| Volumes and Issues Contents of Issue 3 |
www.biogeosciences-discuss.net/6/5431/2009/
doi:10.5194/bgd-6-5431-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
From heterotrophy to autotrophy: a freshwater estuarine ecosystem recovering from hypereutrophication
1University of Antwerp, Dept. of Biology, Ecosystem Management research group, Universiteitsplein 1, 2610 Anwerpen, Belgium
2Netherlands Institute of Ecology (NIOO-KNAW), Centre for Estuarine and Marine Ecology, Korringaweg 7, P.O. Box 140, 4400 AC Yerseke, The Netherlands
3GeoBiosphere Science Centre, Quaternary Sciences, Sölvegatan 12, 223 62 Lund, Sweden
4University of Potsdam, Institute of Biochemistry and Biology, Dept. of Ecology & Ecosystem Modeling, Am Neuen Palais 10, 14469 Potsdam, Germany
Abstract. Increased organic matter and nutrient loads have induced major changes in aquatic systems, including hypoxia and algal blooms. In enclosed ecosystems these changes were often not gradual due to non-linear mechanisms. Here we report a 40 year record of eutrophication and hypoxia on an estuarine ecosystem and its recovery from hypereutrophication. We observe a paradoxical increase in chlorophyll a concentrations with decreasing nutrient inputs, and 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 an autotrophic equilibrium with low ammonia inputs, and a heterotrophic equilibrium with high ammonia inputs. At intermediate ammonia inputs it displays two alternative stable states. We conclude that the recovery of hypereutrophic riverine/estuarine systems can exhibit threshold-like behaviour.
Discussion Paper (PDF, 782 KB) Interactive Discussion (Closed, 4 Comments) Final Revised Paper (BG)
Citation: Cox, T. J. S., Maris, T., Soetaert, K., Conley, D. J., Van Damme, S., Meire, P., Middelburg, J. J., Vos, M., and Struyf, E.: From heterotrophy to autotrophy: a freshwater estuarine ecosystem recovering from hypereutrophication, Biogeosciences Discuss., 6, 5431-5459, doi:10.5194/bgd-6-5431-2009, 2009. Bibtex EndNote Reference Manager XML
