期刊
WATER RESEARCH
卷 42, 期 4-5, 页码 977-986出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2007.09.012
关键词
sediment; phosphorus; nitrogen; silica; flux; lake; light; water column
资金
- Natural Environment Research Council [ceh010022] Funding Source: researchfish
The effects of light and temperature on nutrient cycling (silica (Si), nitrogen (N) and phosphorus (P)) between sediments and water in a shallow eutrophic lake (Loch Leven, Scotland), and consequent effects on water column nutrient stoichiometry, were assessed using a series of intact sediment core incubation experiments. Estimates of actual seasonal dark and light P-fluxes were assessed using 24-h incubations. Sediment-P uptake was observed in spring (7 degrees C) and release in autumn (12 degrees C) and summer (17,C), with the highest release rates (similar to 17MgPO(4)-Pm-2 sediment surface area d(-1)) occurring in summer. In a longer (21-day) experiment in which the effects of light (light (n = 6) and dark (n = 6)) and temperature (five 4-day cycles to represent: 7 degrees C double right arrow 13 degrees C double right arrow 23 degrees C double right arrow 13 degrees C double right arrow 7 degrees C) on water column nutrient concentrations were assessed, PO4--P, total P (TP), SiO2 and total silica (TSi) concentrations in the water column were all significantly higher under dark conditions (ANOVA, alpha = 0.05). NH4-N (ammonium N) water column concentrations were observed to be higher under dark conditions at low temperatures and higher under light conditions following a high-temperature (23 degrees C) treatment. No significant light effects were observed for water column total N (TN) concentration. Flux estimates for all nutrients measured are given. In terms of water column nutrient stoichiometry, TN:TP ratio was significantly higher under light conditions, TSi:TN was significantly lower under light conditions, and TSi:TP did not vary significantly between the dark and light treatments. The main processes acting to regulate diffusive nutrient release appeared to be photosynthetic elevation of bottom water pH and dissolved oxygen concentration (both significantly higher under light conditions) and direct microalgal sequestration. Thus, a feedback mechanism exists in recovering shallow lakes where benthic microalgae can affect the stoichiometry (to favour P/Si limitation) of the plankton, and also of the main source of nutrients back to the sediments via the disproportionate regulation of sediment P, Si and N release. (c) 2007 Elsevier Ltd. All rights reserved.
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