Transformation of dissolved inorganic carbon (DIC) into particulate organic carbon (POC) in the lower Xijiang River, SE China: an isotopic approach

2011 ◽  
Vol 8 (5) ◽  
pp. 9471-9501 ◽  
Author(s):  
H. G. Sun ◽  
J. T. Han ◽  
S. R. Zhang ◽  
X. X. Lu
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Rainy Season ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
Dry Season ◽  
Study Region ◽  
Carbon Isotopic ◽  
Xijiang River ◽  
Extreme Flood

Abstract. The sources and dynamics of riverine carbon have been discussed extensively, but knowledge about the transformation from DIC into organic carbon (OC) is still poorly understood. In this study, we conducted a comprehensive investigation on the riverine carbon, stable carbon isotopic components and C/N ratios for different seasons, including an extreme flood event, in the lower Xijiang and its three tributaries. Detailed analyses are also performed for soil samples across the study region. Downstream increase in δ13CDIC and downstream decrease in both δ13CPOC and C/N have been observed for all the tributaries. Meanwhile, positive shift of δ13CDIC and negative shift of δ13CPOC are also observed from summer to winter. These observations likely indicate that the isotopic compositions of both DIC and POC are significantly affected by in-river primary production that converts DIC into organic matter through photosynthesis. It is estimated that the percentage contribution of the riverine aquatic primary production to the riverine POC in the Xijiang and three tributaries of Guijiang, Hejiang and Luoding is respectively 7.1%, 43.2%, 36.4% and 9.9% in rainy season, and 35.6%, 47.3%, 50.3% and 40.1% in dry season. Based on the stoichiometry involved in chemical weathering of the bedrocks, the transformation of the carbonate-sourced DIC to POC is further quantified to be 3.4–20.5% in rainy season, and 12.3–22.1% in dry season. This may suggest an important sink of atmospheric CO2 in river systems that was largely ignored previously.

scholarly journals Carbon Balance in Salt Marsh and Mangrove Ecosystems: A Global Synthesis

2020 ◽  
Vol 8 (10) ◽  
pp. 767 ◽  
Author(s):  
Daniel M. Alongi
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Salt Marshes ◽  
Dissolved Inorganic Carbon ◽  
Net Primary Production ◽  
Ecosystem Respiration ◽  
Soil Depth ◽  
Gross Primary Production ◽  
Coastal Ocean ◽  
Microbial Decomposition

Mangroves and salt marshes are among the most productive ecosystems in the global coastal ocean. Mangroves store more carbon (739 Mg CORG ha−1) than salt marshes (334 Mg CORG ha−1), but the latter sequester proportionally more (24%) net primary production (NPP) than mangroves (12%). Mangroves exhibit greater rates of gross primary production (GPP), aboveground net primary production (AGNPP) and plant respiration (RC), with higher PGPP/RC ratios, but salt marshes exhibit greater rates of below-ground NPP (BGNPP). Mangroves have greater rates of subsurface DIC production and, unlike salt marshes, exhibit active microbial decomposition to a soil depth of 1 m. Salt marshes release more CH4 from soil and creek waters and export more dissolved CH4, but mangroves release more CO2 from tidal waters and export greater amounts of particulate organic carbon (POC), dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC), to adjacent waters. Both ecosystems contribute only a small proportion of GPP, RE (ecosystem respiration) and NEP (net ecosystem production) to the global coastal ocean due to their small global area, but contribute 72% of air–sea CO2 exchange of the world’s wetlands and estuaries and contribute 34% of DIC export and 17% of DOC + POC export to the world’s coastal ocean. Thus, both wetland ecosystems contribute disproportionately to carbon flow of the global coastal ocean.

scholarly journals ANALYSIS OF THE SEASONAL IMPACT ON ISOTOPIC BASELINES OF DISSOLVED INORGANIC CARBON (DIC) IN COASTAL WATERS SPERMONDE, SOUTH SULAWESI

