Is Phosphorus Retention in Autochthonous Lake Sediments Controlled by Oxygen or Phosphorus?

• Published in: Limnology and oceanography Vol. 51; no. 1; pp. 763 - 771
• Main Authors: Moosmann, Lorenz, Gaechter, Rene, Mueller, Beat, Wueest, Alfred
• Format: Journal Article
• Language: English
• Published: Waco, TX The American Society of Limnology and Oceanography 01-01-2006; American Society of Limnology and Oceanography
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; Geochemistry; Hydrology; Hydrology. Hydrogeology; Kettle holes; Lake sediment cores; Lakes; Limnology; Mineralogy; Oxygen; Phosphorus; Phosphorus cycle; Sediment core samples; Sediments; Silicates; Synecology; Tissue oxygenation; Water geochemistry; Central Europe; Switzerland; Switzerland, Swiss Plateau; fresh-water environment; eutrophication; Europe; water balance; concentration; inventory; nutrients; drill cores; lake sediments; modern; burial; hydrochemistry; lacustrine sedimentation; ecosystems; lakes; export; oxygen; retention; phosphorus
• ISSN: 0024-3590; 1939-5590
• DOI: 10.4319/lo.2006.51.1_part_2.0763

Eutrophication of various lakes on the Swiss Plateau was targeted in the 1980s by reducing external nutrient loading and installing aeration/oxygenation systems. For five eutrophic lakes, three of which have been artificially oxygenated and aerated for almost 20 yr, phosphorus (P) balances were established using input, water-column inventory, export via the outlet, and sediment core data. To separate the effects of aeration/oxygenation from the effects of P-input reduction, two measures of P retention were determined-the ratio of net sedimentation to input and the ratio of net sedimentation to gross sedimentation. A comparison among the five lakes shows that, presently, P retention does not differ significantly between lakes with aeration/oxygenation and lakes with an anoxic hypolimnion, whereas retention at times of maximum P concentrations in the 1970s and 1980s was significantly lower compared with retention in today's moderately eutrophic lakes. This is in agreement with the finding that net sedimentation in all lakes remained relatively constant between 280 and$950 kg km^{-2}$, independent of their P concentration. It is shown that constant net sedimentation is likely to prevail as long as P concentrations remain above a critical value of around$40 mg m^{-3}$. Constant net sedimentation indicates that permanent deposition of P is limited by the sediment's binding capacity. Oxic conditions in the hypolimnion do not necessarily increase this capacity because redox-dependent P species may still be released within the anoxic bulk sediment and diffuse back into the water column. To characterize the P retention capacity of anoxic sediments, we suggest that the P burial rate be determined from dated sediment cores rather than from input/output balances.