Organic carbon turnover time in deep-sea benthos

1990 ◽  
Vol 24 (1-4) ◽  
pp. 141-160 ◽  
Author(s):  
Gilbert T Rowe ◽  
Myriam Sibuet ◽  
Jody Deming ◽  
John Tietjen ◽  
Alexis Khripounoff
Keyword(s):  
Organic Carbon ◽  
Deep Sea ◽  
Turnover Time ◽  
Carbon Turnover

scholarly journals Short organic carbon turnover time and narrow 14 C age spectra in early Holocene wetland paleosols

2017 ◽  
Vol 18 (1) ◽  
pp. 142-155 ◽  
Author(s):  
Lael Vetter ◽  
Brad E. Rosenheim ◽  
Alvaro Fernandez ◽  
Torbjörn E. Törnqvist
Keyword(s):  
Organic Carbon ◽  
Turnover Time ◽  
Early Holocene ◽  
Carbon Turnover

scholarly journals Fire-derived organic carbon turnover in soils on a centennial scale

2011 ◽  
Vol 8 (6) ◽  
pp. 12179-12195
Author(s):  
N. Singh ◽  
S. Abiven ◽  
M. S. Torn ◽  
M. W. I. Schmidt
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
Pyrolysis Temperature ◽  
Plant Biomass ◽  
Meta Analysis ◽  
Turnover Time ◽  
Carbon Turnover ◽  
Biomass Pyrolysis ◽  
Pyrogenic Carbon

Abstract. Pyrogenic Carbon (PyC), the residue of an incomplete combustion of plant biomass, is considered as a carbon (C) sink due to its assumed stability in soil. Our meta-analysis of studies on PyC degradation challenges the assumption that PyC persist in soil for several thousand years. The turnover time for PyC estimated here ranges from decadal to centennial time scales, and is not slower than decomposition of bulk Soil Organic Matter (SOM) and differs with initial biomass, pyrolysis temperature and climate. Thus, using PyC as a strategy for offsetting carbon emissions requires caution and further research.

Plant carbon inputs through shoot, root, and mycorrhizal pathways affect soil organic carbon turnover differently

2021 ◽  
pp. 108322
Author(s):  
Junsheng Huang ◽  
Weixing Liu ◽  
Sen Yang ◽  
Lu Yang ◽  
Ziyang Peng ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Carbon Turnover

Subsoil organic carbon turnover is dominantly controlled by soil properties in grasslands across China

2021 ◽  
Author(s):  
Yuehong Shi ◽  
Xiaolu Tang ◽  
Peng Yu ◽  
Li Xu ◽  
Guo Chen ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Soil Properties ◽  
Soil Carbon ◽  
Carbon Turnover ◽  
Area Index ◽  
Important Indicator ◽  
Environmental Controls ◽  
Biogeochemical Models ◽  
Soc Stock

<p>Soil carbon turnover time (τ, year) is an important indicator of soil carbon stability, and a major factor in determining soil carbon sequestration capacity. Many studies investigated τ in the topsoil or the first meter underground, however, little is known about subsoil τ (0.2 – 1.0 m) and its environmental drivers, while world subsoils below 0.2 m accounts for the majority of total soil organic carbon (SOC) stock and may be as sensitive as that of the topsoil to climate change. We used the observations from the published literatures to estimate subsoil τ (the ratio of SOC stock to net primary productivity) in grasslands across China and employed regression analysis to detect the environmental controls on subsoil τ. Finally, structural equation modelling (SEM) was applied to identify the dominant environmental driver (including climate, vegetation and soil). Results showed that subsoil τ varied greatly from 5.52 to 702.17 years, and the mean (± standard deviation) subsoil τ was 118.5 ± 97.8 years. Subsoil τ varied significantly among different grassland types that it was 164.0 ± 112.0 years for alpine meadow, 107.0 ± 47.9 years for alpine steppe, 177.0 ± 143.0 years for temperate desert steppe, 96.6 ± 88.7 years for temperate meadow steppe, 101.0 ± 75.9 years for temperate typical steppe. Subsoil τ significantly and negatively correlated (p < 0.05) with vegetation index, leaf area index and gross primary production, highlighting the importance of vegetation on τ. Mean annual temperature (MAT) and precipitation (MAP) had a negative impact on subsoil τ, indicating a faster turnover of soil carbon with the increasing of MAT or MAP under ongoing climate change. SEM showed that soil properties, such as soil bulk density, cation exchange capacity and soil silt, were the most important variables driving subsoil τ, challenging our current understanding of climatic drivers (MAT and MAP) controlling on topsoil τ, further providing new evidence that different mechanisms control topsoil and subsoil τ. These conclusions demonstrated that different environmental controls should be considered for reliable prediction of soil carbon dynamics in the top and subsoils in biogeochemical models or earth system models at regional or global scales.</p>

