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Li Y, Liu M, Wu X. Insights into biogeochemistry and hot spots distribution characteristics of redox-sensitive elements in the hyporheic zone: Transformation mechanisms and contributing factors. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 918:170587. [PMID: 38309342 DOI: 10.1016/j.scitotenv.2024.170587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 01/05/2024] [Accepted: 01/29/2024] [Indexed: 02/05/2024]
Abstract
Biogeochemical hot spots play a crucial role in the cycling and transport of redox-sensitive elements (RSEs) in the hyporheic zone (HZ). However, the transformation mechanisms of RSEs and patterns of RSEs hot spots in the HZ remain poorly understood. In this study, hydrochemistry and multi-isotope (N/C/S/O) datasets were collected to investigate the transformation mechanisms of RSEs, and explore the distribution characteristics of RSEs transformation hot spots. The results showed that spatial variability in key drivers was evident, while temporal change in RSEs concentration was not significant, except for dissolved organic carbon. Bacterial sulfate reduction (BSR) was the primary biogeochemical process for sulfate and occurred throughout the area. Ammonium enrichment was mainly caused by the mineralization of nitrogenous organic matter and anthropogenic inputs, with adsorption serving as the primary attenuation mechanism. Carbon dynamics were influenced by various biogeochemical processes, with dissolved organic carbon mainly derived from C3 plants and dissolved inorganic carbon from weathering of carbonate rocks and decomposition of organic matter. The peak contribution of dissolved organic carbon decomposition to the DIC pool was 46.44 %. The concentration thresholds for the ammonium enrichment and BSR hot spots were identified as 1.5 mg/L and 8.84 mg/L, respectively. The distribution pattern of RSEs hot spots was closely related to the hydrogeological conditions. Our findings reveal the complex evolution mechanisms and hot spots distribution characteristics of RSEs in the HZ, providing a basis for the safe utilization and protection of groundwater resources.
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Affiliation(s)
- Yu Li
- Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences (Beijing), Beijing 100083, China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China
| | - Mingzhu Liu
- Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences (Beijing), Beijing 100083, China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China.
| | - Xiong Wu
- School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China
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2
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Zhang Y, Liu J, Kang L, Gu Y, Qu L, Liu B, Sun L, Xing M, Ma Z, Sun Y. Temporal variation of mineralization rates and its influence on carbon storage over the last 50 years in Bohai Bay, China. MARINE POLLUTION BULLETIN 2023; 188:114624. [PMID: 36736251 DOI: 10.1016/j.marpolbul.2023.114624] [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: 07/17/2022] [Revised: 12/23/2022] [Accepted: 01/13/2023] [Indexed: 06/18/2023]
Abstract
Recorded information on marine sediments is affected by mineralization. In this study, we collected sediment samples from Bohai Bay, where human interference is typically high. Overall, the CO2 fluxes in the columnar sediments decreased with increasing depth. The change in constants revealed a "C-curve" in which the mineralization rate first decreased significantly (i.e., from the 2020s to the 1980s) and subsequently increased slowly (i.e., from the 1980s to 1965). This may be explained by the fact that sediments from the 1980s-2020s were markedly influenced by the sedimentation rate, whereas sediments from the 1960s-1980s were predominantly influenced by microbial action. The loss of organic carbon due to mineralization accounted for approximately 15-20 % of the initial total organic carbon; therefore, when performing an inversion of the historical environment change using information derived from organic carbon in marine sediments, the influence of mineralization on this information should be fully considered.
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Affiliation(s)
- Yan Zhang
- Tianjin Academy of Eco-Environmental Sciences, Nankai, Tianjin 300191, China
| | - Jingjing Liu
- Tianjin Academy of Eco-Environmental Sciences, Nankai, Tianjin 300191, China; Tianjin Lishen Battery Joint-stock Co., Ltd., Binhai New Area, Tianjin 300384, China
| | - Lei Kang
- Tianjin Academy of Eco-Environmental Sciences, Nankai, Tianjin 300191, China.
| | - Yingnan Gu
- Tianjin Huanke Testing Technology Co., Ltd., Nankai, Tianjin 300191, China
| | - Long Qu
- Tianjin Academy of Eco-Environmental Sciences, Nankai, Tianjin 300191, China
| | - Bao Liu
- Tianjin Academy of Eco-Environmental Sciences, Nankai, Tianjin 300191, China
| | - Lina Sun
- Tianjin Academy of Eco-Environmental Sciences, Nankai, Tianjin 300191, China
| | - Meinan Xing
- Tianjin Academy of Eco-Environmental Sciences, Nankai, Tianjin 300191, China
| | - Zhe Ma
- Tianjin Academy of Eco-Environmental Sciences, Nankai, Tianjin 300191, China
| | - Ying Sun
- Tianjin Academy of Eco-Environmental Sciences, Nankai, Tianjin 300191, China
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3
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Engel A, Kiko R, Dengler M. Organic Matter Supply and Utilization in Oxygen Minimum Zones. ANNUAL REVIEW OF MARINE SCIENCE 2022; 14:355-378. [PMID: 34460316 DOI: 10.1146/annurev-marine-041921-090849] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Organic matter (OM) plays a significant role in the formation of oxygen minimum zones (OMZs) and associated biogeochemical cycling. OM supply processes to the OMZ include physical transport, particle formation, and sinking as well as active transport by migrating zooplankton and nekton. In addition to the availability of oxygen and other electron acceptors, the remineralization rate of OM is controlled by its biochemical quality. Enhanced microbial respiration of OM can induce anoxic microzones in an otherwise oxygenated water column. Reduced OM degradation under low-oxygen conditions, on the other hand, may increase the CO2 storage time in the ocean. Understanding the interdependencies between OM and oxygen cycling is of high relevance for an ocean facing deoxygenation as a consequence of global warming. In this review, we describe OM fluxes into and cycling within two large OMZs associated with eastern boundary upwelling systems that differ greatly in the extent of oxygen loss: the highly oxygen-depleted OMZ in the tropical South Pacific and the moderately hypoxic OMZ in the tropical North Atlantic. We summarize new findings from a large German collaborative research project, Collaborative Research Center 754 (SFB 754), and identify knowledge gaps and future research priorities.
