Variation of Changjiang Diluted Water in Summer and Autumn

2021 ◽  
Vol 9 (3) ◽  
pp. 317
Author(s):  
Wanli Hou ◽  
Menglin Ba ◽  
Jie Bai ◽  
Jianghua Yu
Keyword(s):  
Yangtze River ◽  
Sea Water ◽  
Numerical Study ◽  
River Estuary ◽  
Ocean Model ◽  
Theoretical Research ◽  
Yangtze River Estuary ◽  
Hydrodynamic Characteristics ◽  
Changjiang Diluted Water ◽  
Transportation Route

In view of the expansion and directional change mechanisms of Yangtze River water diluted with sea water in the shelf region (also known as Changjiang diluted water [CDW]) during summer and autumn, a three-dimensional hydrodynamic model of the Yangtze River Estuary (YRE) and its adjacent waters was established based on the Finite Volume Community Ocean Model (FVCOM). Compared with the measured data, the model accurately simulates the hydrodynamic characteristics of the YRE. On that basis, the influence of the expansion patterns of the CDW in both summer and autumn was studied. It was found that, in 2019, the CDW expanded to the northeast in the summer and to the southeast in the autumn, and that the route of the CDW is mainly controlled by the wind, not the runoff. Current seasonal winds also change the transportation route of the CDW by affecting its hydrodynamic field. Typhoons are frequent in both summer and autumn, causing abnormalities in both the transportation route and expansion of the CDW. During a typhoon, a large amount of the CDW is transported in a continuous and abnormal manner, accelerating the path turning of the CDW. This paper enhances the existing theoretical research of the CDW and provides a reference with respect to the expansion of diluted water all over the world.

Biomass size spectra of net plankton in the adjacent area near the Yangtze River Estuary in spring

2008 ◽  
Vol 28 (3) ◽  
pp. 1174-1182 ◽  
Author(s):  
Zuo Tao ◽  
Wang Jun ◽  
Jin Xianshi ◽  
Li Zhongyi ◽  
Tang Qisheng
Keyword(s):  
Yangtze River ◽  
River Estuary ◽  
Yangtze River Estuary ◽  
Adjacent Area ◽  
The Yangtze River ◽  
Size Spectra ◽  
The Yangtze River Estuary
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