scholarly journals Modelling carbon overconsumption and the formation of extracellular particulate organic carbon

2007 ◽  
Vol 4 (1) ◽  
pp. 13-67 ◽  
Author(s):  
M. Schartau ◽  
A. Engel ◽  
J. Schröter ◽  
S. Thoms ◽  
C. Völker ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Organic Nitrogen ◽  
Dissolved Inorganic Carbon ◽  
Inorganic Nitrogen ◽  
C:N Ratio ◽  
Algal Growth ◽  
Phytoplankton Growth ◽  
Maximum Likelihood Estimates ◽  
Model Parameters

Abstract. During phytoplankton growth a fraction of dissolved inorganic carbon (DIC) assimilated by phytoplankton is exuded in the form of dissolved organic carbon (DOC), which can be transformed into extracellular particulate organic carbon (POC). A major fraction of extracellular POC is associated with carbon of transparent exopolymer particles (TEP; carbon content = TEPC) that form from dissolved polysaccharides (PCHO). The exudation of PCHO is linked to an excessive uptake of DIC that is not directly quantifiable from utilisation of dissolved inorganic nitrogen (DIN), called carbon overconsumption. Given these conditions, the concept of assuming a constant stoichiometric carbon-to-nitrogen (C:N) ratio for estimating new production of POC from DIN uptake becomes inappropriate. Here, a model of carbon overconsumption is analysed, combining phytoplankton growth with TEPC formation. The model describes two modes of carbon overconsumption. The first mode is associated with DOC exudation during phytoplankton biomass accumulation. The second mode is decoupled from algal growth, but leads to a continuous rise in POC while particulate organic nitrogen (PON) remains constant. While including PCHO coagulation, the model goes beyond a purely physiological explanation of building up carbon rich particulate organic matter (POM). The model is validated against observations from a mesocosm study. Maximum likelihood estimates of model parameters, such as nitrogen- and carbon loss rates of phytoplankton, are determined. The optimisation yields results with higher rates for carbon exudation than for the loss of organic nitrogen. It also suggests that the PCHO fraction of exuded DOC was 63±20% during the mesocosm experiment. Optimal estimates are obtained for coagulation kernels for PCHO transformation into TEPC. Model state estimates are consistent with observations, where 30% of the POC increase was attributed to TEPC formation. The proposed model is of low complexity and is applicable for large-scale biogeochemical simulations.

scholarly journals Modelling carbon overconsumption and the formation of extracellular particulate organic carbon

2007 ◽  
Vol 4 (4) ◽  
pp. 433-454 ◽  
Author(s):  
M. Schartau ◽  
A. Engel ◽  
J. Schröter ◽  
S. Thoms ◽  
C. Völker ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Organic Nitrogen ◽  
Dissolved Inorganic Carbon ◽  
Inorganic Nitrogen ◽  
C:N Ratio ◽  
Algal Growth ◽  
Phytoplankton Growth ◽  
Maximum Likelihood Estimates ◽  
Model Parameters

Abstract. During phytoplankton growth a fraction of dissolved inorganic carbon (DIC) assimilated by phytoplankton is exuded in the form of dissolved organic carbon (DOC), which can be transformed into extracellular particulate organic carbon (POC). A major fraction of extracellular POC is associated with carbon of transparent exopolymer particles (TEP; carbon content = TEPC) that form from dissolved polysaccharides (PCHO). The exudation of PCHO is linked to an excessive uptake of DIC that is not directly quantifiable from utilisation of dissolved inorganic nitrogen (DIN), called carbon overconsumption. Given these conditions, the concept of assuming a constant stoichiometric carbon-to-nitrogen (C:N) ratio for estimating new production of POC from DIN uptake becomes inappropriate. Here, a model of carbon overconsumption is analysed, combining phytoplankton growth with TEPC formation. The model describes two modes of carbon overconsumption. The first mode is associated with DOC exudation during phytoplankton biomass accumulation. The second mode is decoupled from algal growth, but leads to a continuous rise in POC while particulate organic nitrogen (PON) remains constant. While including PCHO coagulation, the model goes beyond a purely physiological explanation of building up carbon rich particulate organic matter (POM). The model is validated against observations from a mesocosm study. Maximum likelihood estimates of model parameters, such as nitrogen- and carbon loss rates of phytoplankton, are determined. The optimisation yields results with higher rates for carbon exudation than for the loss of organic nitrogen. It also suggests that the PCHO fraction of exuded DOC was 63±20% during the mesocosm experiment. Optimal estimates are obtained for coagulation kernels for PCHO transformation into TEPC. Model state estimates are consistent with observations, where 30% of the POC increase was attributed to TEPC formation. The proposed model is of low complexity and is applicable for large-scale biogeochemical simulations.

