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| Titel |
Coupling of primary production and diel nitrate dynamics in a eutrophic lowland river system in central Germany |
| VerfasserIn |
Michael Rode, Susanne Halbebel, Muhammad Rehan Anis, Markus Weitere |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094581
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| Publikation (Nr.) |
 EGU/EGU2014-9999.pdf |
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| Zusammenfassung |
| River ecosystem nutrient cycling and export are closely tied to the metabolic activity of
primary producers. Although general patterns of diel variation in nutrient concentrations are
known, recently developed in situ nutrient sensors allow description of fine-scale
patterns of variation for extended durations, and they can potentially be used to
quantify autotrophic assimilation. We used high frequency in situ measurements of
nitrate (NO3) and dissolved oxygen (DO) in the Bode River system of the TERENO
hydrological Observatory of the Helmholtz-Association in central Germany to i) evaluate
seasonal variation and river scale dependency of GPP and to ii) generate independent
estimates of assimilatory nitrogen demand. We analyzed two year continues data
(15 min interval) from four measurement stations ranging from the Selke third
order forested stream in the lower mountain range to the sixth order lowland Bode
River.
We are able to show that GPP follows a clear seasonal variation with highest values of up
to 3 gO2m-2d-1 in spring and an additional second peak during litter fall in autumn in the
small forested stream. The lowland river shows a similar but less pronounced pattern with
distinct higher GPP values of up to 6 gO2m-2d-1. Surprisingly this two modal behavior was
not found for the mid sized fourth order arable Selke stream with higher light availability.
GPP strongly corresponded to the day length in the growing season showing the highest GPP
of up to 8 gO2 m-2d-1 in summer. This may be caused by high periphyton growth due to
low dense riparian vegetation. A clear relationship of GPP and diel amplitudes of nitrate
concentration could be observed in all streams and rivers but these relationships
could only be identified for periods with highest GPP of each individual streams. In
addition corresponding correlations (r) ranged between 0.5 and 0.6. The results show
that high frequency in situ measurements potentially allow quantifying GPP and
assimilatory nutrient uptake and may help to better calculate nutrient retention in rivers. |
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