scholarly journals Sedimentation Rate Estimation and Tracing Organic Carbon and Nutrients Sources in Sediment of Ha Long Bay (Vietnam)

2021 ◽  
Vol 7 (2) ◽  
Author(s):  
Thuan Dao Dinh ◽  
Long Nguyen Quang ◽  
Thang Duong Van ◽  
Nhan Dang Duc ◽  
Anh Ha Lan ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Sedimentation Rate ◽  
Rate Estimation ◽  
Long Bay

Total organic carbon and the preservation of organic-walled microfossils in Precambrian shale

Geology ◽  
2020 ◽  
Author(s):  
C.R. Woltz ◽  
S.M. Porter ◽  
H. Agić ◽  
C.M. Dehler ◽  
C.K. Junium ◽  
...  
Keyword(s):  
Species Richness ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Microbial Degradation ◽  
Sedimentation Rate ◽  
Surface Pattern ◽  
Causal Factors ◽  
Eukaryotic Diversity ◽  
High Concentrations ◽  
Fossil Preservation

Much of our understanding of early eukaryote diversity and paleoecology comes from the record of organic-walled microfossils in shale, yet the conditions controlling their preservation are not well understood. It has been suggested that high concentrations of total organic carbon (TOC) inhibit the preservation of organic fossils in shale, and although this idea is supported anecdotally, it has never been tested. Here we compared the presence, preservational quality, and assemblage diversity of organic-walled microfossils to TOC concentrations of 346 shale samples that span the late Paleoproterozoic to middle Neoproterozoic in age. We found that fossil-bearing samples have significantly lower median TOC values (0.32 wt%, n = 189) than those containing no fossils (0.72 wt%, n = 157). Preservational quality, measured by the loss of surface pattern, density of pitting, and deterioration of wall margin, decreases as TOC increases. Species richness negatively correlates with TOC within the ca. 750 Ma Chuar Group (Arizona, USA), but no relationship is observed in other units. These results support the hypothesis that high TOC content either decreases the preservational quality or inhibits the preservation of organic-walled microfossils altogether. However, it is also possible that other causal factors, including sedimentation rate and microbial degradation, account for the correlation between fossil preservation and TOC. We expect that as TOC varies in space and time, so too does the probability of finding well-preserved fossils. A compilation of 13,940 TOC values spanning Earth history suggests significantly higher median TOC levels in Mesoproterozoic versus Neoproterozoic shale, potentially biasing the interpreted pattern of increased eukaryotic diversity in the Tonian.

scholarly journals Coastal urbanization alters carbon cycling in Tokyo Bay

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Atsushi Kubo ◽  
Jota Kanda
Keyword(s):  
Organic Carbon ◽  
Sedimentation Rate ◽  
Dissolved Inorganic Carbon ◽  
Sewage Treatment ◽  
Tokyo Bay ◽  
Net Community Production ◽  
Labile Organic Carbon ◽  
Treatment Facilities ◽  
Coastal Urbanization ◽  
Freshwater Inputs

AbstractThe carbon budget of Tokyo Bay, a highly urbanized coastal basin, was estimated using a box model that incorporated inorganic and organic carbon data over an annual cycle (2011–2012). The surface water represented net autotrophic system in which the annual net community production (NCP) was 19 × 1010 gC year−1. The annual loading of dissolved inorganic carbon and total organic carbon (TOC) from freshwater inputs was 11.2 × 1010 and 4.9 × 1010 gC year−1, respectively. The annual TOC sedimentation rate was 3.1 × 1010 gC year−1, similar to the annual air–sea CO2 uptake (5.0 × 1010 gC year−1). Although the NCP and TOC loading from freshwater inputs were respectively 3.0 and 2.7 times lower than those in the 1970s, the TOC sedimentation rate was similar. Therefore, a relatively high carbon efflux from Tokyo Bay likely occurred in the 1970s, including CO2 efflux to the atmosphere and/or export of labile organic carbon to the open ocean. The changes in carbon flow between the 1970s and 2011–2012 resulted from improved water quality due to increased sewage treatment facilities and improved sewage treatment efficiency in the catchment, which decreased the amount of labile organic carbon flowing into the bay.

scholarly journals Impact of hurricanes on the flux of rainwater and Cape Fear River water dissolved organic carbon to Long Bay, southeastern United States

2004 ◽  
Vol 18 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
G. Brooks Avery ◽  
Robert J. Kieber ◽  
Joan D. Willey ◽  
G. Christopher Shank ◽  
Robert F. Whitehead
Keyword(s):  
United States ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
River Water ◽  
Southeastern United States ◽  
Long Bay ◽  
Cape Fear River ◽  
Cape Fear

scholarly journals The Impact of Anthropogenic Land-Use Change on Soil Organic Carbon, Oporae Valley, Lake Tutira, New Zealand

