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Liu X, Zhang J, Wu Y, Yu Y, Sun J, Mao D, Zhang G. Intensified effect of nitrogen forms on dominant phytoplankton species succession by climate change. WATER RESEARCH 2024; 264:122214. [PMID: 39116610 DOI: 10.1016/j.watres.2024.122214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Revised: 07/04/2024] [Accepted: 08/03/2024] [Indexed: 08/10/2024]
Abstract
Nutrient proportion, light intensity, and temperature affect the succession of dominant phytoplankton species. Despite these insights, this transformation mechanism in highly turbid lakes remains a research gap, especially in response to climate change. To fill this gap, we investigated the mechanism by which multi-environmental factors influence the succession of dominant phytoplankton species in Lake Chagan. This investigation deployed the structural equation model (SEM) and the hydrodynamic-water quality-water ecology mechanism model. Results demonstrated that the dominant phytoplankton species in Lake Chagan transformed from diatom to cyanobacteria during 2012 and 2022. Notably, Microcystis was detected in 2022. SEM revealed the primary environment variables for this succession, including water temperature (Tw), nutrients (total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH4N)), and total suspended solids (TSS). Moreover, this event was not the consequence of zooplankton grazing. An integrated hydrodynamic-water quality-bloom mechanism model was built to explore the mechanism driving phytoplankton succession and its response to climate change. Nutrients determined the phytoplankton biomass and dominant species succession based on various proportions. High NH4N:NO3N ratios favored cyanobacteria and inhibited diatom under high TSS. Additionally, the biomass proportions of diatom (30.77 % vs. 22.28 %) and green (30.56 % vs. 23.30 %) decreased dramatically. In contrast, cyanobacteria abundance remarkably increased (35.78 % to 51.71 %) with the increasing NH4-N:NO3-N ratios. In addition, the proportion of non-nitrogen-fixing cyanobacteria was higher than that of the nitrogen-fixing cyanobacteria counterparts when TN:TP≥20 and NH4N:NO3N ≥ 10. Light-limitation phenotypes also experienced an increase with the rising NH4N:NO3N ratios. Notably, the cyanobacterial biomass reached 3-6 times that in the baseline scenario when the air temperature escalated by 3.0 °C until 2061 under the SSP585 scenario. We highlighted the effect of nitrogen forms on the succession of dominant phytoplankton species. Climate warming will increase nitrogen proportion, providing an insightful reference for controlling cyanobacterial blooms.
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Affiliation(s)
- Xuemei Liu
- State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Jingjie Zhang
- State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Yanfeng Wu
- State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Yexiang Yu
- State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Jingxuan Sun
- State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Dehua Mao
- State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Guangxin Zhang
- State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China.
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Ji Y, Shi W, Qin B. An indispensable role of overlying water in nitrogen removal in shallow lakes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 923:171487. [PMID: 38447717 DOI: 10.1016/j.scitotenv.2024.171487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Revised: 02/22/2024] [Accepted: 03/03/2024] [Indexed: 03/08/2024]
Abstract
The nitrogen (N) removal characteristics in water columns and sediments of shallow lakes, influenced by various factors, may exhibit spatial variations in lakes with algal-macrophyte dominance. The N removal rates in water columns and sediments of Lake Taihu were investigated. Our findings indicated that the total N removal rates in Lake Taihu followed the order of algae-dominance > macrophyte-dominance > pelagic lake (without the presence of algae and macrophytes). Correlation analysis revealed that the key environmental factors affecting denitrification and anammox in sediments of algae/macrophyte-type lakes were nitrate nitrogen (NO3--N), nitrite nitrogen (NO2--N), ammonia nitrogen (NH4+-N), and chlorophyll a (Chl-a). The linear regression demonstrated that a significant correlation between the denitrification and the anammox in sediments, with a correlation coefficient of 0.81 (p < 0.01). The contributions to N removal from the water columns and sediments in Lake Taihu were 53 % and 47 %, respectively. Denitrification predominantly drove N removal from sediments, whereas anammox dominated the N removal in water columns. Thus, N removal from the water columns is nonnegligible in shallow eutrophic lakes. This study enhances our understanding of N biogeochemical cycling dynamics in sediment-water and algae/macrophyte ecosystems across various shallow eutrophic lake regions.