2019 ◽  
Vol 11 (1) ◽  
pp. 141-149
Author(s):  
Wa Ode Rustiah ◽  
Alfian Noor ◽  
. Maming ◽  
Muhammad Lukman
Keyword(s):  
Stable Carbon Isotopes ◽  
Environmental Changes ◽  
Dissolved Inorganic Carbon ◽  
Co2 Storage ◽  
Dry Season ◽  
Inorganic Materials ◽  
Stable Carbon ◽  
Wet Season ◽  
Carbon Isotopic ◽  
South Sulawesi

Stable carbon isotopes have been commonly used as indicators for assessing environmental changes in aquatic ecosystems. They can be used to study the dynamics of organic matter as for understanding the overall functioning of the ecosystem, the connectivity of estuaries with terrestrial and marine coastal habitats. The objective of this study is determining the seasonal natural effects over isotopic (13C/12C) baselines in monitoring CO2 storage in dissolved inorganic materials in Spermonde waters on the west coast of South Sulawesi to some outermost island. The results show that the stable carbon isotopic of DIC (d13C-DIC) in the wet season varied between -5.36 ‰ and -7.74 ‰. These value are higher than on dry season (-4.34 ‰ to -6.82 ‰). Likewise, DIC concentration in the rainy season ranged between 9.5 mg C/L and 11.7 mg C/L, while in the dry season it varied from 8.5 mg C/L to 9.3 mg C/L. The d13C-DIC and DIC concentrations decreased towards offshore, up to some of the outer islands. Increasing in the d13C-DIC in Spermonde waters indicate that the DIC is most likely enriched by atmospheric CO2(g), which is outnumbered those of aquatic photosynthesis. This study shows that different levels and composition of d13C-DIC stretch along different rivers are attributable to the varying landscapes and quality of organic matters.

scholarly journals Biogeochemistry of a large and deep tropical lake (Lake Kivu, East Africa: insights from a stable isotope study covering an annual cycle

2015 ◽  
Vol 12 (16) ◽  
pp. 4953-4963 ◽  
Author(s):  
C. Morana ◽  
F. Darchambeau ◽  
F. A. E. Roland ◽  
A. V. Borges ◽  
F. Muvundja ◽  
...  
Keyword(s):  
Stable Isotope ◽  
East Africa ◽  
Seasonal Variability ◽  
Rainy Season ◽  
Dissolved Inorganic Carbon ◽  
Dry Season ◽  
Tropical Lake ◽  
Particulate Nitrogen ◽  
Δ13c And Δ15n ◽  
Lake Kivu

Abstract. During this study, we investigated the seasonal variability of the concentration and the stable isotope composition of several inorganic and organic matter (OM) reservoirs in the large, oligotrophic and deep tropical Lake Kivu (East Africa). Data were acquired over 1 year at a fortnightly temporal resolution. The δ13C signature of the dissolved inorganic carbon (DIC) increased linearly with time during the rainy season, then suddenly decreased during the dry season due to vertical mixing with 13C-depleted DIC waters. The δ13C signature of the particulate organic carbon pool (POC) revealed the presence of a consistently abundant methanotrophic biomass in the oxycline throughout the year. We also noticed a seasonal shift during the dry season toward higher values in the δ15N of particulate nitrogen (PN) in the mixed layer and δ15N-PN was significantly related to the contribution of cyanobacteria to the phytoplankton assemblage, suggesting that rainy season conditions could be more favourable to atmospheric nitrogen-fixing cyanobacteria. Finally, zooplankton were slightly enriched in 13C compared to the autochthonous POC pool, and the δ15N signature of zooplankton followed well the seasonal variability in δ15N-PN, consistently 3.0 ± 1.1 ‰ heavier than the PN pool. Together, δ13C and δ15N analysis suggests that zooplankton directly incorporate algal-derived OM in their biomass, and that they rely almost exclusively on this source of OM throughout the year in general agreement with the very low allochthonous OM inputs from rivers in Lake Kivu.