scholarly journals Reviews and syntheses: Hidden forests, the role of vegetated coastal habitats in the ocean carbon budget

2017 ◽  
Vol 14 (2) ◽  
pp. 301-310 ◽  
Author(s):  
Carlos M. Duarte
Keyword(s):  
Carbon Sequestration ◽  
Organic Carbon ◽  
Primary Production ◽  
Deep Sea ◽  
Carbon Budget ◽  
Net Primary Production ◽  
Global Ocean ◽  
Coastal Habitats ◽  
Global Carbon Budget ◽  
Global Carbon

Abstract. Vegetated coastal habitats, including seagrass and macroalgal beds, mangrove forests and salt marshes, form highly productive ecosystems, but their contribution to the global carbon budget remains overlooked, and these forests remain hidden in representations of the global carbon budget. Despite being confined to a narrow belt around the shoreline of the world's oceans, where they cover less than 7 million km2, vegetated coastal habitats support about 1 to 10 % of the global marine net primary production and generate a large organic carbon surplus of about 40 % of their net primary production (NPP), which is either buried in sediments within these habitats or exported away. Large, 10-fold uncertainties in the area covered by vegetated coastal habitats, along with variability about carbon flux estimates, result in a 10-fold bracket around the estimates of their contribution to organic carbon sequestration in sediments and the deep sea from 73 to 866 Tg C yr−1, representing between 3 % and 1∕3 of oceanic CO2 uptake. Up to 1∕2 of this carbon sequestration occurs in sink reservoirs (sediments or the deep sea) beyond these habitats. The organic carbon exported that does not reach depositional sites subsidizes the metabolism of heterotrophic organisms. In addition to a significant contribution to organic carbon production and sequestration, vegetated coastal habitats contribute as much to carbonate accumulation as coral reefs do. While globally relevant, the magnitude of global carbon fluxes supported by salt-marsh, mangrove, seagrass and macroalgal habitats is declining due to rapid habitat loss, contributing to loss of CO2 sequestration, storage capacity and carbon subsidies. Incorporating the carbon fluxes' vegetated coastal habitats' support into depictions of the carbon budget of the global ocean and its perturbations will improve current representations of the carbon budget of the global ocean.

Substantial accumulation of mercury in the deepest parts of the ocean and implications for the environmental mercury cycle

2021 ◽  
Vol 118 (51) ◽  
pp. e2102629118
Author(s):  
Maodian Liu ◽  
Wenjie Xiao ◽  
Qianru Zhang ◽  
Shengliu Yuan ◽  
Peter A. Raymond ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Food Webs ◽  
Deep Sea ◽  
Anthropogenic Activities ◽  
Sediment Cores ◽  
Anthropogenic Sources ◽  
Biogeochemical Cycle ◽  
Vertical Profiles ◽  
Surface Ocean ◽  
Increasing Trends