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Affiliation(s)
- Yuyu Ji
- School of Hydrology, Hohai University, 1 Xikang Road, Nanjing 213022, China; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China
| | - Wenqing Shi
- School of Environmental Science Engineering, Nanjing University of Information Science Technology, 219 Ningliu Road, Nanjing 210044, China
| | - Boqiang Qin
- School of Hydrology, Hohai University, 1 Xikang Road, Nanjing 213022, China; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China; School of Geography & Ocean Science, Nanjing University, 163 Xianlin Street, Nanjing 210023, China.
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Jia Y, Hu X, Kang W, Dong X. Unveiling Microbial Nitrogen Metabolism in Rivers using a Machine Learning Approach. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:6605-6615. [PMID: 38566483 DOI: 10.1021/acs.est.3c09653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Microbial nitrogen metabolism is a complicated and key process in mediating environmental pollution and greenhouse gas emissions in rivers. However, the interactive drivers of microbial nitrogen metabolism in rivers have not been identified. Here, we analyze the microbial nitrogen metabolism patterns in 105 rivers in China driven by 26 environmental and socioeconomic factors using an interpretable causal machine learning (ICML) framework. ICML better recognizes the complex relationships between factors and microbial nitrogen metabolism than traditional linear regression models. Furthermore, tipping points and concentration windows were proposed to precisely regulate microbial nitrogen metabolism. For example, concentrations of dissolved organic carbon (DOC) below tipping points of 6.2 and 4.2 mg/L easily reduce bacterial denitrification and nitrification, respectively. The concentration windows for NO3--N (15.9-18.0 mg/L) and DOC (9.1-10.8 mg/L) enabled the highest abundance of denitrifying bacteria on a national scale. The integration of ICML models and field data clarifies the important drivers of microbial nitrogen metabolism, supporting the precise regulation of nitrogen pollution and river ecological management.
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Affiliation(s)
- Yuying Jia
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Xiangang Hu
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Weilu Kang
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Xu Dong
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
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Zhang W, Li H, Xu D, Xia T. Wetland Destruction in a Headwater River Leads to Disturbing Decline of In-stream Nitrogen Removal. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:2774-2785. [PMID: 38299516 DOI: 10.1021/acs.est.3c07404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
Wetlands have long been recognized as efficient nitrogen (N) processing systems. While widespread interest is in constructing wetlands to mitigate N pollution, there is a dearth of information about the environmental consequences following wetland dismantlement. This study elucidated the changing trajectories of water quality and N removal capacity in a headwater river that initially contained a series of constructed wetlands but later underwent wetland destruction. An estimated 17% surge in total N concentration has been reported since the wetlands' destruction. This adverse trend is primarily attributed to a weakened in-stream N removal capacity, which was reduced to a mere 25% of the levels observed when the wetlands were operational. Further analysis confirms that the presence of wetlands actively shapes desirable environmental settings for N processing. In stark contrast, wetland destruction leads to unfavorable environmental conditions, which not only restrain in-stream anaerobic metabolisms but also trigger algal proliferation and biological N fixation. Collectively, this research provides compelling evidence of the detrimental consequences associated with wetland destruction, emphasizing the need for remedial strategies to mitigate these negative effects.
