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Precipitation and Dissolution of Calcite in a Swiss High Alpine Lake
Christian Ohlendorf and Michael Sturm
Arctic, Antarctic, and Alpine Research
Vol. 33, No. 4, Symposium: High-Mountain Lakes and Streams: Indicators of a Changing World (Nov., 2001), pp. 410-417
Published by: INSTAAR, University of Colorado
Stable URL: http://www.jstor.org/stable/1552550
Page Count: 8
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Water chemistry and sediment trap data from the 18.9-m-deep, high-altitude, hard-water lake Hagelseewli (2339 m asl.) indicates that biogenic induced calcite precipitation occurs in a water depth of 6 to 9 m at a temperature of 4°C. Our data indicates that calcite precipitation takes place as a short pulse that lasts less than 14 d in response to photosynthetic CO2 uptake in late summer probably by cyanobacterial picoplankton. In up to 8.4 times supersaturated water 30 μm large calcite crystals precipitate that show surface features typical for eutrophic lakes (rough surface and enhanced columnar growth). Subsequently, during the long period of ice coverage calcite is completely dissolved in strongly undersaturated bottom waters. Sediment calcite concentrations therefore are below 0.3%, although the comparison of trap fluxes and sediment accumulation rates indicates that they could be as high as 25%. The theoretical annual accumulation of calcite in Hagelseewli is similar in magnitude to a single spring precipitation event in a low-altitude temperate, hardwater lake. In the most recent sediments the occurrence of higher amounts of organic carbon and sulfur indicates increasing bottom water anoxia during the last 30 to 40 yr.
Arctic, Antarctic, and Alpine Research © 2001 Regents of the University of Colorado, a body corporate, contracting on behalf of the University of Colorado at Boulder for the benefit of INSTAAR