1
|
Wei Z, Du Z, Wang L, Zhong W, Lin J, Xu Q, Xiao C. Sedimentary organic carbon storage of thermokarst lakes and ponds across Tibetan permafrost region. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 831:154761. [PMID: 35339557 DOI: 10.1016/j.scitotenv.2022.154761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Revised: 03/15/2022] [Accepted: 03/18/2022] [Indexed: 06/14/2023]
Abstract
Sedimentary soil organic carbon (SOC) stored in thermokarst lakes and ponds (hereafter referred to as thaw lakes) across high-latitude/altitude permafrost areas is of global significance due to increasing thaw lake numbers and their high C vulnerability under climate warming. However, to date, little is known about the SOC storage in these lakes, which limits our better understanding of the fate of these active carbon in a warming future. Here, by combining large-scale field observation data and published deep (e.g., 0-300 cm) permafrost SOC data with a random forest (RF) machine learning technique, we provided the first comprehensive estimation of thaw lake SOC stocks to 3 m depth on the Tibetan Plateau. This study demonstrated that combining multiple environmental factors with the RF model could effectively predict the spatial distributions of the thaw lake SOC density values (SOCDs). The model results revealed that the soil respiration, normalized difference vegetation index (NDVI), and mean annual precipitation (MAP) were the most influential factors for predicting thaw lake SOCDs. In total, the sedimentary SOC stocks in the thaw lakes were approximately 52.62 Tg in the top 3 m, with 53% of the SOC stored in the upper layers (0-100 cm). The SOCDs generally exhibited high values in eastern Tibetan Plateau, and low values in mid- and western Tibetan Plateau, which were similar to the patterns of the land cover types that affected the SOCDs. We further found that the SOCDs of thaw lakes were generally higher than those of their surrounding permafrost soils at different layer depths, which could be ascribed to the erosion of soil particles or leaching solution from the thawing permafrost soils to lakes and/or enhanced vegetation growth at the lake bottom. This research highlights the necessity of explicitly considering the thaw lake SOC stocks in Earth system models for more comprehensive future projections of the carbon dynamics on the plateau.
Collapse
Affiliation(s)
- Zhiqiang Wei
- Zhuhai Branch of State Key Laboratory of Earth Surface Process and Resource Ecology, Beijing Normal University, Zhuhai 519087, China
| | - Zhiheng Du
- State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Lei Wang
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China
| | - Wei Zhong
- School of Geography Sciences, South China Normal University, Guangzhou 510631, China
| | - Jiahui Lin
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China
| | - Qian Xu
- State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Cunde Xiao
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China.
| |
Collapse
|
2
|
von Jackowski A, Grosse J, Nöthig EM, Engel A. Dynamics of organic matter and bacterial activity in the Fram Strait during summer and autumn. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20190366. [PMID: 32862814 PMCID: PMC7481659 DOI: 10.1098/rsta.2019.0366] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/13/2020] [Indexed: 05/12/2023]
Abstract
The Arctic Ocean is considerably affected by the consequences of global warming, including more extreme seasonal fluctuations in the physical environment. So far, little is known about seasonality in Arctic marine ecosystems in particular microbial dynamics and cycling of organic matter. The limited characterization can be partially attributed to logistic difficulties of sampling in the Arctic Ocean beyond the summer season. Here, we investigated the distribution and composition of dissolved organic matter (DOM), gel particles and heterotrophic bacterial activity in the Fram Strait during summer and autumn. Our results revealed that phytoplankton biomass influenced the concentration and composition of semi-labile dissolved organic carbon (DOC), which strongly decreased from summer to autumn. The seasonal decrease in bioavailability of DOM appeared to be the dominant control on bacterial abundance and activity, while no temperature effect was determined. Additionally, there were clear differences in transparent exopolymer particles (TEP) and Coomassie Blue stainable particles (CSP) dynamics. The amount of TEP and CSP decreased from summer to autumn, but CSP was relatively enriched in both seasons. Our study therewith indicates clear seasonal differences in the microbial cycling of organic matter in the Fram Strait. Our data may help to establish baseline knowledge about seasonal changes in microbial ecosystem dynamics to better assess the impact of environmental change in the warming Arctic Ocean. This article is part of the theme issue 'The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'.