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Affiliation(s)
- Wangshou Zhang
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Hengpeng Li
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Dawei Xu
- State Key Laboratory of Marine Geology, Tongji University, Shanghai 20092, China
| | - Tianyu Xia
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
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Zhang L, Bai J, Zhai Y, Zhang K, Wang Y, Tang R, Xiao R, Jorquera MA. Seasonal changes in N-cycling functional genes in sediments and their influencing factors in a typical eutrophic shallow lake, China. Front Microbiol 2024; 15:1363775. [PMID: 38374918 PMCID: PMC10876089 DOI: 10.3389/fmicb.2024.1363775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Accepted: 01/22/2024] [Indexed: 02/21/2024] Open
Abstract
N-cycling processes mediated by microorganisms are directly linked to the eutrophication of lakes and ecosystem health. Exploring the variation and influencing factors of N-cycling-related genes is of great significance for controlling the eutrophication of lakes. However, seasonal dynamics of genomic information encoding nitrogen (N) cycling in sediments of eutrophic lakes have not yet been clearly addressed. We collected sediments in the Baiyangdian (BYD) Lake in four seasons to explore the dynamic variation of N-cycling functional genes based on a shotgun metagenome sequencing approach and to reveal their key influencing factors. Our results showed that dissimilatory nitrate reduction (DNRA), assimilatory nitrate reduction (ANRA), and denitrification were the dominant N-cycling processes, and the abundance of nirS and amoC were higher than other functional genes by at least one order of magnitude. Functional genes, such as nirS, nirK and amoC, generally showed a consistent decreasing trend from the warming season (i.e., spring, summer, fall) to the cold season (i.e., winter). Furthermore, a significantly higher abundance of nitrification functional genes (e.g., amoB, amoC and hao) in spring and denitrification functional genes (e.g., nirS, norC and nosZ) in fall were observed. N-cycling processes in four seasons were influenced by different dominant environmental factors. Generally, dissolved organic carbon (DOC) or sediment organic matter (SOM), water temperature (T) and antibiotics (e.g., Norfloxacin and ofloxacin) were significantly correlated with N-cycling processes. The findings imply that sediment organic carbon and antibiotics may be potentially key factors influencing N-cycling processes in lake ecosystems, which will provide a reference for nitrogen management in eutrophic lakes.
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Affiliation(s)
- Ling Zhang
- School of Environment, Beijing Normal University, Beijing, China
- School of Chemistry and Chemical Engineering, Qinghai Normal University, Xining, China
| | - Junhong Bai
- School of Environment, Beijing Normal University, Beijing, China
| | - Yujia Zhai
- School of Environment, Beijing Normal University, Beijing, China
| | - Kegang Zhang
- Department of Environmental Engineering and Science, North China Electric Power University, Baoding, China
| | - Yaqi Wang
- School of Environment, Beijing Normal University, Beijing, China
| | - Ruoxuan Tang
- School of Environment, Beijing Normal University, Beijing, China
| | - Rong Xiao
- College of Environment & Safety Engineering, Fuzhou University, Fuzhou, China
| | - Milko A. Jorquera
- Laboratorio de Ecología Microbiana Aplicada (EMALAB), Departamento de Ciencias Químicas y Recursos Naturales, Universidad de La Frontera, Temuco, Chile
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Yin H, Yin P, Yang Z. Seasonal sediment phosphorus release across sediment-water interface and its potential role in supporting algal blooms in a large shallow eutrophic Lake (Lake Taihu, China). THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 896:165252. [PMID: 37400027 DOI: 10.1016/j.scitotenv.2023.165252] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 06/27/2023] [Accepted: 06/29/2023] [Indexed: 07/05/2023]
Abstract
Seasonal sediment internal phosphorus (P) release is known to affect annual algal blooms in eutrophic lakes. In this study, a year-long field investigation and laboratory sediment core incubation were conducted to study the relationship between sediment internal P cycling and algal growth in Lake Taihu. The results indicated that the concentrations of water total phosphorus (TP) and chlorophyll-a (Chla) correlated with seasonal temperature and were assumed to be caused by internal P release. From cold winter to warm seasons, sediment internal P (porewater P concentration and P flux) exhibits dynamic changes. Sediment porewater soluble reactive phosphorus (SRP) and its flux in the summer were approximately five times and eight times those during winter, respectively. The release of sediment mobile P in the summer decreases its concentration and can supply SRP for algal blooms. Laboratory core incubation indicated that Chla and phycocyanin concentrations in the overlying water showed similar changes to sediment porewater P and P flux when cores were incubated from low to high temperature. The results of this study indicated that warmer conditions could increase the sediment porewater P concentration and sediment P flux into the bottom waters and consequently enhance sediment P availability to algae. This study provides new insights into the relationship between internal sediment P cycling and algal blooms in Lake Taihu.