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Affiliation(s)
- Anja Engel
- GEOMAR Helmholtz Centre for Ocean Research Kiel, 24105 Kiel, Germany;
| | - Rainer Kiko
- Laboratoire d'Océanographie de Villefranche, Sorbonne Université, 06230 Villefranche-sur-Mer, France
| | - Marcus Dengler
- GEOMAR Helmholtz Centre for Ocean Research Kiel, 24105 Kiel, Germany;
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Zhang S, Zheng Q, Noll L, Hu Y, Wanek W. Environmental effects on soil microbial nitrogen use efficiency are controlled by allocation of organic nitrogen to microbial growth and regulate gross N mineralization. SOIL BIOLOGY & BIOCHEMISTRY 2019; 135:304-315. [PMID: 31579295 PMCID: PMC6774787 DOI: 10.1016/j.soilbio.2019.05.019] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Microbial nitrogen use efficiency (NUE) is the efficiency by which microbes allocate organic N acquired to biomass formation relative to the N in excess of microbial demand released through N mineralization. Microbial NUE thus is critical to estimate the capacity of soil microbes to retain N in soils and thereby affects inorganic N availability to plants and ecosystem N losses. However, how soil temperature and soil moisture/O2 affect microbial NUE to date is not clear. Therefore, two independent incubation experiments were conducted with soils from three land uses (cropland, grassland and forest) on two bedrocks (silicate and limestone). Soils were exposed to 5, 15 and 25 °C overnight at 60% water holding capacity (WHC) or acclimated to 30 and 60% WHC at 21% O2 and to 90% WHC at 1% O2 over one week at 20 °C. Microbial NUE was measured as microbial growth over microbial organic N uptake (the sum of growth N demand and gross N mineralization). Microbial NUE responded positively to temperature increases with Q10 values ranging from 1.30 ± 0.11 to 2.48 ± 0.67. This was due to exponentially increasing microbial growth rates with incubation temperature while gross N mineralization rates were relatively insensitive to temperature increases (Q10 values 0.66 ± 0.30 to 1.63 ± 0.15). Under oxic conditions (21% O2), microbial NUE as well as gross N mineralization were not stimulated by the increase in soil moisture from 30 to 60% WHC. Under suboxic conditions (90% WHC and 1% O2), microbial NUE markedly declined as microbial growth rates were strongly negatively affected due to increasing microbial energy limitation. In contrast, gross N mineralization rates increased strongly as organic N uptake became in excess of microbial growth N demand. Therefore, in the moisture/O2 experiment microbial NUE was mainly regulated by the shift in O2 status (to suboxic conditions) and less affected by increasing water availability per se. These temperature and moisture/O2 effects on microbial organic N metabolism were consistent across the soils differing in bedrock and land use. Overall it has been demonstrated that microbial NUE was controlled by microbial growth, and that NUE controlled gross N mineralization as an overflow metabolism when energy (C) became limiting or N in excess in soils. This study thereby greatly contributes to the understanding of short-term environmental responses of microbial community N metabolism and the regulation of microbial organic-inorganic N transformations in soils.
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Affiliation(s)
- Shasha Zhang
- Division of Terrestrial Ecosystem Research, Department of Microbiology and Ecosystem Science, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Qing Zheng
- Division of Terrestrial Ecosystem Research, Department of Microbiology and Ecosystem Science, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Lisa Noll
- Division of Terrestrial Ecosystem Research, Department of Microbiology and Ecosystem Science, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Yuntao Hu
- Division of Terrestrial Ecosystem Research, Department of Microbiology and Ecosystem Science, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
- Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Wolfgang Wanek
- Division of Terrestrial Ecosystem Research, Department of Microbiology and Ecosystem Science, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
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Wu M, Liu W, Liang Y. Probing size characteristics of disinfection by-products precursors during the bioavailability study of soluble microbial products using ultrafiltration fractionation. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019; 175:1-7. [PMID: 30878659 DOI: 10.1016/j.ecoenv.2019.02.077] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 02/20/2019] [Accepted: 02/25/2019] [Indexed: 06/09/2023]
Abstract
Soluble microbial products (SMPs) discharged into surface water may increase the formation of disinfection by-products (DBPs) in downstream drinking water treatment plants. In this study, ultrafiltration (UF) fractionation was used to separate SMPs into homogenous components. An aerobic microbial experiment was conducted to evaluate the bioavailability of individual molecular weight (MW) fractions of SMPs in surface water and the impact on their DBP formation, facilitating the interpretation of SMPs characterization and DBPs reactivity. For SMPs, organics with MW < 1 kDa were the primary fraction, containing the most abundant humic substances. The 30 kDa < MW < 100 kDa fraction was the lowest in SMPs but had the highest SUVA values. After biodegradation, the bioavailability of physical fractions increased with the increasing MW size. However, the SUVA value, except for MW < 1 kDa, increased in individual fraction after biodegradation. Low molecular weight SMPs fractions (MW<10 kDa) were major precursors for DBP in which trichloromethane (TCM) was the most abundant. The 10 kDa <MW < 100 kDa fractions were found to be more active in formation of chloral hydrate (CH), and MW> 100KDa had relative abundant dichloroacetonitrile (DCAN) formation. After biodegradation, TCM precursors with MW < 1 kDa were removed by approximately 20%, whereas the increase of TCM formation was observed in 1 kDa < MW < 100 kDa fraction. CH formation from 1 kDa < MW < 10 kDa increased considerably, but those from 10 kDa < MW < 30 kDa decreased after biodegradation, as a result of the biotransformation of large organic acids to small organic acids. In terms of DBP reactivity, the TCM yield for the MW < 1 kDa fraction had no significant change while the 30 kDa < MW < 100 kDa fraction exhibited the greatest increase (approximately 8 times) in TCM yield.