Changes in productivity associated with algal-microbial shifts during the Early Triassic recovery of marine ecosystems

2020 ◽  
Vol 133 (1-2) ◽  
pp. 362-378
Author(s):  
Yong Du ◽  
Huyue Song ◽  
Jinnan Tong ◽  
Thomas J. Algeo ◽  
Zhe Li ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Lower Triassic ◽  
Marine Ecosystems ◽  
N Fixation ◽  
Early Triassic ◽  
Carbon Isotopic ◽  
Carbonate Carbon ◽  
Composite Section ◽  
Algal Productivity

Abstract The recovery of marine ecosystems in the aftermath of the Permian-Triassic mass extinction was accompanied by significant carbon-cycle perturbations, as reflected in large-amplitude global excursions in Lower Triassic carbonate carbon isotope records. In the present study, we generated paired carbonate carbon (δ13Ccarb), organic carbon (δ13Corg), and nitrogen (δ15N) isotope records along with molar C/N ratios for a composite section in the Chaohu area of Anhui Province (northern Yangtze Platform, South China) that spans the entire Lower Triassic. These records document concurrent changes among multiple proxies related to marine plankton community composition, productivity rates, and nutricline structure, providing unparalleled insights into changes at the base of the marine trophic web during the Early Triassic recovery interval. Changes in carbonate-organic carbon isotopic differences (Δ13Ccarb-org) and C/N ratios indicate a general shift from anoxygenic photoautotrophy to eukaryotic algal productivity during the Early Triassic. The prevalence of prokaryotic photoautotrophs in the Griesbachian to Smithian was due to frequent environmental disturbance, whereas the reestablishment of eukaryotic algae as dominant primary producers in the Spathian reflects a general amelioration of marine environments at that time. Positive δ13Ccarb excursions and brief spikes toward higher Δ13Ccarb-org and C/N ratios around the Induan-Olenekian boundary and Smithian-Spathian boundary record transient shifts toward improved conditions and temporary rebounds of algal productivity. A negative δ15N shift was associated with decreasing δ13Ccarb, indicating that marine productivity was closely linked to N-fixation intensity owing to a general nutrient-N deficiency. Synchronous fluctuations of δ13Ccarb and δ13Corg through the Olenekian reflect changes in the δ13C of oceanic dissolved inorganic carbon, but the more limited variation in δ13Corg may have been due to concurrent changes in algal-microbial assemblages and, thus, net photosynthetic fractionation of carbon isotopes.

scholarly journals A <sup>13</sup>C labelling study on carbon fluxes in Arctic plankton communities under elevated CO<sub>2</sub> levels

2013 ◽  
Vol 10 (3) ◽  
pp. 1425-1440 ◽  
Author(s):  
A. de Kluijver ◽  
K. Soetaert ◽  
J. Czerny ◽  
K. G. Schulz ◽  
T. Boxhammer ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Dissolved Inorganic Carbon ◽  
Carbon Fluxes ◽  
Sediment Traps ◽  
Plankton Community ◽  
Nutrient Addition ◽  
Production Rates ◽  
Plankton Community Structure ◽  
Plankton Communities

Abstract. The effect of CO2 on carbon fluxes (production, consumption, and export) in Arctic plankton communities was investigated during the 2010 EPOCA (European project on Ocean Acidification) mesocosm study off Ny Ålesund, Svalbard. 13C labelled bicarbonate was added to nine mesocosms with a range in pCO2 (185 to 1420 μatm) to follow the transfer of carbon from dissolved inorganic carbon (DIC) into phytoplankton, bacterial and zooplankton consumers, and export. A nutrient–phytoplankton–zooplankton–detritus model amended with 13C dynamics was constructed and fitted to the data to quantify uptake rates and carbon fluxes in the plankton community. The plankton community structure was characteristic for a post-bloom situation and retention food web and showed high bacterial production (∼31% of primary production), high abundance of mixotrophic phytoplankton, low mesozooplankton grazing (∼6% of primary production) and low export (∼7% of primary production). Zooplankton grazing and export of detritus were sensitive to CO2: grazing decreased and export increased with increasing pCO2. Nutrient addition halfway through the experiment increased the export, but not the production rates. Although mixotrophs showed initially higher production rates with increasing CO2, the overall production of POC (particulate organic carbon) after nutrient addition decreased with increasing CO2. Interestingly, and contrary to the low nutrient situation, much more material settled down in the sediment traps at low CO2. The observed CO2 related effects potentially alter future organic carbon flows and export, with possible consequences for the efficiency of the biological pump.