scholarly journals Particulate organic carbon (POC) in relation to other pore water carbon fractions in drained and rewetted fens in Southern Germany

2008 ◽  
Vol 5 (6) ◽  
pp. 1615-1623 ◽  
Author(s):  
S. Fiedler ◽  
B. S. Höll ◽  
A. Freibauer ◽  
K. Stahr ◽  
M. Drösler ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Pore Water ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Relative Importance ◽  
Pore Waters ◽  
Calcareous Fens ◽  
Essential Components ◽  
The Individual

Abstract. Numerous studies have dealt with carbon (C) contents in Histosols, but there are no studies quantifying the relative importance of the individual C components in pore waters. For this study, measurements were taken of all the carbon components (particulate organic carbon, POC; dissolved organic carbon, DOC; dissolved inorganic carbon, DIC; dissolved methane, CH4) in the soil pore water of calcareous fens under three different water management regimes (re-wetted, deeply and moderately drained). Pore water was collected weekly or biweekly (April 2004 to April 2006) at depths between 10 and 150 cm. The main results obtained were: (1) DIC (94–280 mg C l−1) was the main C-component. (2) POC and DOC concentrations in the pore water (14–125 mg C l−1 vs. 41–95 mg C l−1) were pari passu. (3) Dissolved CH4 was the smallest C component (0.005–0.9 mg C l−1). Interestingly, about 30% of the POM particles were colonized by microbes indicating that they are active in the internal C turnover. Certainly, both POC and DOC fractions are essential components of the C budget of peatlands. Furthermore, dissolved CO2 in all forms of DIC appears to be an important part of peatland C-balance.

Dissolved nutrients and organic particulates in water flowing over coral reefs at Lizard Island

1983 ◽  
Vol 34 (6) ◽  
pp. 835 ◽  
Author(s):  
CJ Crossland ◽  
DJ Barnes
Keyword(s):  
Organic Carbon ◽  
Coral Reefs ◽  
Organic Nitrogen ◽  
Inorganic Nitrogen ◽  
Dissolved Nutrients ◽  
Reef Complex ◽  
Nutrient Levels ◽  
Lizard Island ◽  
Nitrogen Phosphorus ◽  
Benthic Zone

Concentrations of dissolved nutrients and organic particulates were measured in seawater flowing across the windward and leeward reef flats of the lagoonal reef complex at Lizard Island. Measurements were made during the day, at night, and at various stages of the tide over a period of several weeks. The reef complex, as a whole, did not consume or export statistically significant amounts of inorganic nitrogen, phosphorus, silicate, organic nitrogen or organic carbon. Depletion or elevation of nutrient levels in one benthic zone appeared to be balanced by production or consumption in downstream zones.

Linkage between Epilithic Algal Growth and Water Column Nutrients in Softwater Lakes

1992 ◽  
Vol 49 (8) ◽  
pp. 1641-1649 ◽  
Author(s):  
G. Winfield Fairchild ◽  
John W. Sherman
Keyword(s):  
Nutrient Limitation ◽  
Water Column ◽  
Chlorophyll A ◽  
Standing Crop ◽  
Crop Production ◽  
Dissolved Inorganic Carbon ◽  
Inorganic Nitrogen ◽  
Algal Growth ◽  
Acidic Lakes ◽  
Softwater Lakes

We examined the dependence of epilithic algal standing crop, production, and nutrient limitation upon water column nutrients in 12 softwater lakes of northeastern Pennsylvania. Elevated dissolved inorganic nitrogen accompanied low dissolved inorganic carbon in the more acidic lakes, while P varied little within the study area. The growth of epilithon on clay flower pot substrata diffusing combinations of N (NaNO3), P (Na2HPO4), and C (NaHCO3) was compared with growth on control substrata to evaluate which of the three nutrients limited growth in each lake. Standing crop accrual as chlorophyll a on control substrata averaged 0.8 μg/cm2, with little variation among lakes. Nutrient limitation of growth, however, was strongly related to lake alkalinity. Chlorophyll a was typically enhanced by N and/or P only in lakes with alkalinity greater than ~100 μeq/L and responded strongly to C enrichment in the two most acidic lakes. Combined addition of all three nutrients produced the largest chlorophyll a accrual in all 12 lakes. Invertebrate grazer biomass, dominated by chironomids in the more acidic lakes and by snails at higher alkalinity, was negatively related to chlorophyll a on these NPC substrata (r = −0.57, p = 0.05) and may have reduced algal standing crop well below nutrient-sustainable levels in some lakes.