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Affiliation(s)
- Meirou Wu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510006, PR China.
| | - Wei Liu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510006, PR China
| | - Yongmei Liang
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510006, PR China.
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6
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Grasset C, Abril G, Mendonça R, Roland F, Sobek S. The transformation of macrophyte-derived organic matter to methane relates to plant water and nutrient contents. LIMNOLOGY AND OCEANOGRAPHY 2019; 64:1737-1749. [PMID: 31598008 PMCID: PMC6774319 DOI: 10.1002/lno.11148] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 12/21/2018] [Accepted: 01/29/2019] [Indexed: 06/10/2023]
Abstract
Macrophyte detritus is one of the main sources of organic carbon (OC) in inland waters, and it is potentially available for methane (CH4) production in anoxic bottom waters and sediments. However, the transformation of macrophyte-derived OC into CH4 has not been studied systematically, thus its extent and relationship with macrophyte characteristics remains uncertain. We performed decomposition experiments of macrophyte detritus from 10 different species at anoxic conditions, in presence and absence of a freshwater sediment, in order to relate the extent and rate of CH4 production to the detritus water content, C/N and C/P ratios. A significant fraction of the macrophyte OC was transformed to CH4 (mean = 7.9%; range = 0-15.0%) during the 59-d incubation, and the mean total C loss to CO2 and CH4 was 17.3% (range = 1.3-32.7%). The transformation efficiency of macrophyte OC to CH4 was significantly and positively related to the macrophyte water content, and negatively to its C/N and C/P ratios. The presence of sediment increased the transformation efficiency to CH4 from an average of 4.0% (without sediment) to 11.8%, possibly due to physicochemical conditions favorable for CH4 production (low redox potential, buffered pH) or because sediment particles facilitate biofilm formation. The relationship between macrophyte characteristics and CH4 production can be used by future studies to model CH4 emission in systems colonized by macrophytes. Furthermore, this study highlights that the extent to which macrophyte detritus is mixed with sediment also affects CH4 production.
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Affiliation(s)
- Charlotte Grasset
- Laboratory of Aquatic Ecology, Department of BiologyFederal University of Juiz de ForaJuiz de ForaMinas GeraisBrazil
- Limnology, Department of Ecology and GeneticsUppsala UniversityUppsalaSweden
| | - Gwenaël Abril
- Biologie des Organismes et Ecosystèmes Aquatiques (BOREA)Muséum National d'Histoire NaturelleParis cedex 05France
- Programa de GeoquímicaUniversidade Federal FluminenseNiteróiRio de JaneiroBrazil
| | - Raquel Mendonça
- Laboratory of Aquatic Ecology, Department of BiologyFederal University of Juiz de ForaJuiz de ForaMinas GeraisBrazil
- Limnology, Department of Ecology and GeneticsUppsala UniversityUppsalaSweden
| | - Fabio Roland
- Laboratory of Aquatic Ecology, Department of BiologyFederal University of Juiz de ForaJuiz de ForaMinas GeraisBrazil
| | - Sebastian Sobek
- Limnology, Department of Ecology and GeneticsUppsala UniversityUppsalaSweden
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7
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Isidorova A, Mendonça R, Sobek S. Reduced Mineralization of Terrestrial OC in Anoxic Sediment Suggests Enhanced Burial Efficiency in Reservoirs Compared to Other Depositional Environments. JOURNAL OF GEOPHYSICAL RESEARCH. BIOGEOSCIENCES 2019; 124:678-688. [PMID: 31218149 PMCID: PMC6559317 DOI: 10.1029/2018jg004823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 12/13/2018] [Accepted: 01/26/2019] [Indexed: 06/09/2023]
Abstract
Freshwater reservoirs are important sites of organic carbon (OC) burial, but the extent to which reservoir OC burial is a new anthropogenic carbon sink is currently unclear. While burial of aquatic OC (by, e.g., phytoplankton) in reservoirs may count as a new C sink, the burial of terrestrial OC in reservoirs constitutes a new C sink only if the burial is more efficient in reservoirs than in other depositional environments. We carried out incubation experiments that mimicked the environmental conditions of different depositional environments along the land-sea continuum (oxic and anoxic freshwater, oxic and anoxic seawater, oxic river bedload, and atmosphere-exposed floodplain) to investigate whether reservoirs bury OC more efficiently compared to other depositional environments. For sediment OC predominantly of terrestrial origin, OC degradation rates were significantly lower, by a factor of 2, at anoxic freshwater and saltwater conditions compared to oxic freshwater and saltwater, river, and floodplain conditions. However, the transformation of predominantly terrestrial OC to methane was one order of magnitude higher in anoxic freshwater than at other conditions. For sediment OC predominantly of aquatic origin, OC degradation rates were uniformly high at all conditions, implying equally low burial efficiency of aquatic OC (76% C loss in 57 days). Since anoxia is more common in reservoirs than in the coastal ocean, these results suggest that reservoirs are a depositional environment in which terrestrial OC is prone to become buried at higher efficiency than in the ocean but where also the terrestrial OC most efficiently is transformed to methane.
