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| Titel |
Organic N and P in eutrophic fjord sediments – rates of mineralization and consequences for internal nutrient loading |
| VerfasserIn |
T. Valdemarsen, C. O. Quintana, M. R. Flindt, E. Kristensen |
| 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 ; 12, no. 6 ; Nr. 12, no. 6 (2015-03-18), S.1765-1779 |
| Datensatznummer |
250117867
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| Publikation (Nr.) |
 copernicus.org/bg-12-1765-2015.pdf |
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| Zusammenfassung |
| Nutrient release from the sediments in shallow eutrophic estuaries may
counteract reductions of the external nutrient load and prevent or prolong
ecosystem recovery. The magnitude and temporal dynamics of this potential
source, termed internal nutrient loading, is poorly under\-stood. We
quantified the internal nutrient loading driven by microbial mineralization
of accumulated organic N (ON) and P (OP) in sediments from a shallow
eutrophic estuary (Odense Fjord, Denmark). Sediments were collected from
eight stations within the system and nutrient production and effluxes were
measured over a period of ~ 2 years. Dissolved inorganic nitrogen
(DIN) effluxes were high
initially but quickly faded to low and stable levels after 50–200 days, whereas
PO43− effluxes were highly variable in the different sediments.
Mineralization patterns suggested that internal N loading would quickly
(< 200 days) fade to insignificant levels, whereas internal
PO43− loading could be sustained for extended time (years). When
results from all stations were combined, internal N loading and P loading
from the fjord bottom was up to 121 × 103 kg N yr−1 (20 kg N ha−1 yr−1)
and 22 × 103 kg P yr−1 (3.6 kg P ha−1 yr−1) corresponding to 6 (N) and 36% (P) of the external
nutrient loading to the system. We conclude that the internal N loading
resulting from degradation of accumulated ON is low in shallow eutrophic
estuaries, whereas microbial mineralization of accumulated OP is a potential
source of P. Overall it appears that, in N-limited eutrophic systems,
internal nutrient resulting from mineralization of ON and OP in sediments is
of minor importance. |
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