scholarly journals Modification of Topsoil Physico-Chemical Characteristics and Macroinvertebrates Structure Consecutive to the Conversion of Secondary Forests into Rubber Plantations in Grand-Lahou, Côte d’Ivoire

2018 ◽  
Vol 8 ◽  
pp. 1235-1255
Author(s):  
N'dri Kouadio Julien ◽  
Kévin Kouadio N’Guessan
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Rainy Season ◽  
Secondary Forest ◽  
Dry Season ◽  
Chemical Characteristics ◽  
Secondary Forests ◽  
Rubber Plantations ◽  
Physico Chemical ◽  
Soil Macroinvertebrates

The objective of this investigation was to assess the modifications of topsoil physico-chemical characteristics and macroinvertebrates structure consecutive to the conversion of secondary forests into rubber plantations and how these change with the aging of the plantations and the season. The sampling design was constituted of four treatments: secondary forest referred to as baseline land use, 7-, 12- and 25 year old rubber plantations. Three replications per land use type were randomly established in each of the selected treatments, thus totaling 12 sampling areas. On each sampling area, a 40 m transect was established. The litter dwelling and topsoil (0-10 cm) macroinvertebrates were sampled, respectively, by using the pitfall traps and monoliths (50 cm × 50 cm × 10 cm) following the Tropical Soil Biology and Fertility method. The soil physical and chemical parameters were measured along the 40 m transect. The results showed that the conversion of secondary forest into plantations was characterized by a modification of the density of soil macroinvertebrates (dry season: -50 and -24% vs. rainy season: -61 and +32%), taxonomic richness of soil macroinvertebrates (dry season: +7 and -14% vs. rainy season: -21 and -14%), water content (dry season: -41 and -5% vs. rainy season: -62 and -31%), bulk density (dry season: +6 and -3% vs. rainy season: +33 and +29%), soil organic carbon (dry season: -73 and -59% vs. rainy season: -67 and -51%) and total nitrogen (dry season: -68 and -58% vs. rainy season: -64 and -52%), respectively, after about 7 and 25 years of conversion. The restoration processes did not cause significant changes in the soil physico-chemical and biological characteristics after 25 years of forests conversion. However, the study highlighted the improvement in the soil ecological quality due to a reduction in soil degradation, and an increase in the density of macroinvertebrates (+235%), taxono mic richness (+9%), water content (+84%), soil organic carbon (+50%) and total nitrogen (+33%) in the 25 year old plantations compared to the 7 year old plantations.

scholarly journals Organic matter sources, fluxes and greenhouse gas exchange in the Oubangui River (Congo River basin)

2012 ◽  
Vol 9 (1) ◽  
pp. 63-108 ◽  
Author(s):  
S. Bouillon ◽  
A. Yambélé ◽  
R. G. M. Spencer ◽  
D. P. Gillikin ◽  
P. J. Hernes ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
Low Flow ◽  
Tropical Rivers ◽  
Particulate Nitrogen ◽  
Congo River ◽  
Sampling Campaign