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Affiliation(s)
- Hongbin Yin
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, People's Republic of China; University of Chinese Academy of Sciences, Nanjing, Nanjing 211135, China.
| | - Peng Yin
- Water Resource Service Center of Jiangsu Province, Nanjing 210029, China
| | - Zhen Yang
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, People's Republic of China
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Jiang X, Liu C, Cai J, Hu Y, Shao K, Tang X, Gong Y, Yao X, Xu Q, Gao G. Relationships between environmental factors and N-cycling microbes reveal the indirect effect of further eutrophication on denitrification and DNRA in shallow lakes. WATER RESEARCH 2023; 245:120572. [PMID: 37688860 DOI: 10.1016/j.watres.2023.120572] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 08/23/2023] [Accepted: 09/01/2023] [Indexed: 09/11/2023]
Abstract
Traditional views indicate that eutrophication and subsequent algal blooms favor denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in lake ecosystems. However, lakes tend to show an increasing propensity for inorganic nitrogen (N) limitation as they become more eutrophic. Thus, the influence of further eutrophication on denitrification and DNRA in eutrophic lakes are unclear due to the uncertainty of N availability. To fill this gap, we investigated the genes abundance (AOA, AOB, nirS, nirK and nrfA) and the composition of N-cycling microbes through quantitative PCR and 16S rRNA sequencing analysis, respectively, in 15 shallow eutrophic lakes of the Yangtze-Huaihe River basin, China. The results indicated that denitrification and DNRA rates could be modulated mainly by their functional gene abundances (nirS, nirK and nrfA), followed by the environmental factors (sediment total organic carbon and nitrogen). Denitrification rates significantly increased from slightly to highly eutrophic lakes, but DNRA rates were not. An explanation is that nitrification provided ample nitrate for denitrification, and this cooperative interaction was indicated by the positive correlation of their gene abundances. In addition, Pseudomonas and Anaeromyxobacter was the dominant genus mediated denitrification and DNRA, showing the potential to perform facultative anaerobic and strict anaerobic nitrate reduction, respectively. High level of dissolved oxygen might favor the facultatively aerobic denitrifiers over the obligately anaerobic fermentative DNRA bacteria in these shallow lakes. Chlorophyll a had a weak but positive effect on the gene abundances for nitrification (AOA and AOB). Further eutrophication had an indirect effect on denitrification and DNRA rates through modulating the genes abundances of N-cycling microbes.