Collapse
Affiliation(s)
| | - Julia Grosse
- GEOMAR Helmholz Centre for Ocean Research Kiel, Kiel, Germany
| | - Eva-Maria Nöthig
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Anja Engel
- GEOMAR Helmholz Centre for Ocean Research Kiel, Kiel, Germany
| |
Collapse
|
3
|
Fouilland E, Floc’h EL, Brennan D, Bell EM, Lordsmith SL, McNeill S, Mitchell E, Brand TD, García-Martín EE, Leakey RJG. Assessment of bacterial dependence on marine primary production along a northern latitudinal gradient. FEMS Microbiol Ecol 2018; 94:5067298. [DOI: 10.1093/femsec/fiy150] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 08/03/2018] [Indexed: 11/14/2022] Open
Affiliation(s)
- Eric Fouilland
- MARBEC Univ Montpellier, CNRS, IFREMER, IRD, av. Jean Monnet, 34200 Sète, France
| | - Emilie Le Floc’h
- MARBEC Univ Montpellier, CNRS, IFREMER, IRD, av. Jean Monnet, 34200 Sète, France
| | - Debra Brennan
- Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA, UK
| | - Elanor M Bell
- Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA, UK
- Australian Antarctic Division, 203 Channel Highway, Tasmania 7050, Australia
| | - Sian L Lordsmith
- Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA, UK
- Cardiff University, School of Earth and Ocean Sciences, 1.74B/3.01, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Sharon McNeill
- Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA, UK
| | - Elaine Mitchell
- Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA, UK
| | - Tim D Brand
- Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA, UK
| | - E Elena García-Martín
- Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Raymond JG Leakey
- Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA, UK
| |
Collapse
|
4
|
Monier A, Findlay HS, Charvet S, Lovejoy C. Late winter under ice pelagic microbial communities in the high Arctic Ocean and the impact of short-term exposure to elevated CO2 levels. Front Microbiol 2014; 5:490. [PMID: 25324832 PMCID: PMC4179612 DOI: 10.3389/fmicb.2014.00490] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 09/01/2014] [Indexed: 11/13/2022] Open
Abstract
Polar Oceans are natural CO2 sinks because of the enhanced solubility of CO2 in cold water. The Arctic Ocean is at additional risk of accelerated ocean acidification (OA) because of freshwater inputs from sea ice and rivers, which influence the carbonate system. Winter conditions in the Arctic are of interest because of both cold temperatures and limited CO2 venting to the atmosphere when sea ice is present. Earlier OA experiments on Arctic microbial communities conducted in the absence of ice cover, hinted at shifts in taxa dominance and diversity under lowered pH. The Catlin Arctic Survey provided an opportunity to conduct in situ, under-ice, OA experiments during late Arctic winter. Seawater was collected from under the sea ice off Ellef Ringnes Island, and communities were exposed to three CO2 levels for 6 days. Phylogenetic diversity was greater in the attached fraction compared to the free-living fraction in situ, in the controls and in the treatments. The dominant taxa in all cases were Gammaproteobacteria but acidification had little effect compared to the effects of containment. Phylogenetic net relatedness indices suggested that acidification may have decreased the diversity within some bacterial orders, but overall there was no clear trend. Within the experimental communities, alkalinity best explained the variance among samples and replicates, suggesting subtle changes in the carbonate system need to be considered in such experiments. We conclude that under ice communities have the capacity to respond either by selection or phenotypic plasticity to heightened CO2 levels over the short term.
Collapse
Affiliation(s)
- Adam Monier
- Département de Biologie, Québec Océan and Institut de Biologie Intégrative et des Systèmes, Université Laval Québec, QC, Canada ; Takuvik Joint International Laboratory (CNRS UMI-3376), Université Laval Québec, QC, Canada
| | | | - Sophie Charvet
- Département de Biologie, Québec Océan and Institut de Biologie Intégrative et des Systèmes, Université Laval Québec, QC, Canada
| | - Connie Lovejoy
- Département de Biologie, Québec Océan and Institut de Biologie Intégrative et des Systèmes, Université Laval Québec, QC, Canada ; Takuvik Joint International Laboratory (CNRS UMI-3376), Université Laval Québec, QC, Canada
| |
Collapse
|
5
|
A new highly sensitive method to assess respiration rates and kinetics of natural planktonic communities by use of the switchable trace oxygen sensor and reduced oxygen concentrations. PLoS One 2014; 9:e105399. [PMID: 25127458 PMCID: PMC4134296 DOI: 10.1371/journal.pone.0105399] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 07/22/2014] [Indexed: 11/19/2022] Open
Abstract
Oxygen respiration rates in pelagic environments are often difficult to quantify as the resolutions of our methods for O2 concentration determination are marginal for observing significant decreases during bottle incubations of less than 24 hours. Here we present the assessment of a new highly sensitive method, that combine Switchable Trace Oxygen (STOX) sensors and all-glass bottle incubations, where the O2 concentration was artificially lowered. The detection limit of respiration rate by this method is inversely proportional to the O2 concentration, down to <2 nmol L(-1) h(-1) for water with an initial O2 concentration of 500 nmol L(-1). The method was tested in Danish coastal waters and in oceanic hypoxic waters. It proved to give precise measurements also with low oxygen consumption rates (∼7 nmol L(-1) h(-1)), and to significantly decrease the time required for incubations (≤14 hours) compared to traditional methods. This method provides continuous real time measurements, allowing for a number of diverse possibilities, such as modeling the rate of oxygen decrease to obtain kinetic parameters. Our data revealed apparent half-saturation concentrations (Km values) one order of magnitude lower than previously reported for marine bacteria, varying between 66 and 234 nmol L(-1) O2. Km values vary between different microbial planktonic communities, but our data show that it is possible to measure reliable respiration rates at concentrations ∼0.5-1 µmol L(-1) O2 that are comparable to the ones measured at full air saturation.
