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.

Small-Scale Gradients in Big River: Implications for a State-of-the-Art Research Platform in the Elbe

2021 ◽  
Author(s):  
Sina Bold ◽  
Justus E.E. van Beusekom ◽  
Yoana G. Voynova ◽  
Marius Cysewski ◽  
Bryce Van Dam ◽  
...  
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Ammonium Phosphate ◽  
Total Alkalinity ◽  
Small Scale ◽  
Suspended Particulate ◽  
Research Platform ◽  
Biogeochemical Parameters ◽  
Art Research ◽  
Set Up

&lt;p&gt;Estuaries are crucial in transforming matter fluxes from land to sea. To better understand and quantify these processes and respective fluxes, it is important to determine the input into an estuary accurately. To allow for such studies in the Elbe estuary in Germany, a state-of-the-art research platform is currently being set-up just upstream of the weir in Geesthacht at the entrance of the estuary. Here, we report on small-scale spatial dynamics of organic matter and associated processes from several cross and longitudinal profiles around the planned location and the implications for the set-up of the aforementioned research platform.&lt;/p&gt;&lt;p&gt;Based on preliminary data obtained in August 2020 during a period of relatively low discharge, we present the following results: (1) In three cross profiles along a 10 km transect of the Elbe upstream of the weir, we observed considerable small-scale gradients regarding currents and various biogeochemical parameters. In comparison to the fairway, water from the riverbanks was depleted in suspended particulate matter, chlorophyll a, dissolved oxygen, and nitrate, and enhanced in ammonium, phosphate and silicate, as well as total alkalinity and dissolved inorganic carbon paralleled by decreasing pH. This suggests that in the summer, organic matter is deposited and remineralised at the riverbanks, resulting in the release of ammonium, phosphate and silicate, and in the removal of nitrate, presumably by denitrification. (2) Along the 10 km transect towards the weir, we observed that concentrations of suspended particulate matter, chlorophyll a, dissolved oxygen, nitrate and pH were decreasing. In contrast, we found that ammonium, phosphate and silicate, total alkalinity and dissolved inorganic carbon increased towards the weir. This suggests an increased sedimentation and subsequent remineralisation due to the reduced flow velocities in front of the weir. (3) An analysis of a 10-year time series from the weir supports this by showing higher ammonium concentrations when discharges were relatively low. The implications of these findings for the set-up of the research platform in this area, as well as for optimising estimates of budgets are discussed. The research platform will contribute to understand further such variations in biogeochemical parameters at the entrance of the Elbe estuary over time.&lt;/p&gt;&lt;p&gt;The research platform is set-up in cooperation with the Helmholtz initiative MOSES (&amp;#8220;Modular Observation Solutions for Earth Systems&amp;#8220;) and will be incorporated in the Elbe-North Sea Supersite of DANUBIUS-RI (&amp;#8220;International Centre for Advanced Studies on River-Sea Systems&amp;#8220;). Funding is provided by European Regional Development Funds, the federal state of Schleswig-Holstein, the Helmholtz Association and the Helmholtz-Zentrum Geesthacht. The research platform, planned to be operational in autumn 2021, will also be open for users e.g. to develop and test new methods and technologies. Data will be made available through the &amp;#8220;Helmholtz Coastal Data Centre&amp;#8221; (HCDC).&lt;/p&gt;

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 Winter measurements of biogeochemical parameters in the Rockall Trough (2009–2012)

2013 ◽  
Vol 6 (2) ◽  
pp. 389-409
Author(s):  
T. McGrath ◽  
C. Kivimäe ◽  
E. McGovern ◽  
R. R. Cave ◽  
E. Joyce
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Total Alkalinity ◽  
Dissolved Inorganic Nutrients ◽  
Chemical Signatures ◽  
Rockall Trough ◽  
Biogeochemical Parameters ◽  
Oxidised Nitrogen