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Affiliation(s)
- Xingyu Jiang
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Changqing Liu
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jian Cai
- Xiangyang Polytechnic, Xiangyang 441050, China
| | - Yang Hu
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Keqiang Shao
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Xiangming Tang
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Yi Gong
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Xiaolong Yao
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Qiujin Xu
- Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Guang Gao
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
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Zhao Z, Zhang M, Chen Y, Ti C, Tian J, He X, Yu K, Zhu W, Yan X, Wang Y. Traceability of nitrate polluted hotspots in plain river networks of the Yangtze River delta by nitrogen and oxygen isotopes coupling bayesian model. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 315:120438. [PMID: 36265730 DOI: 10.1016/j.envpol.2022.120438] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/05/2022] [Accepted: 10/12/2022] [Indexed: 05/25/2023]
Abstract
The adverse effects of increased nitrate (NO3-) pollution especially from the non-point source on the hydrosphere and anthroposphere are becoming more prominent. The non-point-derived NO3- in the rivers supplying the upstream threatens the aquatic ecosystem of Taihu Lake. Here, dual-stable isotopes (δ15N and δ18O) of NO3- were applied to the Bayesian model (SIAR) for quantitative source identification of reactive nitrogen (Nr) in a mixed agricultural and urban region along the complex river network of the Yangze River delta. The results showed that the NO3- concentrations in the rivers ranged from 1.09 to 4.44 mg L-1 and decreased from the highly urbanized areas to the lakeside rural areas. The specific isotopic characteristics of four sources (atmospheric deposition, AD; chemical fertilizer, CF; manure and sewage, MS; and soil leachate, SL) by the SIAR isotope model indicated that the MS source made the greatest contribution (46.56%) to the total NO3- load, followed by SL (27.86%), CF (23.77%), and AD (1.81%). The highly urbanized areas and the hybrid areas, which contained a mix of industrialized, populated, and agricultural areas, were identified as hotspot areas with heavy Nr pollution, responsible for spatial patterns of δ15N-NO3- and δ18O-NO3-. These hotspot areas were characterized by a less well-developed sewage pipeline system with high Nr emissions from cash crops. The changes in wastewater treatment level, the agricultural production structure, and meteorological changes were the main factors of spatial variation of Nr concentration and source in the upstream Taihu Lake Basin. The variation in Nr concentration across Taihu Lake would respond to these anthropogenic-driven Nr loads. These findings suggest that MS was the predominant source had the strongest effect on the overall riverine NO3- source which was the primary problem that needed to be solved.
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Affiliation(s)
- Zihan Zhao
- School of Geography, Nanjing Normal University, Nanjing, 210023, China
| | - Mingli Zhang
- School of Geography, Nanjing Normal University, Nanjing, 210023, China
| | - Yan Chen
- School of Geography, Nanjing Normal University, Nanjing, 210023, China
| | - Chaopu Ti
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Jiaming Tian
- School of Geography, Nanjing Normal University, Nanjing, 210023, China
| | - Xinghua He
- School of Geography, Nanjing Normal University, Nanjing, 210023, China
| | - Kangkang Yu
- School of Geography, Nanjing Normal University, Nanjing, 210023, China
| | - Wangyue Zhu
- School of Geography, Nanjing Normal University, Nanjing, 210023, China
| | - Xiaoyuan Yan
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Yanhua Wang
- School of Geography, Nanjing Normal University, Nanjing, 210023, China; Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, 210023, China; Key Laboratory of Virtual Geographic Environment, Ministry of Education, Nanjing Normal University, Nanjing, 210023, China.
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Zhang W, Li H, Cao H. Strong variability in nitrogen (N) removal rates in typical agricultural pond from hilly catchment: Evidence from diel and monthly dissolved N 2 measurement. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 314:120196. [PMID: 36126768 DOI: 10.1016/j.envpol.2022.120196] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/23/2022] [Accepted: 09/13/2022] [Indexed: 06/15/2023]
Abstract
Ponds, depressional submerged landscapes that can store and process nitrogen (N)-enriched runoff from surrounding uplands, are recognized as biogeochemical hotspots for N removal. Despite their strong potential for N removal, information is limited concerning the specifics of their changing nature. Here, we investigated the dynamics of N removal rate in a typical agricultural pond from a hilly catchment, by unraveling the monthly and diel patterns of N2 concentrations and fluxes. Our observations showed that the N pollution in the pond was severe. Its averaged total N level reached 3.6 mg L-1, of which ∼72% consisted of NO3-N. Meanwhile, the water samples were supersaturated with N2, demonstrating N removal occurring in the pond. Further estimates of net N2 fluxes indicated that N removal rates exhibited obvious day-and-night and monthly differences. On the diel scale, N removal rates exhibited a distinct diurnal cycle, with nocturnal rates around 20% higher than during the day. Such a diel pattern can be mainly explained by the fluctuation in DO levels, showing that at nighttime when photosynthesis is absent, low DO environments are conducive to N removal. On a monthly scale, the monthly rates ranged from 0.02 to 0.49 mmol N2 m-2 h-1 (mean: 0.23 mmol N2 m-2 h-1), with generally higher removal rates in the warmer and concurrently rainy months (June-September). N levels in the pond were the corresponding primary explanatory variables. Assembled data from both monthly and hourly scales provided a more complete picture of the changing nature of N removal in ponds. Future work should carefully consider the effects of altered environmental conditions triggered by hydrological events to better reveal the control mechanisms behind the time-immediate N removal from lowland ponds.