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Affiliation(s)
| | - Raquel Mendonça
- Limnology, Department of Ecology and GeneticsUppsala UniversityUppsalaSweden
- Laboratory of Aquatic Ecology, Department of BiologyFederal University of Juiz de ForaJuiz de ForaBrazil
| | - Sebastian Sobek
- Limnology, Department of Ecology and GeneticsUppsala UniversityUppsalaSweden
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Wu M, Liang Y, Peng H, Ye J, Wu J, Shi W, Liu W. Bioavailability of soluble microbial products as the autochthonous precursors of disinfection by-products in aerobic and anoxic surface water. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 649:960-968. [PMID: 30179824 DOI: 10.1016/j.scitotenv.2018.08.354] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Revised: 08/25/2018] [Accepted: 08/25/2018] [Indexed: 06/08/2023]
Abstract
Soluble microbial products (SMPs), as a major part of the effluent organic matter discharged into surface water, may affect the formation of disinfection by-products (DBP) in downstream drinking water treatment plants. In this study, excitation emission matrix fluorescence with parallel factor analysis (EEM-PARAFAC), infrared spectroscopy (IR), high performance size-exclusion chromatography (HPSEC) and 16SrRNA high-throughput sequencing were used to investigate the aerobic and anoxic bioavailability of SMPs in surface water and evaluate their influences on DBP formation upon chlorination in a subsequent drinking water plant. In this study, SMPs were utilized by enriched microbial communities such as Bacteroidetes and Proteobacteria, but the accumulation of SUVA was pronounced during the two oxygen conditions. Biodegraded SMPs had higher humic substructures and lower protein-like components. Due to the presence of SMPs, microbial community compositions were influenced during biodegradation. Moreover, DO was the main factor in biodegradation of SMPs, thus affecting a series of processes, such as microbial compositions, properties of SMPs, DBP formation and reactivity. DBP formation potential decreased after anoxic and aerobic incubations. However, SMPs after aerobic degradation had higher DBP reactivity meanwhile the opposite was found for anoxic incubation. Based on the analysis of IR and HPSEC, it was found that some new substrates or intermediates with MW (220 KDa, <1 KDa) during microbial incubation may contribute to the formation of trihalomethane (THMs), chloral hydrate (CH), dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM) in each DBP sampling episode.
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Affiliation(s)
- Meirou Wu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510006, PR China.
| | - Yongmei Liang
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510006, PR China.
| | - Huanlong Peng
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510006, PR China
| | - Jian Ye
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510006, PR China
| | - Jie Wu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510006, PR China
| | - Weiwei Shi
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510006, PR China
| | - Wei Liu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510006, PR China.
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9
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Zheng Q, Hu Y, Zhang S, Noll L, Böckle T, Richter A, Wanek W. Growth explains microbial carbon use efficiency across soils differing in land use and geology. SOIL BIOLOGY & BIOCHEMISTRY 2019; 128:45-55. [PMID: 31579288 PMCID: PMC6774786 DOI: 10.1016/j.soilbio.2018.10.006] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The ratio of carbon (C) that is invested into microbial growth to organic C taken up is known as microbial carbon use efficiency (CUE), which is influenced by environmental factors such as soil temperature and soil moisture. How microbes will physiologically react to short-term environmental changes is not well understood, primarily due to methodological restrictions. Here we report on two independent laboratory experiments to explore short-term temperature and soil moisture effects on soil microbial physiology (i.e. respiration, growth, CUE, and microbial biomass turnover): (i) a temperature experiment with 1-day pre-incubation at 5, 15 and 25 °C at 60% water holding capacity (WHC), and (ii) a soil moisture/oxygen (O2) experiment with 7-day pre-incubation at 20 °C at 30%, 60% WHC (both at 21% O2) and 90% WHC at 1% O2. Experiments were conducted with soils from arable, pasture and forest sites derived from both silicate and limestone bedrocks. We found that microbial CUE responded heterogeneously though overall positively to short-term temperature changes, and decreased significantly under high moisture level (90% WHC)/suboxic conditions due to strong decreases in microbial growth. Microbial biomass turnover time decreased dramatically with increasing temperature, and increased significantly at high moisture level (90% WHC)/suboxic conditions. Our findings reveal that the responses of microbial CUE and microbial biomass turnover to short-term temperature and moisture/O2 changes depended mainly on microbial growth responses and less on respiration responses to the environmental cues, which were consistent across soils differing in land use and geology.