Abstract. This paper describes the sampling and analysis of biogeochemical parameters collected in the Rockall Trough in January/February of 2009, 2010, 2011 and 2012. Sampling was carried out across two transects, one southern and one northern transect each year. Samples for dissolved inorganic carbon (DIC) and total alkalinity (TA) were taken alongside salinity, dissolved oxygen and dissolved inorganic nutrients (total-oxidised nitrogen, nitrite, phosphate and silicate) to describe the chemical signatures of the various water masses in the region. These were taken at regular intervals through the water column. The 2009 and 2010 data are available on the CDIAC database.

scholarly journals Macroalgal metabolism and lateral carbon flows can create significant carbon sinks

2020 ◽  
Vol 17 (9) ◽  
pp. 2425-2440 ◽  
Author(s):  
Kenta Watanabe ◽  
Goro Yoshida ◽  
Masakazu Hori ◽  
Yu Umezawa ◽  
Hirotada Moki ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Water Exchange ◽  
Dissolved Inorganic Carbon ◽  
Field Measurements ◽  
High Water ◽  
Co2 Exchange ◽  
Atmospheric Co2 ◽  
Total Alkalinity ◽  
Co2 Uptake ◽  
Offshore Area

Abstract. Macroalgal beds have drawn attention as one of the vegetated coastal ecosystems that act as atmospheric CO2 sinks. Although macroalgal metabolism as well as inorganic and organic carbon flows are important pathways for CO2 uptake by macroalgal beds, the relationships between macroalgal metabolism and associated carbon flows are still poorly understood. In the present study, we investigated carbon flows, including air–water CO2 exchange and budgets of dissolved inorganic carbon, total alkalinity, and dissolved organic carbon (DOC), in a temperate macroalgal bed during the productive months of the year. To assess the key mechanisms responsible for atmospheric CO2 uptake by the macroalgal bed, we estimated macroalgal metabolism and lateral carbon flows (i.e., carbon exchanges between the macroalgal bed and the offshore area) by using field measurements of carbon species, a field-bag method, a degradation experiment, and mass-balance modeling in a temperate Sargassum bed over a diurnal cycle. Our results showed that macroalgal metabolism and lateral carbon flows driven by water exchange affected air–water CO2 exchange in the macroalgal bed and the surrounding waters. Macroalgal metabolism caused overlying waters to contain low concentrations of CO2 and high concentrations of DOC that were efficiently exported offshore from the macroalgal bed. These results indicate that the exported water can potentially lower CO2 concentrations in the offshore surface water and enhance atmospheric CO2 uptake. Furthermore, the Sargassum bed exported 6 %–35 % of the macroalgal net community production (NCP; 302–1378 mmol C m−2 d−1) as DOC to the offshore area. The results of degradation experiments showed that 56 %–78 % of macroalgal DOC was refractory DOC (RDOC) that persisted for 150 d; thus, the Sargassum bed exported 5 %–20 % of the macroalgal NCP as RDOC. Our findings suggest that macroalgal beds in habitats associated with high water exchange rates can create significant CO2 sinks around them and export a substantial amount of DOC to offshore areas.

scholarly journals Apports En Carbone Et Azote Dans Le Fleuve Niger À Tondibia (Niamey) : Résultats De Deux (2) Ans D’observations

2016 ◽  
Vol 12 (21) ◽  
pp. 167
Author(s):  
Alhou B ◽  
Issiaka Boukari ◽  
Darchambeau F.
Keyword(s):  
Organic Carbon ◽  
Suspended Matter ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
First Year ◽  
Nitrogen And Phosphorus ◽  
Temperature Conductivity ◽  
Continental Scale ◽  
The Mean ◽  
Hydrographic Regions

