scholarly journals The microbial carbon pump and the oceanic recalcitrant dissolved organic matter pool

2011 ◽  
Vol 9 (7) ◽  
pp. 555-555 ◽  
Author(s):  
Nianzhi Jiao ◽  
Gerhard J. Herndl ◽  
Dennis A. Hansell ◽  
Ronald Benner ◽  
Gerhard Kattner ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Carbon Pump ◽  
Organic Matter Pool ◽  
Microbial Carbon ◽  
Microbial Carbon Pump

scholarly journals Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean

2014 ◽  
Vol 11 (10) ◽  
pp. 14097-14132 ◽  
Author(s):  
L. Tremblay ◽  
J. Caparros ◽  
K. Leblanc ◽  
I. Obernosterer
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Southern Ocean ◽  
Surface Waters ◽  
Bacterial Degradation ◽  
Natural Iron ◽  
Average Proportion ◽  
Carbon Pump ◽  
Microbial Carbon

Abstract. Natural iron fertilization of high-nutrient low-chlorophyll (HNLC) waters induces annually occurring spring phytoplankton blooms off Kerguelen Islands (Southern Ocean). To examine the origin and fate of particulate and dissolved organic matter (POM and DOM), D- and L-amino acids (AA) were quantified at bloom and HNLC stations. Total hydrolysable AA accounted for 21–25% of surface particulate organic carbon (%POCAA) at the bloom sites, but for 10% at the HNLC site. A marked decrease in %POCAA with depth was observed at the most productive stations leading to values between 3 and 5% below 300 m depth. AA contributed to only 0.9–4.4% of dissolved organic carbon (%DOCAA) at all stations. The only consistent vertical trend was observed at the most productive station (A3-2) where %DOCAA decreased from ∼2% in the surface waters to 0.9% near 300 m. These AA yields and other markers revealed that POM and DOM were more rapidly altered or mineralized at the bloom sites compared to the HNLC site. Different molecular markers indicated that POM mostly originated from diatoms and bacteria. The estimated average proportion of POM from intact phytoplankton cells in surface waters was 45% at the bloom station A3-2, but 14% at the HNLC site. Estimates based on D-AA yields indicated that ∼15% of POM and ∼30% of DOM was of bacterial origin (cells and cell fragments) at all stations. Surprisingly, the DOM in HNLC waters appeared less altered than the DOM from the bloom, had slightly higher dissolved AA concentrations, and showed no sign of alteration within the water column. Unfavorable conditions for bacterial degradation in HNLC regions can explain these findings. In contrast, large inputs of labile organic molecules and iron, likely stimulate the degradation of organic matter (priming effect) and the production of more recalcitrant DOM (microbial carbon pump) during iron-fertilized blooms.

scholarly journals Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean

2015 ◽  
Vol 12 (2) ◽  
pp. 607-621 ◽  
Author(s):  
L. Tremblay ◽  
J. Caparros ◽  
K. Leblanc ◽  
I. Obernosterer
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Southern Ocean ◽  
Surface Waters ◽  
Bacterial Degradation ◽  
Natural Iron ◽  
Average Proportion ◽  
Carbon Pump ◽  
Microbial Carbon

Abstract. Natural iron fertilization of high-nutrient low-chlorophyll (HNLC) waters induces annually occurring spring phytoplankton blooms off the Kerguelen Islands (Southern Ocean). To examine the origin and fate of particulate and dissolved organic matter (POM and DOM), D- and L-amino acids (AA) were quantified at bloom and HNLC stations. Total hydrolyzable AA accounted for 21–25% of surface particulate organic carbon (%POCAA) at the bloom sites, but for 10% at the HNLC site. A marked decrease in %POCAA with depth was observed at the most productive stations leading to values between 3 and 5% below 300 m depth. AA contributed to only 0.9–4.4% of dissolved organic carbon (%DOCAA) at all stations. The only consistent vertical trend was observed at the most productive station (A3-2) where %DOCAA decreased from ~ 2% in the surface waters to 0.9% near 300 m. These AA yields revealed that POM and DOM were more rapidly altered or mineralized at the bloom sites compared to the HNLC site. Alteration state was also assessed by trends in C / N ratio, %D-AA and degradation index. Different molecular markers indicated that POM mostly originated from diatoms and bacteria. The estimated average proportion of POM from intact phytoplankton cells in surface waters was 45% at the bloom station A3-2, but 14% at the HNLC site. Estimates based on D-AA yields indicated that ~ 15% of POM and ~ 30% of DOM was of bacterial origin (cells and cell fragments) at all stations. Surprisingly, the DOM in HNLC waters appeared less altered than the DOM from the bloom, had slightly higher dissolved AA concentrations, and showed no sign of alteration within the water column. Unfavorable conditions for bacterial degradation in HNLC regions can explain these findings. In contrast, large inputs of labile organic molecules and iron likely stimulate the degradation of organic matter (priming effect) and the production of more recalcitrant DOM (microbial carbon pump) during iron-fertilized blooms.

