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| Titel |
Perspectives on the microbial carbon pump with special reference to microbial respiration and ecosystem efficiency in large estuarine systems |
| VerfasserIn |
H. Dang, N. Jiao |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 14 ; Nr. 11, no. 14 (2014-07-24), S.3887-3898 |
| Datensatznummer |
250117524
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| Publikation (Nr.) |
 copernicus.org/bg-11-3887-2014.pdf |
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| Zusammenfassung |
| 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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