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Affiliation(s)
- Wangshou Zhang
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
| | - Hengpeng Li
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
| | - Heng Cao
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China
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Liu X, Li Y, Shen R, Zhang M, Chen F. Reducing nutrient increases diatom biomass in a subtropical eutrophic lake, China-Do the ammonium concentration and nitrate to ammonium ratio play a role? WATER RESEARCH 2022; 218:118493. [PMID: 35489153 DOI: 10.1016/j.watres.2022.118493] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 04/19/2022] [Accepted: 04/20/2022] [Indexed: 06/14/2023]
Abstract
Response of aquatic organisms to eutrophication have been well reported, while less studies are available for the recovery of eutrophic lakes following a reduction in the external loading, especially for systems where nitrogen is reduced but the phosphorus concentration is maintained high due to internal loading. Diatoms are nitrate (NO3-N) opportunists but can also use ammonium (NH4-N). They may, therefore, be more sensitive to nitrogen reduction than other algae that typically prefer NH4-N. We document the variations of nutrients and diatoms in subtropical, eutrophic Lake Taihu over 28 yr during which a reduction of the external loading resulted from lake management. According to the results of change point analysis, data on environmental variables were divided into two periods (P1: 1992-2006; P2: 2007-2019) with two different seasons (WS: Winter-Spring; SA: Summer-Autumn), respectively. Compared with P1-WS, the concentration of NH4-N decreased significantly whereas NO3-N showed no significant change in P2-WS. In contrast, NH4-N concentrations were low and showed no significant changes in P1-SA and P2-SA and NO3-N decreased significantly in the latter period. Accordingly, NO3-N: NH4-N mass ratios in P1-SA and P2-WS were all significantly higher than those in P2-SA and P1-WS, respectively. The biomass of WS diatom increased significantly and the timing of the peak biomass shifted from P1-SA to P2-WS since 2007. The SEM analysis showed that NO3-N was retained as a statistically significant predictor for diatom biomass in P1-SA and significant effects of windspeed, zooplankton and NH4-N on diatom biomass in P2-WS. Windspeed and zooplankton have further changed the biomass of diatoms in the case of declining inorganic nitrogen. We conclude that the magnitude of vernal suppression or stimulation of diatom assemblages has increased, concomitant with the variations of NH4-N and NO3-N: NH4-N mass ratios. Diatoms response to NH4-N or NO3-N is apparently changing in response to water temperature in this eutrophic shallow lake. Thus, parallel reductions in external nitrogen loading, along with variations in dominant inorganic nitrogen, will stimulate the growth of diatom and therefore increase the total biomass of phytoplankton in still high internal phosphorus loading, which is should be regarded as a good sign of restoration measures.
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Affiliation(s)
- Xia Liu
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China.
| | - Yun Li
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China
| | - Ruijie Shen
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China
| | - Min Zhang
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China
| | - Feizhou Chen
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China; Sino-Danish Centre for Education and Research (SDC), University of Chinese Academy of Sciences, Beijing 100190, P. R. China.
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