Collapse
|
6
|
Urea uptake and carbon fixation by marine pelagic bacteria and archaea during the Arctic summer and winter seasons. Appl Environ Microbiol 2014; 80:6013-22. [PMID: 25063662 DOI: 10.1128/aem.01431-14] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
How Arctic climate change might translate into alterations of biogeochemical cycles of carbon (C) and nitrogen (N) with respect to inorganic and organic N utilization is not well understood. This study combined 15N uptake rate measurements for ammonium, nitrate, and urea with 15N- and 13C-based DNA stable-isotope probing (SIP). The objective was to identify active bacterial and archeal plankton and their role in N and C uptake during the Arctic summer and winter seasons. We hypothesized that bacteria and archaea would successfully compete for nitrate and urea during the Arctic winter but not during the summer, when phytoplankton dominate the uptake of these nitrogen sources. Samples were collected at a coastal station near Barrow, AK, during August and January. During both seasons, ammonium uptake rates were greater than those for nitrate or urea, and nitrate uptake rates remained lower than those for ammonium or urea. SIP experiments indicated a strong seasonal shift of bacterial and archaeal N utilization from ammonium during the summer to urea during the winter but did not support a similar seasonal pattern of nitrate utilization. Analysis of 16S rRNA gene sequences obtained from each SIP fraction implicated marine group I Crenarchaeota (MGIC) as well as Betaproteobacteria, Firmicutes, SAR11, and SAR324 in N uptake from urea during the winter. Similarly, 13C SIP data suggested dark carbon fixation for MGIC, as well as for several proteobacterial lineages and the Firmicutes. These data are consistent with urea-fueled nitrification by polar archaea and bacteria, which may be advantageous under dark conditions.
Collapse
|
7
|
Robbins LL, Wynn JG, Lisle JT, Yates KK, Knorr PO, Byrne RH, Liu X, Patsavas MC, Azetsu-Scott K, Takahashi T. Baseline monitoring of the western Arctic Ocean estimates 20% of Canadian basin surface waters are undersaturated with respect to aragonite. PLoS One 2013; 8:e73796. [PMID: 24040074 PMCID: PMC3770696 DOI: 10.1371/journal.pone.0073796] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 07/25/2013] [Indexed: 11/18/2022] Open
Abstract
Marine surface waters are being acidified due to uptake of anthropogenic carbon dioxide, resulting in surface ocean areas of undersaturation with respect to carbonate minerals, including aragonite. In the Arctic Ocean, acidification is expected to occur at an accelerated rate with respect to the global oceans, but a paucity of baseline data has limited our understanding of the extent of Arctic undersaturation and of regional variations in rates and causes. The lack of data has also hindered refinement of models aimed at projecting future trends of ocean acidification. Here, based on more than 34,000 data records collected in 2010 and 2011, we establish a baseline of inorganic carbon data (pH, total alkalinity, dissolved inorganic carbon, partial pressure of carbon dioxide, and aragonite saturation index) for the western Arctic Ocean. This data set documents aragonite undersaturation in ∼20% of the surface waters of the combined Canada and Makarov basins, an area characterized by recent acceleration of sea ice loss. Conservative tracer studies using stable oxygen isotopic data from 307 sites show that while the entire surface of this area receives abundant freshwater from meteoric sources, freshwater from sea ice melt is most closely linked to the areas of carbonate mineral undersaturation. These data link the Arctic Ocean’s largest area of aragonite undersaturation to sea ice melt and atmospheric CO2 absorption in areas of low buffering capacity. Some relatively supersaturated areas can be linked to localized biological activity. Collectively, these observations can be used to project trends of ocean acidification in higher latitude marine surface waters where inorganic carbon chemistry is largely influenced by sea ice meltwater.
Collapse
Affiliation(s)
- Lisa L. Robbins
- St. Petersburg Coastal and Marine Science Center, United States Geological Survey, St. Petersburg, Florida, United States of America
- * E-mail:
| | - Jonathan G. Wynn
- Department of Geology, University of South Florida, Tampa, Florida, United States of America
| | - John T. Lisle
- St. Petersburg Coastal and Marine Science Center, United States Geological Survey, St. Petersburg, Florida, United States of America
| | - Kimberly K. Yates
- St. Petersburg Coastal and Marine Science Center, United States Geological Survey, St. Petersburg, Florida, United States of America
| | - Paul O. Knorr
- St. Petersburg Coastal and Marine Science Center, United States Geological Survey, St. Petersburg, Florida, United States of America
| | - Robert H. Byrne
- College of Marine Science, University of South Florida, St. Petersburg, Florida, United States of America
| | - Xuewu Liu
- College of Marine Science, University of South Florida, St. Petersburg, Florida, United States of America
| | - Mark C. Patsavas
- College of Marine Science, University of South Florida, St. Petersburg, Florida, United States of America
| | - Kumiko Azetsu-Scott
- Ocean Sciences Division, Department of Fisheries and Oceans, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada
| | - Taro Takahashi
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, United States of America
| |
Collapse
|