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Affiliation(s)
- Qing Zheng
- Department of Microbiology and Ecosystem Science, Research Network “Chemistry Meets Microbiology”, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Yuntao Hu
- Department of Microbiology and Ecosystem Science, Research Network “Chemistry Meets Microbiology”, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Shasha Zhang
- Department of Microbiology and Ecosystem Science, Research Network “Chemistry Meets Microbiology”, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Lisa Noll
- Department of Microbiology and Ecosystem Science, Research Network “Chemistry Meets Microbiology”, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Theresa Böckle
- Department of Microbiology and Ecosystem Science, Research Network “Chemistry Meets Microbiology”, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Andreas Richter
- Department of Microbiology and Ecosystem Science, Research Network “Chemistry Meets Microbiology”, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Wolfgang Wanek
- Department of Microbiology and Ecosystem Science, Research Network “Chemistry Meets Microbiology”, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
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10
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Arreghini S, de Cabo L, Serafini RJM, Fabrizio de Iorio A. Shoot litter breakdown and zinc dynamics of an aquatic plant, Schoenoplectus californicus. INTERNATIONAL JOURNAL OF PHYTOREMEDIATION 2018; 20:780-788. [PMID: 29775103 DOI: 10.1080/15226514.2018.1425667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Decomposition of plant debris is an important process in determining the structure and function of aquatic ecosystems. The aims were to find a mathematic model fitting the decomposition process of Schoenoplectus californicus shoots containing different Zn concentrations; compare the decomposition rates; and assess metal accumulation/mobilization during decomposition. A litterbag technique was applied with shoots containing three levels of Zn: collected from an unpolluted river (RIV) and from experimental populations at low (LoZn) and high (HiZn) Zn supply. The double exponential model explained S. californicus shoot decomposition, at first, higher initial proportion of refractory fraction in RIV detritus determined a lower decay rate and until 68 days, RIV and LoZn detritus behaved like a source of metal, releasing soluble/weakly bound zinc into the water; after 68 days, they became like a sink. However, HiZn detritus showed rapid release into the water during the first 8 days, changing to the sink condition up to 68 days, and then returning to the source condition up to 369 days. The knowledge of the role of detritus (sink/source) will allow defining a correct management of the vegetation used for zinc removal and providing a valuable tool for environmental remediation and rehabilitation planning.
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Affiliation(s)
- Silvana Arreghini
- a Cátedra de Química Inorgánica y Analítica , Departamento de Recursos Naturales y Ambiente , Facultad de Agronomía, Universidad de Buenos Aires , Buenos Aires , Argentina
| | - Laura de Cabo
- b CONICET-Museo Argentino de Ciencias Naturales "Bernardino Rivadavia," Buenos Aires , Argentina
| | - Roberto José María Serafini
- a Cátedra de Química Inorgánica y Analítica , Departamento de Recursos Naturales y Ambiente , Facultad de Agronomía, Universidad de Buenos Aires , Buenos Aires , Argentina
| | - Alicia Fabrizio de Iorio
- a Cátedra de Química Inorgánica y Analítica , Departamento de Recursos Naturales y Ambiente , Facultad de Agronomía, Universidad de Buenos Aires , Buenos Aires , Argentina
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11
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Grasset C, Mendonça R, Villamor Saucedo G, Bastviken D, Roland F, Sobek S. Large but variable methane production in anoxic freshwater sediment upon addition of allochthonous and autochthonous organic matter. LIMNOLOGY AND OCEANOGRAPHY 2018; 63:1488-1501. [PMID: 30166689 PMCID: PMC6108407 DOI: 10.1002/lno.10786] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 11/24/2017] [Accepted: 01/02/2018] [Indexed: 05/04/2023]
Abstract
An important question in the context of climate change is to understand how CH4 production is regulated in anoxic sediments of lakes and reservoirs. The type of organic carbon (OC) present in lakes is a key factor controlling CH4 production at anoxic conditions, but the studies investigating the methanogenic potential of the main OC types are fragmented. We incubated different types of allochthonous OC (alloOC; terrestrial plant leaves) and autochthonous OC (autoOC; phytoplankton and two aquatic plants species) in an anoxic sediment during 130 d. We tested if (1) the supply of fresh alloOC and autoOC to an anoxic refractory sediment would fuel CH4 production and if (2) autoOC would decompose faster than alloOC. The addition of fresh OC greatly increased CH4 production and the δ13C-CH4 partitioning indicated that CH4 originated exclusively from the fresh OC. The large CH4 production in an anoxic sediment fueled by alloOC is a new finding which indicates that all systems with anoxic conditions and high sedimentation rates have the potential to be CH4 emitters. The autoOC decomposed faster than alloOC, but the total CH4 production was not higher for all autoOC types, one aquatic plant species having values as low as the terrestrial leaves, and the other one having values as high as phytoplankton. Our study is the first to report such variability, suggesting that the extent to which C fixed by aquatic plants is emitted as greenhouse gases or buried as OC in sediment could more generally differ between aquatic vegetation types.
