Publication Date:
2015-10-20
Description:
Biogenic calcite precipitation is the removal of calcite (CaCO 3 ) from the epilimnion to the sediments of hard-water lakes during summer stratification, caused by increased pH during algal blooms and by nucleation of calcite crystals on surfaces of micro-algae. Although this phenomenon has been studied for decades, details of the underlying mechanisms are still debated. Using results of approximately 70,000 alkalinity measurements from 13 hard-water Swiss lakes (each with approximately 30 yr to 50 yr of monitoring), we demonstrate that (i) calcium carbonate-buffered lakes act as alkalinity sinks during summer stratification but act as CO 2 sources during and immediately after spring overturn; (ii) as the alkalinity concentration ([Alk mix ]) and the total phosphorus concentration ([TP mix ]) at spring overturn increase, increasingly more alkalinity is lost from the epilimnion during summer stratification; (iii) [Alk mix ] is determined by the lake's discharge-weighted average inflow concentration ([Alk in ]), flushing rate, mean depth and [TP mix ]; and (iv) [Alk in ] depends on the mineralogy and the land use affecting in-soil nitrification of ammonia and subsequent calcite dissolution in the catchment.
Print ISSN:
0024-3590
Electronic ISSN:
1939-5590
Topics:
Biology
,
Geosciences
,
Physics
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