The Niger River is the third more important river in Africa and drains a surface of about 2,120,000 km². It includes six hydrographic regions representing West African ecosystems. Despite the importance of this river at the regional and continental scale, little information has been collected on its biogeochemical characteristics and particularly on its role in the transportation and the transformation of matter (carbon, nitrogen and phosphorus). This study present the results of two years investigation, April 2011 to March 2013 in the middle Niger, upstream Niamey (Niger) city [2.01° E, 13.57° N], according to a bi-weekly observation frequency. The variables measured are temperature, conductivity, dissolved oxygen, pH, suspended matter, dissolved inorganic carbon (C) and nitrogen (N) and particulars organics C and N as well as isotopic composition of these elements. Daily discharges of the river come from hydrologic station measurement of the Niger authority Basin (NBA) at Niamey city. Hydrologic situation was strongly contrasted between the 2 years of survey. The mean discharge of the first year was only 673 m3 s-1 (one of the weakest discharge recorded on the river Niger at Niamey since 1940), while the mean discharge of the second year was 1,096 m3 s-1. Our results show that suspended matter, particular organic carbon, dissolved organic carbon and dissolved inorganic carbon are transported mainly during the local flood, induced by precipitations in July and August. The second flood (Guinean flood) which occurred, during November to January, is characterized by low temperatures and clean waters.

scholarly journals Winter measurements of oceanic biogeochemical parameters in the Rockall Trough (2009–2012)

2013 ◽  
Vol 5 (2) ◽  
pp. 375-383 ◽  
Author(s):  
T. McGrath ◽  
C. Kivimäe ◽  
E. McGovern ◽  
R. R. Cave ◽  
E. Joyce
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Inorganic Nutrients ◽  
Total Alkalinity ◽  
Dissolved Inorganic Nutrients ◽  
Chemical Signatures ◽  
Rockall Trough ◽  
Biogeochemical Parameters

Abstract. This paper describes the sampling and analysis of biogeochemical parameters collected in the Rockall Trough in January/February of 2009, 2010, 2011 and 2012. Sampling was carried out along two transects, one southern and one northern transect each year. Samples for dissolved inorganic carbon (DIC) and total alkalinity (TA) were taken alongside salinity, dissolved oxygen and dissolved inorganic nutrients (total-oxidized nitrogen, nitrite, phosphate and silicate) to describe the chemical signatures of the various water masses in the region. These were taken at regular intervals through the water column. The data are available on the CDIAC database, http://cdiac.ornl.gov/ftp/oceans/Rockall_Trough/.

scholarly journals Macroalgal metabolism and lateral carbon flows create extended atmospheric CO<sub>2</sub> sinks

2019 ◽  
Author(s):  
Kenta Watanabe ◽  
Goro Yoshida ◽  
Masakazu Hori ◽  
Yu Umezawa ◽  
Hirotada Moki ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Co2 Sequestration ◽  
Water Exchange ◽  
Dissolved Inorganic Carbon ◽  
High Water ◽  
Co2 Exchange ◽  
Atmospheric Co2 ◽  
Total Alkalinity ◽  
Co2 Uptake ◽  
High Concentrations

Abstract. Macroalgal beds have drawn attention as one of the vegetated coastal ecosystems that act as atmospheric CO2 sinks. Although macroalgal metabolism as well as inorganic and organic carbon flows are important pathways for CO2 sequestration by macroalgal beds, the relationships between macroalgal metabolism and associated carbon flows are still poorly understood. In the present study, we investigated carbon flows, including air–water CO2 exchange and budgets of dissolved inorganic carbon, total alkalinity, and dissolved organic carbon (DOC) in a temperate macroalgal bed during productive months of the year. To assess the key mechanisms of CO2 sequestration by the macroalgal bed, we estimated macroalgal metabolism and lateral carbon flows using a field-bag method, a degradation experiment, and mass balance modelling over a diurnal cycle. Our results showed that macroalgal metabolism and lateral carbon flows driven by water exchange affected air–water CO2 exchange in the macroalgal bed and the surrounding waters. Macroalgal metabolism caused overlying waters to contain low concentrations of CO2 and high concentrations of DOC that were efficiently exported offshore from the macroalgal bed. The exported water lowered CO2 concentrations in the offsite surface water and enhanced atmospheric CO2 uptake. Our findings suggest that macroalgal beds in habitats associated with high water exchange rates can create extensive CO2-sinks around them.

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.

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