scholarly journals Perspectives of the microbial carbon pump with special references to microbial respiration and ecological efficiency

2014 ◽  
Vol 11 (1) ◽  
pp. 1479-1533 ◽  
Author(s):  
H. Dang ◽  
N. Jiao
Keyword(s):  
Organic Matter ◽  
Lower Energy ◽  
Energy Production ◽  
Production Efficiency ◽  
Microbial Respiration ◽  
Ecological Efficiency ◽  
Carbon Pump ◽  
Microbial Carbon ◽  
Microbial Carbon Pump ◽  
Ecological Functioning

Abstract. Although respiration consumes fixed carbon and produce CO2, it provides energy for essential biological processes of an ecosystem, including the microbial carbon pump (MCP). In MCP-driving biotransformation of labile DOC to recalcitrant DOC (RDOC), microbial respiration provides the metabolic energy for environmental organic substrate sensing, cellular enzyme syntheses and catalytic processes such as uptake, secretion, modification, fixation and storage of carbon compounds. The MCP efficiency of a heterotrophic microorganism is thus related to its energy production efficiency and hence to its respiration efficiency. Anaerobically respiring microbes usually have lower energy production efficiency and lower energy-dependent carbon transformation efficiency, and consequently lower MCP efficiency at per cell level. This effect is masked by the phenomena that anoxic environments often store more organic matter. Here we point out that organic carbon preservation and RDOC production is different in mechanisms, and anaerobically respiring ecosystems could also have lower MCP ecological efficiency. Typical cases can be found in large river estuarine ecosystems. Due to strong terrigenous input of nutrients and organic matter, estuarine ecosystems usually experience intense heterotrophic respiration processes that rapidly consume dissolved oxygen, potentially producing hypoxic and anoxic zones in the water column. The lowered availability of dissolved oxygen and the excessive supply of nutrients such as nitrate from river input prompt enhanced anaerobic respiration processes. Thus, some nutrients may be consumed by anaerobically respiring heterotrophic microorganisms, instead of being utilized by phytoplankton for carbon fixation and primary production. In this situation, the ecological functioning of the estuarine ecosystem is altered and the ecological efficiency is lowered, as less carbon is fixed and less energy is produced. Ultimately this would have negatively impacts on the ecological functioning and efficiency of the MCP which depends on both organic carbon and energy supply.

scholarly journals An implementation strategy to quantify the marine microbial carbon pump and its sensitivity to global change

2018 ◽  
Vol 5 (4) ◽  
pp. 474-480 ◽  
Author(s):  
Carol Robinson ◽  
Douglas Wallace ◽  
Jung-Ho Hyun ◽  
Luca Polimene ◽  
Ronald Benner ◽  
...  
Keyword(s):  
Global Change ◽  
Implementation Strategy ◽  
Carbon Pump ◽  
Microbial Carbon ◽  
Microbial Carbon Pump

scholarly journals Perspectives on the microbial carbon pump with special reference to microbial respiration and ecosystem efficiency in large estuarine systems

2014 ◽  
Vol 11 (14) ◽  
pp. 3887-3898 ◽  
Author(s):  
H. Dang ◽  
N. Jiao
Keyword(s):  
Dissolved Oxygen ◽  
Carbon Fixation ◽  
Negative Impact ◽  
Energy Transduction ◽  
Metabolic Energy ◽  
Transduction Efficiency ◽  
Estuarine Ecosystems ◽  
Carbon Pump ◽  
Microbial Carbon ◽  
Microbial Carbon Pump

Abstract. Although respiration-based oxidation of reduced carbon releases CO2 into the environment, it provides an ecosystem with the metabolic energy for essential biogeochemical processes, including the newly proposed microbial carbon pump (MCP). The efficiency of MCP in heterotrophic microorganisms is related to the mechanisms of energy transduction employed and hence is related to the form of respiration utilized. Anaerobic organisms typically have lower efficiencies of energy transduction and hence lower efficiencies of energy-dependent carbon transformation. This leads to a lower MCP efficiency on a per-cell basis. Substantial input of terrigenous nutrients and organic matter into estuarine ecosystems typically results in elevated heterotrophic respiration that rapidly consumes dissolved oxygen, potentially producing hypoxic and anoxic zones in the water column. The lowered availability of dissolved oxygen and the excessive supply of nutrients such as nitrate from river discharge lead to enhanced anaerobic respiration processes such as denitrification and dissimilatory nitrate reduction to ammonium. Thus, some nutrients may be consumed through anaerobic heterotrophs, instead of being utilized by phytoplankton for autotrophic carbon fixation. In this manner, eutrophied estuarine ecosystems become largely fueled by anaerobic respiratory pathways and their efficiency is less due to lowered ecosystem productivity when compared to healthy and balanced estuarine ecosystems. This situation may have a negative impact on the ecological function and efficiency of the MCP which depends on the supply of both organic carbon and metabolic energy. This review presents our current understanding of the MCP mechanisms from the view point of ecosystem energy transduction efficiency, which has not been discussed in previous literature.

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