Abstract. The Oubangui is a major tributary of the Congo River, draining an area of ~ 500 000 km2 mainly consisting of wooded savannahs. Here, we report results of a one year long 2-weekly sampling campaign in Bangui (Central African Republic) since March 2010 for a suite of physico-chemical and biogeochemical characteristics, including total suspended matter (TSM), bulk concentration and stable isotope composition of particulate organic carbon (POC and δ13CPOC), particulate nitrogen (PN and δ15NPN), dissolved organic carbon (DOC and δ13CDOC), dissolved inorganic carbon (DIC and δ13CDIC), dissolved greenhouse gases (CO2, CH4 and N2O), and dissolved lignin composition. We estimated the total annual flux of TSM, POC, PN, DOC and DIC to be 2.33 Tg yr−1, 0.14 Tg C yr−1, 0.014 Tg N yr−1, 0.70 Tg C yr−1, and 0.49 Tg C yr−1, respectively. Most elements showed clear hysteresis over the hydrograph. δ13C signatures of both POC and DOC showed strong seasonal variations (−30.6 to −25.8 ‰, and −31.8 to −27.1 ‰, respectively) but with contrasting patterns. Our data indicate that the origins of POC and DOC may vary strongly over the hydrograph and are largely uncoupled, differing up to 6 ‰ in δ13C signatures. The low POC/PN ratios, high % POC and low and variable δ13CPOC signatures during low flow conditions suggest that during this period, the majority of the POC pool consists of in situ produced phytoplankton, consistent with concurrent pCO2 (partial pressure of CO2) values only slightly above and occasionally, below, atmospheric equilibrium. Dissolved lignin characteristics (carbon-normalised yields, cinnamyl:vanillyl phenol ratios, and vanillic acid to vanillin ratios) showed marked differences between high and low discharge conditions. We observed a~strong seasonality in pCO2, ranging between 470 ± 203 ppm for Q<1000 m3 s−1 (n=10) to a maximum of 3750 ppm during the first stage of the rising discharge. Water-atmosphere CO2 fluxes were estimated to average ~ 105 g C m−2 yr−1, i.e. more than an order of magnitude lower than current estimates for large tropical rivers globally. While our TSM and POC fluxes are similar to previous estimates for the Oubangui, DOC fluxes were ~ 30 % higher and bicarbonate fluxes were ~ 35 % lower than previous reports. DIC represented 58 % of the total annual C flux, and under the assumptions that carbonate weathering represents 25 % of the DIC flux and that CO2 from respiration drives chemical weathering, this flux is equivalent to ~ 50 % of terrestrial-derived riverine C transport. Although tropical rivers are often assumed to show much higher CO2 effluxes compared to temperate systems, we show that in situ production may be high enough to dominate the particulate organic carbon pool, and lower pCO2 values to near equilibrium values during low discharge conditions.

scholarly journals A diurnal carbon engine explains 13C-enriched carbonates without increasing the global production of oxygen

2019 ◽  
Vol 116 (49) ◽  
pp. 24433-24439 ◽  
Author(s):  
Emily C. Geyman ◽  
Adam C. Maloof
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Shallow Water ◽  
Dissolved Inorganic Carbon ◽  
The Past ◽  
Carbon Isotopic ◽  
Oxygen Paradox ◽  
Carbon Burial ◽  
Continental Shelves ◽  
Organic Carbon Burial

In the past 3 billion years, significant volumes of carbonate with high carbon-isotopic (δ13C) values accumulated on shallow continental shelves. These deposits frequently are interpreted as records of elevated global organic carbon burial. However, through the stoichiometry of primary production, organic carbon burial releases a proportional amount of O2, predicting unrealistic rises in atmospheric pO2 during the 1 to 100 million year-long positive δ13C excursions that punctuate the geological record. This carbon–oxygen paradox assumes that the δ13C of shallow water carbonates reflects the δ13C of global seawater-dissolved inorganic carbon (DIC). However, the δ13C of modern shallow-water carbonate sediment is higher than expected for calcite or aragonite precipitating from seawater. We explain elevated δ13C in shallow carbonates with a diurnal carbon cycle engine, where daily transfer of carbon between organic and inorganic reservoirs forces coupled changes in carbonate saturation (ΩA) and δ13C of DIC. This engine maintains a carbon-cycle hysteresis that is most amplified in shallow, sluggishly mixed waters with high rates of photosynthesis, and provides a simple mechanism for the observed δ13C-decoupling between global seawater DIC and shallow carbonate, without burying organic matter or generating O2.

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