2021 ◽  
Author(s):  
◽  
Roderick Charles James Boys
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Land Use Change ◽  
Soil Organic Carbon ◽  
Sedimentation Rate ◽  
Large Scale ◽  
Slope Angle ◽  
Carbon Accounting ◽  
Native Forest ◽  
The Impact

<p>During the anthropocene land use change has exacerbated erosion of the Soil Organic Carbon (SOC) rich topsoil in the Oporae Valley. As well as reducing the SOC content of the contemporary topsoil, the large scale redistribution of sediment has created a quantifiable long-term SOC sink in paleosols. Using contemporary native forest soils as a proxy, pasture covered topsoils contain ~40% less SOC (a loss of 5,338 T/[square kilometer] SOC). The pre-human paleosol at ~200 cm, an average 32 cm thickness, contains 9180 T/[square kilometer]. Significantly more SOC buried at depth than what currently exists in the contemporary topsoil indicates the relative importance of paleosols as C stores and the role of land use change on SOC. The preservation characteristics of a paleosol in the Oporae Valley are determined by slope angle and the relative position they hold in relation to the inter-fingering of the alluvial toeslope with the colluvial footslope. Groupings of [radioisotope carbon-14] ages in and above the pre-human paleosol allow for calculation of terrestrial sedimentation rates. At ~0.9 mm yr^-1 the terrestrial pre-human sedimentation rate averaged over the valley floor is approximately half (0.53) of the corresponding pre-human lake rate of ~1.7 mm yr^-1. As a proportion of the lake's anthropogenic sedimentation rate at ~4.8 mm yr^-1, the terrestrial anthropogenic sedimentation rate has slightly increased to ~2.8 mm yr^-1 (0.58 of the lake sedimentation rate). These initial findings demonstrate the potential for further research in this area, so that ongoing land-use change can be accurately incorporated into terrestrial carbon accounting.</p>

scholarly journals Sedimentation rate and organic matter dynamics shape microbiomes across a continental margin

2021 ◽  
Author(s):  
Sabyasachi Bhattacharya ◽  
Tarunendu Mapder ◽  
Svetlana Fernandes ◽  
Chayan Roy ◽  
Jagannath Sarkar ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Organic Matter ◽  
Organic Carbon ◽  
Sedimentation Rate ◽  
Bottom Water ◽  
Sediment Cores ◽  
Sediment Surface ◽  
Geochemical Data ◽  
Sediment Layer ◽  
Shelf Slope

Abstract. Marine sedimentation rate and bottom-water O2 concentration control the remineralization/sequestration of organic carbon across continental margins; but whether/how they shape microbiome architecture (the ultimate effector of all biogeochemical phenomena), across shelf/slope sediments, is unknown. Here we reveal distinct microbiome structures and functions, amidst comparable pore fluid chemistries, along 300 cm sediment horizons underlying the seasonal (shallow coastal) and perennial (deep sea) oxygen minimum zones (OMZs) of the Arabian Sea, situated across the western-Indian margin (water-depths: 31 m and, 530 and 580 m, respectively). The sedimentary geomicrobiology was elucidated by analyzing metagenomes, metatranscriptomes, and enrichment cultures, and also sedimentation rates measured by radiocarbon and lead excess (210Pbxs); the findings were then evaluated in the light of the other geochemical data available for the cores investigated. Along the perennial- and seasonal-OMZ sediment cores, microbial communities were dominated by Gammaproteobacteria and Alphaproteobacteria, and Euryarchaeota and Firmicutes, respectively. As a perennial-OMZ signature, a cryptic methane production-consumption cycle was found to operate near the sediment-surface (within the sulfate reduction zone); overall diversity, as well as the relative abundances of simple-fatty-acids-requiring anaerobes (methanogens, anaerobic methane-oxidizers, sulfate-reducers and acetogens), peaked in the topmost sediment-layer and then declined via synchronized fluctuations until the sulfate-methane transition zone was reached. The entire microbiome profile was reverse in the seasonal-OMZ sediment horizon. In the perennial-OMZ sediments organic carbon deposited was higher in concentration and marine components-rich, so it potentially degraded readily to simple fatty acids; lower sedimentation rate afforded higher O2 exposure time for organic matter degradation despite perennial hypoxia in the bottom-water; thus, the resultant abundance of reduced carbon substrates sustained multiple inter-competing microbial processes in the upper sediment-layers. Remarkably, the whole geomicrobial scenario was opposite in the sediments of the seasonal/shallow-water OMZ. Our findings create a microbiological baseline for understanding carbon-sulfur cycling across distinct marine depositional settings and water-column oxygenation regimes.

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