scholarly journals The relevance of particulate organic carbon (POC) for carbon composition in the pore water of drained and rewetted fens of the "Donauried" (South-Germany)

2008 ◽  
Vol 5 (3) ◽  
pp. 2049-2073
Author(s):  
S. Fiedler ◽  
B. S. Höll ◽  
A. Freibauer ◽  
K. Stahr ◽  
M. Drösler ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Pore Water ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Relative Importance ◽  
Pore Waters ◽  
Soil C ◽  
Calcareous Fen ◽  
Essential Components

Abstract. Numerous studies have dealt with carbon (C) concentrations in Histosols, but there are no studies quantifying the relative importance of all individual C components in pore waters. For this study, measurements were made of all the carbon components (i.e., particulate organic carbon, POC; dissolved organic carbon, DOC; dissolved inorganic carbon, DIC; dissolved methane, CH4) in the soil pore water of a calcareous fen under three different water management regimes (re-wetted, deeply and moderately drained). Pore water was collected weekly or biweekly (April 2004 to April 2006) at depths between 10 and 150 cm. The main results obtained were: (1) DIC (94–280 mg C l−1) was the main C-component. (2) POC and DOC concentrations in the pore water (14–125 mg C l−1 vs. 41–95 mg C l−1) were pari passu. (3) Dissolved CH4 was the smallest C component (0.005–0.9 mg C l−1). Interestingly, about 30% of the POM particles were colonized by microbes indicating that they are active in the internal C transfer in the soil profile ("C-Shuttles"). Consequently, it was concluded that POC is at least as important as DOC for internal soil C turnover. There is no reason to assume significant biochemical differences between POC and DOC as they only differ in size. Therefore, both POC and DOC fractions are essential components of C budgets of peatlands. Furthermore dissolved CO2 in all forms of DIC apparently is an important part of peatland C-balances.

scholarly journals A mathematical modelling of bloom of the coccolithophore <i>Emiliania huxleyi</i> in a mesocosm experiment

2008 ◽  
Vol 5 (1) ◽  
pp. 787-840 ◽  
Author(s):  
P. Joassin ◽  
B. Delille ◽  
K. Soetaert ◽  
A. V. Borges ◽  
L. Chou ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dynamic Model ◽  
Dissolved Inorganic Carbon ◽  
Algal Growth ◽  
Emiliania Huxleyi ◽  
Mesocosm Experiment ◽  
Total Alkalinity ◽  
Viral Lysis ◽  
Nitrogen And Phosphorus ◽  
Biogeochemical Parameters

Abstract. A dynamic model has been developed to represent biogeochemical variables and processes observed during a bloom of Emiliania huxleyi coccolithophore. This bloom was induced in a mesocosm experiment during which the ecosystem development was followed over a period of 23-days through changes in various biogeochemical parameters such as inorganic nutrients (nitrate, ammonium and phosphate), total alkalinity (TA), dissolved inorganic carbon (DIC), partial pressure of CO2 (pCO2), dissolved oxygen (O2), photosynthetic pigments, particulate organic carbon (POC), dissolved organic carbon (DOC), Transparent Exopolymer Particles (TEP), primary production, and calcification. This dynamic model is based on unbalanced algal growth and balanced bacterial growth. In order to adequately reproduce the observations, the model includes an explicit description of phosphorus cycling, calcification, TEP production and an enhanced mortality due to viral lysis. The model represented carbon, nitrogen and phosphorus fluxes observed in the mesocosms. Modelled profiles of algal biomass and final concentrations of DIC and nutrients are in agreement with the experimental observations.

scholarly journals Bridging the gaps between particulate backscattering measurements and modeled particulate organic carbon in the ocean

2021 ◽  
Author(s):  
Martí Galí ◽  
Marcus Falls ◽  
Hervé Claustre ◽  
Olivier Aumont ◽  
Raffaele Bernardello
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Optical Data ◽  
Model Parameters ◽  
Turnover Rates ◽  
Argo Data ◽  
Dynamic Component ◽  
Argo Floats ◽  
Biogeochemical Models ◽  
Sinking Particles

