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Investigating forced recovery from eutrophication in shallow lakes

Meis, Sebastian 2012. Investigating forced recovery from eutrophication in shallow lakes. PhD Thesis, Cardiff University.
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Release of phosphorus (P) from bed sediments to overlying waters (internal P-loading) can detrimentally alter ecological structure and function in shallow lakes. The theory of regime shifts states that shallow lakes can exist in alternative states and that shifts between states can occur as a result of disturbance. The main hypothesis of this study was that the use of a P-capping agent (Phoslock®) in shallow lakes (i.e. a controlled disturbance) will break down the internal P-loading feedback mechanism resulting in a regime shift. Experiments, ranging in scale from mesocosm to whole-lake, showed that Phoslock® significantly reduced internal P-loading by increasing the mass of P stored in more refractory sediment P-fractions relative to potentially release-sensitive P-fractions. Intact sediment core experiments highlighted that the application of high areal loads of Phoslock® can, at least temporarily, significantly alter the vertical distribution of sediment dissolved oxygen concentrations and cycling of nutrients other than P, suggesting that the application of high areal loads of Phoslock® to lakes should be avoided. Disruption of internal P-loading in Loch Flemington (Inverness, UK) caused a significant reduction of in-lake P concentrations, a decrease of phytoplankton biomass and an increase in water clarity. The observed changes were generally comparable to those observed in long-term multi-lake studies investigating the recovery of shallow lakes following external P-load control, but occurred over a shorter time scale (1 year compared to decades). Alterations in ecological structure and function indicated that a change in state from a ‘phytoplankton dominated turbid state’ to a ‘macrophyte dominated clear water state’ was achieved in Loch Flemington. This study confirms that it is possible to force a state change in shallow lakes by disturbing feedback mechanisms and documents further work required to improve the efficacy of the Pcapping approach in lake remediation.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Earth and Ocean Sciences
Subjects: Q Science > QD Chemistry
Q Science > QE Geology
Funders: DAAD Scholarship
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:16

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