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Affiliation(s)
- Charlotte Grasset
- Laboratory of Aquatic Ecology, Department of BiologyFederal University of Juiz de ForaJuiz de ForaBrazil
- Limnology, Department of Ecology and GeneticsUppsala UniversityUppsalaSweden
| | - Raquel Mendonça
- Laboratory of Aquatic Ecology, Department of BiologyFederal University of Juiz de ForaJuiz de ForaBrazil
- Limnology, Department of Ecology and GeneticsUppsala UniversityUppsalaSweden
| | - Gabriella Villamor Saucedo
- Laboratory of Aquatic Ecology, Department of BiologyFederal University of Juiz de ForaJuiz de ForaBrazil
- Limnology, Department of Ecology and GeneticsUppsala UniversityUppsalaSweden
| | - David Bastviken
- Department of Thematic Studies – Environmental ChangeLinköping UniversityLinköpingSweden
| | - Fabio Roland
- Laboratory of Aquatic Ecology, Department of BiologyFederal University of Juiz de ForaJuiz de ForaBrazil
| | - Sebastian Sobek
- Limnology, Department of Ecology and GeneticsUppsala UniversityUppsalaSweden
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12
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Andrei AŞ, Baricz A, Robeson MS, Păuşan MR, Tămaş T, Chiriac C, Szekeres E, Barbu-Tudoran L, Levei EA, Coman C, Podar M, Banciu HL. Hypersaline sapropels act as hotspots for microbial dark matter. Sci Rep 2017; 7:6150. [PMID: 28733590 PMCID: PMC5522462 DOI: 10.1038/s41598-017-06232-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 06/12/2017] [Indexed: 12/04/2022] Open
Abstract
Present-day terrestrial analogue sites are crucial ground truth proxies for studying life in geochemical conditions close to those assumed to be present on early Earth or inferred to exist on other celestial bodies (e.g. Mars, Europa). Although hypersaline sapropels are border-of-life habitats with moderate occurrence, their microbiological and physicochemical characterization lags behind. Here, we study the diversity of life under low water activity by describing the prokaryotic communities from two disparate hypersaline sapropels (Transylvanian Basin, Romania) in relation to geochemical milieu and pore water chemistry, while inferring their role in carbon cycling by matching taxa to known taxon-specific biogeochemical functions. The polyphasic approach combined deep coverage SSU rRNA gene amplicon sequencing and bioinformatics with RT-qPCR and physicochemical investigations. We found that sapropels developed an analogous elemental milieu and harbored prokaryotes affiliated with fifty-nine phyla, among which the most abundant were Proteobacteria, Bacteroidetes and Chloroflexi. Containing thirty-two candidate divisions and possibly undocumented prokaryotic lineages, the hypersaline sapropels were found to accommodate one of the most diverse and novel ecosystems reported to date and may contribute to completing the phylogenetic branching of the tree of life.
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Affiliation(s)
- Adrian-Ştefan Andrei
- Department of Molecular Biology and Biotechnology, Faculty of Biology and Geology, Babeş-Bolyai University, Cluj-Napoca, Romania. .,Institute of Hydrobiology, Department of Aquatic Microbial Ecology, Biology Center of the Academy of Sciences of the Czech Republic, České Budějovice, Czech Republic.
| | - Andreea Baricz
- National Institute of Research and Development for Biological Sciences (NIRDBS), Institute of Biological Research, Cluj-Napoca, Romania
| | - Michael Scott Robeson
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.,Interstitial Genomics, LLC, Longmont, 80501, Colorado, USA
| | | | - Tudor Tămaş
- Department of Geology, Faculty of Biology and Geology, Babeş-Bolyai University, Cluj-Napoca, Romania
| | - Cecilia Chiriac
- Department of Molecular Biology and Biotechnology, Faculty of Biology and Geology, Babeş-Bolyai University, Cluj-Napoca, Romania.,National Institute of Research and Development for Biological Sciences (NIRDBS), Institute of Biological Research, Cluj-Napoca, Romania
| | - Edina Szekeres
- Department of Molecular Biology and Biotechnology, Faculty of Biology and Geology, Babeş-Bolyai University, Cluj-Napoca, Romania.,National Institute of Research and Development for Biological Sciences (NIRDBS), Institute of Biological Research, Cluj-Napoca, Romania
| | - Lucian Barbu-Tudoran
- Department of Molecular Biology and Biotechnology, Faculty of Biology and Geology, Babeş-Bolyai University, Cluj-Napoca, Romania
| | - Erika Andrea Levei
- INCDO-INOE 2000, Research Institute for Analytical Instrumentation, Cluj-Napoca, Romania
| | - Cristian Coman
- National Institute of Research and Development for Biological Sciences (NIRDBS), Institute of Biological Research, Cluj-Napoca, Romania
| | - Mircea Podar
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Horia Leonard Banciu
- Department of Molecular Biology and Biotechnology, Faculty of Biology and Geology, Babeş-Bolyai University, Cluj-Napoca, Romania.