Abstract. Oceanic particulate organic carbon (POC) is a relatively small (~4 Pg C) but dynamic component of the global carbon cycle with fast mean turnover rates compared to other oceanic, continental and atmospheric carbon stocks. Biogeochemical models historically focused on reproducing the sinking flux of POC driven by large fast-sinking particles (bPOC). However, suspended and slow-sinking particles (sPOC) typically represent 80–90 % of the POC stock, and can make important seasonal contributions to vertical fluxes through the mesopelagic layer (200–1000 m). Recent developments in the parameterization of POC reactivity in the PISCES model (PISCESv2_RC) have greatly improved its ability to capture sPOC dynamics. Here we evaluated this model by matching 3D and 1D simulations with BGC-Argo and satellite observations in globally representative ocean biomes, building on a refined scheme for converting particulate backscattering profiles measured by BGC-Argo floats to POC. We show that PISCES captures the major features of sPOC and bPOC as seen by BGC-Argo floats across a range of spatiotemporal scales, from highly resolved profile time series to biome-aggregated climatological profiles. Our results also illustrate how the comparison between the model and observations is hampered by (1) the uncertainties in empirical POC estimation, (2) the imperfect correspondence between modelled and observed variables, and (3) the bias between modelled and observed physics. Despite these limitations, we identified characteristic patterns of model-observations misfits in the mesopelagic layer of subpolar and subtropical gyres. These misfits likely result from both suboptimal model parameters and model equations themselves, pointing to the need to improve the model representation of processes with a critical influence on POC dynamics, such as sinking, remineralization, (dis)aggregation and zooplankton activity. Beyond model evaluation results, our analysis identified inconsistencies between current estimates of POC from satellite and BGC-Argo data, as well as POC partitioning into phytoplankton, heterotrophs and detritus deduced from in situ bio-optical data. Our approach can help constrain POC stocks, and ultimately budgets, in the epipelagic and mesopelagic ocean.

Proteins: Amino Acids and Amines

2011 ◽  
Author(s):  
Thomas S. Bianchi ◽  
Elizabeth A. Canuel
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Particulate Organic Carbon ◽  
Nitrogen Cycle ◽  
Organic Nitrogen ◽  
Building Blocks ◽  
Marine Organisms ◽  
Carbon And Nitrogen

This chapter discusses proteins, which make up approximately 50% of organic matter and contain about 85% of the organic nitrogen in marine organisms. Peptides and proteins comprise an important fraction of the particulate organic carbon (13–37%) and particulate organic nitrogen (30–81%), as well as dissolved organic nitrogen (5–20%) and dissolved organic carbon (3–4%) in oceanic and coastal waters. In sediments, proteins account for approximately 7 to 25% of organic carbon and an estimated 30 to 90% of total nitrogen. Amino acids are the basic building blocks of proteins. This class of compounds is essential to all organisms and represents one of the most important components in the organic nitrogen cycle. Amino acids represent one of the most labile pools of organic carbon and nitrogen.

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

2012 ◽  
Vol 9 (6) ◽  
pp. 2045-2062 ◽  
Author(s):  
S. Bouillon ◽  
A. Yambélé ◽  
R. G. M. Spencer ◽  
D. P. Gillikin ◽  
P. J. Hernes ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Seasonal Variations ◽  
Dissolved Inorganic Carbon ◽  
Low Flow ◽  
Tropical Rivers ◽  
Particulate Nitrogen ◽  
Congo River

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. δ13C signatures of both POC and DOC showed strong seasonal variations (−30.6 to −25.8‰, and −31.8 to −27.1‰, respectively), but their different timing indicates that the origins of POC and DOC may vary strongly over the hydrograph and are largely uncoupled, differing up to 6‰ in δ13C signatures. 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, consistent with major seasonal variations in the sources of dissolved organic matter. 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. The low POC/PN ratios, high %POC and low and variable δ13CPOC signatures during low flow conditions suggest that the majority of the POC pool during this period consists of in situ produced phytoplankton, consistent with concurrent pCO2 (partial pressure of CO2) values only slightly above and, occasionally, below atmospheric equilibrium. Water-atmosphere CO2 fluxes estimated using two independent approaches averaged 105 and 204 g C m−2 yr−1, i.e. more than an order of magnitude lower than current estimates for large tropical rivers globally. 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. The total annual flux of TSM, POC, PN, DOC and DIC are 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. 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.

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