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| Titel |
A macro-tidal freshwater ecosystem recovering from hypereutrophication: the Schelde case study |
| VerfasserIn |
T. J. S. Cox, T. Maris, K. Soetaert, D. J. Conley, S. Damme, P. Meire, J. J. Middelburg, M. Vos, E. Struyf |
| 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 ; 6, no. 12 ; Nr. 6, no. 12 (2009-12-10), S.2935-2948 |
| Datensatznummer |
250004222
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| Publikation (Nr.) |
 copernicus.org/bg-6-2935-2009.pdf |
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| Zusammenfassung |
| We report a 40 year record of eutrophication and hypoxia on an estuarine
ecosystem and its recovery from hypereutrophication. After decades of high
inorganic nutrient concentrations and recurring anoxia and hypoxia, we
observe a paradoxical increase in chlorophyll-a concentrations with
decreasing nutrient inputs. We hypothesise that algal growth was inhibited
due to hypereutrophication, either by elevated ammonium concentrations,
severe hypoxia or the production of harmful substances in such a reduced
environment. We study the dynamics of a simple but realistic mathematical
model, incorporating the assumption of algal growth inhibition. It shows a
high algal biomass, net oxygen production equilibrium with low ammonia
inputs, and a low algal biomass, net oxygen consumption equilibrium with high
ammonia inputs. At intermediate ammonia inputs it displays two alternative
stable states. Although not intentional, the numerical output of this model
corresponds to observations, giving extra support for assumption of algal
growth inhibition. Due to potential algal growth inhibition, the recovery of
hypereutrophied systems towards a classical eutrophied state, will need
reduction of waste loads below certain thresholds and will be accompanied by
large fluctuations in oxygen concentrations. We conclude that also
flow-through systems, heavily influenced by external forcings which partly
mask internal system dynamics, can display multiple stable states. |
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