Anthropogenic activities have led to widespread contamination with mercury (Hg), a potent neurotoxin that bioaccumulates through food webs. Recent models estimated that, presently, 200 to 600 t of Hg is sequestered annually in deep-sea sediments, approximately doubling since industrialization. However, most studies did not extend to the hadal zone (6,000- to 11,000-m depth), the deepest ocean realm. Here, we report on measurements of Hg and related parameters in sediment cores from four trench regions (1,560 to 10,840 m), showing that the world’s deepest ocean realm is accumulating Hg at remarkably high rates (depth-integrated minimum–maximum: 24 to 220 μg ⋅ m−2 ⋅ y−1) greater than the global deep-sea average by a factor of up to 400, with most Hg in these trenches being derived from the surface ocean. Furthermore, vertical profiles of Hg concentrations in trench cores show notable increasing trends from pre-1900 [average 51 ± 14 (1σ) ng ⋅ g−1] to post-1950 (81 ± 32 ng ⋅ g−1). This increase cannot be explained by changes in the delivery rate of organic carbon alone but also need increasing Hg delivery from anthropogenic sources. This evidence, along with recent findings on the high abundance of methylmercury in hadal biota [R. Sun et al., Nat. Commun. 11, 3389 (2020); J. D. Blum et al., Proc. Natl. Acad. Sci. U. S. A. 117, 29292–29298 (2020)], leads us to propose that hadal trenches are a large marine sink for Hg and may play an important role in the regulation of the global biogeochemical cycle of Hg.

scholarly journals Large deep-sea zooplankton biomass mirrors primary production in the global ocean

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Hernández-León ◽  
R. Koppelmann ◽  
E. Fraile-Nuez ◽  
A. Bode ◽  
C. Mompeán ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Deep Sea ◽  
Large Scale ◽  
Net Primary Production ◽  
Deep Ocean ◽  
Zooplankton Biomass ◽  
Global Ocean ◽  
Global Coupling ◽  
Do So

AbstractThe biological pump transports organic carbon produced by photosynthesis to the meso- and bathypelagic zones, the latter removing carbon from exchanging with the atmosphere over centennial time scales. Organisms living in both zones are supported by a passive flux of particles, and carbon transported to the deep-sea through vertical zooplankton migrations. Here we report globally-coherent positive relationships between zooplankton biomass in the epi-, meso-, and bathypelagic layers and average net primary production (NPP). We do so based on a global assessment of available deep-sea zooplankton biomass data and large-scale estimates of average NPP. The relationships obtained imply that increased NPP leads to enhanced transference of organic carbon to the deep ocean. Estimated remineralization from respiration rates by deep-sea zooplankton requires a minimum supply of 0.44 Pg C y−1 transported into the bathypelagic ocean, comparable to the passive carbon sequestration. We suggest that the global coupling between NPP and bathypelagic zooplankton biomass must be also supported by an active transport mechanism associated to vertical zooplankton migration.

scholarly journals Lessons learned from the monitoring of turbidity currents and guidance for future platform designs

2020 ◽  
Vol 500 (1) ◽  
pp. 605-634 ◽  
Author(s):  
Michael Clare ◽  
D. Gwyn Lintern ◽  
Kurt Rosenberger ◽  
John E. Hughes Clarke ◽  
Charles Paull ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Engineering Design ◽  
Surface Area ◽  
Deep Sea ◽  
Critical Infrastructure ◽  
Lessons Learned ◽  
Turbidity Currents ◽  
Improve Design ◽  
Current Behaviour ◽  
Water Depths

AbstractTurbidity currents transport globally significant volumes of sediment and organic carbon into the deep-sea and pose a hazard to critical infrastructure. Despite advances in technology, their powerful nature often damages expensive instruments placed in their path. These challenges mean that turbidity currents have only been measured in a few locations worldwide, in relatively shallow water depths (<<2 km). Here, we share lessons from recent field deployments about how to design the platforms on which instruments are deployed. First, we show how monitoring platforms have been affected by turbidity currents including instability, displacement, tumbling and damage. Second, we relate these issues to specifics of the platform design, such as exposure of large surface area instruments within a flow and inadequate anchoring or seafloor support. Third, we provide recommended modifications to improve design by simplifying mooring configurations, minimizing surface area and enhancing seafloor stability. Finally, we highlight novel multi-point moorings that avoid interaction between the instruments and the flow, and flow-resilient seafloor platforms with innovative engineering design features, such as feet and ballast that can be ejected. Our experience will provide guidance for future deployments, so that more detailed insights can be provided into turbidity current behaviour, in a wider range of settings.

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