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13
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Zoppini A, Ademollo N, Amalfitano S, Casella P, Patrolecco L, Polesello S. Organic priority substances and microbial processes in river sediments subject to contrasting hydrological conditions. THE SCIENCE OF THE TOTAL ENVIRONMENT 2014; 484:74-83. [PMID: 24686147 DOI: 10.1016/j.scitotenv.2014.03.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 02/25/2014] [Accepted: 03/05/2014] [Indexed: 05/25/2023]
Abstract
Flood and drought events of higher intensity and frequency are expected to increase in arid and semi-arid regions, in which temporary rivers represent both a water resource and an aquatic ecosystem to be preserved. In this study, we explored the variation of two classes of hazardous substances (Polycyclic Aromatic Hydrocarbons and Nonylphenols) and the functioning of the microbial community in river sediments subject to hydrological fluctuations (Candelaro river basin, Italy). Overall, the concentration of pollutants (∑PAHs range 8-275ngg(-1); ∑NPs range 299-4858ngg(-1)) suggests a moderate degree of contamination. The conditions in which the sediments were tested, flow (high/low) and no flow (wet/dry/arid), were associated to significant differences in the chemical and microbial properties. The total organic carbon contribution decreased together with the stream flow reduction, while the contribution of C-PAHs and C-NPs tended to increase. NPs were relatively more concentrated in sediments under high flow, while the more hydrophobic PAHs accumulated under low and no flow conditions. Passing from high to no flow conditions, a gradual reduction of microbial processes was observed, to reach the lowest specific bacterial carbon production rates (0.06fmolCh(-1)cell(-1)), extracellular enzyme activities, and the highest doubling time (40h) in arid sediments. In conclusion, different scenarios for the mobilization of pollutants and microbial processes can be identified under contrasting hydrological conditions: (i) the mobilization of pollutants under high flow and a relatively higher probability for biodegradation; (ii) the accumulation of pollutants during low flow and lower probability for biodegradation; (iii) the drastic reduction of pollutant concentrations under dry and arid conditions, probably independently from the microbial activity (abiotic processes). Our findings let us infer that a multiple approach has to be considered for an appropriate water resource exploitation and a more realistic prevision of the impact of pollutants in temporary waters.
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Affiliation(s)
- Annamaria Zoppini
- Istituto di Ricerca Sulle Acque, Consiglio Nazionale delle Ricerche (IRSA-CNR), Via Salaria, Km 29.300, CP10, 00015 Monterotondo (Roma), Italy.
| | - Nicoletta Ademollo
- Istituto di Ricerca Sulle Acque, Consiglio Nazionale delle Ricerche (IRSA-CNR), Via Salaria, Km 29.300, CP10, 00015 Monterotondo (Roma), Italy
| | - Stefano Amalfitano
- Istituto di Ricerca Sulle Acque, Consiglio Nazionale delle Ricerche (IRSA-CNR), Via Salaria, Km 29.300, CP10, 00015 Monterotondo (Roma), Italy
| | - Patrizia Casella
- Istituto di Ricerca Sulle Acque, Consiglio Nazionale delle Ricerche (IRSA-CNR), Via Salaria, Km 29.300, CP10, 00015 Monterotondo (Roma), Italy
| | - Luisa Patrolecco
- Istituto di Ricerca Sulle Acque, Consiglio Nazionale delle Ricerche (IRSA-CNR), Via Salaria, Km 29.300, CP10, 00015 Monterotondo (Roma), Italy
| | - Stefano Polesello
- Istituto di Ricerca Sulle Acque, Consiglio Nazionale delle Ricerche, (IRSA-CNR), Via del Mulino 19, 20861 Brugherio (MB), Italy
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14
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Canterle EB, da Motta Marques D, Rodrigues LR. Development of temporary subtropical wetlands induces higher gas production. Front Microbiol 2013; 4:56. [PMID: 23508352 PMCID: PMC3597979 DOI: 10.3389/fmicb.2013.00056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 02/26/2013] [Indexed: 11/13/2022] Open
Abstract
Temporary wetlands are short-term alternative ecosystems formed by flooding for irrigation of areas used for rice farming. The goal of this study is to describe the development cycle of rice fields as temporary wetlands in southern Brazil, evaluating how this process affect the gas production (CH4 and CO2) in soil with difference % carbon and organic matter content. Two areas adjacent to Lake Mangueira in southern Brazil were used during a rice-farming cycle. One area had soil containing 1.1% carbon and 2.4% organic matter, and the second area had soil with 2.4% carbon and 4.4% organic matter. The mean rates of gas production were 0.04 ± 0.02 mg CH4 m−2 d−1 and 1.18 ± 0.30 mg CO2 m−2 d−1 in the soil area with the lower carbon content, and 0.02 ± 0.03 mg CH4 m−2 d−1 and 1.38 ± 0.41 mg CO2 m−2 d−1 in the soil area with higher carbon content. Our results showed that mean rates of CO2 production were higher than those of CH4 in both areas. No statistically significant difference was observed for production of CH4 considering different periods and sites. For carbon dioxide (CO2), however, a Two-Way ANOVA showed statistically significant difference (p = 0.05) considering sampling time, but no difference between areas. The results obtained suggest that the carbon and organic matter contents in the soil of irrigated rice cultivation areas may have been used in different ways by soil microorganisms, leading to variations in CH4 and CO2 production.
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Affiliation(s)
- Eliete B Canterle
- Laboratório de Ecotecnologia e Limnologia, Instituto de Pesquisas Hidráulicas, Universidade Federal do Rio Grande do Sul Porto Alegre, Brazil
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15
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Harrison MD, Groffman PM, Mayer PM, Kaushal SS, Newcomer TA. Denitrification in alluvial wetlands in an urban landscape. JOURNAL OF ENVIRONMENTAL QUALITY 2011; 40:634-646. [PMID: 21520770 DOI: 10.2134/jeq2010.0335] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Riparian wetlands have been shown to be effective "sinks" for nitrate N (NO3-), minimizing the downstream export of N to streams and coastal water bodies. However, the vast majority of riparian denitrification research has been in agricultural and forested watersheds, with relatively little work on riparian wetland function in urban watersheds. We investigated the variation and magnitude of denitrification in three constructed and two relict oxbow urban wetlands, and in two forested reference wetlands in the Baltimore metropolitan area. Denitrification rates in wetland sediments were measured with a 15N-enriched NO3- "push-pull" groundwater tracer method during the summer and winter of 2008. Mean denitrification rates did not differ among the wetland types and ranged from 147 +/- 29 microg N kg soil(-1) d(-1) in constructed stormwater wetlands to 100 +/- 11 microg N kg soil(-1) d(-1) in relict oxbows to 106 +/- 32 microg N kg soil(-1) d(-1) in forested reference wetlands. High denitrification rates were observed in both summer and winter, suggesting that these wetlands are sinks for NO3- year round. Comparison of denitrification rates with NO3- standing stocks in the wetland water column and stream NO3- loads indicated that mass removal of NO3- in urban wetland sediments by denitrification could be substantial. Our results suggest that urban wetlands have the potential to reduce NO3- in urban landscapes and should be considered as a means to manage N in urban watersheds.
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Affiliation(s)
- Melanie D Harrison
- Marine Estuarine and Environmental Science Program, Univ. of Maryland Baltimore County, 1000 Hilltop Cir., Baltimore, MD 21250, USA.
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16
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Premke K, Karlsson J, Steger K, Gudasz C, von Wachenfeldt E, Tranvik LJ. Stable isotope analysis of benthic fauna and their food sources in boreal lakes. ACTA ACUST UNITED AC 2010. [DOI: 10.1899/10-002.1] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Katrin Premke
- Limnology, Department of Ecology and Evolution, EBC, Uppsala University, Norbyvägen 18 D, 75 236 Uppsala, Sweden
| | - Jan Karlsson
- Climate Impacts Research Centre (CIRC), Department of Ecology and Environmental Science, Umeå University, Sweden
| | - Kristin Steger
- Limnology, Department of Ecology and Evolution, EBC, Uppsala University, Norbyvägen 18 D, 75 236 Uppsala, Sweden
| | - Cristian Gudasz
- Limnology, Department of Ecology and Evolution, EBC, Uppsala University, Norbyvägen 18 D, 75 236 Uppsala, Sweden
| | - Eddie von Wachenfeldt
- Limnology, Department of Ecology and Evolution, EBC, Uppsala University, Norbyvägen 18 D, 75 236 Uppsala, Sweden
| | - Lars J. Tranvik
- Limnology, Department of Ecology and Evolution, EBC, Uppsala University, Norbyvägen 18 D, 75 236 Uppsala, Sweden
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17
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Carbon cycling in the Mesopelagic Zone of the central Arabian Sea: Results from a simple model. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2007gm000686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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18
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Effects of bacterial dynamics on organic matter decomposition and nutrient release from sediments: A modeling study. Ecol Modell 2008. [DOI: 10.1016/j.ecolmodel.2007.06.026] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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19
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Buesing N, Gessner MO. Benthic bacterial and fungal productivity and carbon turnover in a freshwater marsh. Appl Environ Microbiol 2006; 72:596-605. [PMID: 16391096 PMCID: PMC1352256 DOI: 10.1128/aem.72.1.596-605.2006] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Heterotrophic bacteria and fungi are widely recognized as crucial mediators of carbon, nutrient, and energy flow in ecosystems, yet information on their total annual production in benthic habitats is lacking. To assess the significance of annual microbial production in a structurally complex system, we measured production rates of bacteria and fungi over an annual cycle in four aerobic habitats of a littoral freshwater marsh. Production rates of fungi in plant litter were substantial (0.2 to 2.4 mg C g(-1) C) but were clearly outweighed by those of bacteria (2.6 to 18.8 mg C g(-1) C) throughout the year. This indicates that bacteria represent the most actively growing microorganisms on marsh plant litter in submerged conditions, a finding that contrasts strikingly with results from both standing dead shoots of marsh plants and submerged plant litter decaying in streams. Concomitant measurements of microbial respiration (1.5 to 15.3 mg C-CO2 g(-1) of plant litter C day(-1)) point to high microbial growth efficiencies on the plant litter, averaging 45.5%. The submerged plant litter layer together with the thin aerobic sediment layer underneath (average depth of 5 mm) contributed the bulk of microbial production per square meter of marsh surface (99%), whereas bacterial production in the marsh water column and epiphytic biofilms was negligible. The magnitude of the combined production in these compartments (approximately 1,490 g C m(-2) year(-1)) highlights the importance of carbon flows through microbial biomass, to the extent that even massive primary productivity of the marsh plants (603 g C m(-2) year(-1)) and subsidiary carbon sources (approximately 330 g C m(-2) year(-1)) were insufficient to meet the microbial carbon demand. These findings suggest that littoral freshwater marshes are genuine hot spots of aerobic microbial carbon transformations, which may act as net organic carbon importers from adjacent systems and, in turn, emit large amounts of CO2 (here, approximately 870 g C m(-2) year(-1)) into the atmosphere.
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Affiliation(s)
- Nanna Buesing
- Department of Limnology, Swiss Federal Institute of Aquatic Science and Technology (Eawag/ETH), 6047 Kastanienbaum, Switzerland.
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