CLIMATE-CHANGE AS THE PRIMARY CAUSE FOR PH SHIFTS IN A HIGH ALPINE LAKE

Chemical and biological sedimentary records of a high alpine lake were used to reconstruct palaeoecological conditions and compared with two centuries of instrumental temperature measurements. Air temperature d etermined the lake water pH throughout the past 200 yr almost regardle ss of the level of atmospheric deposition. Our data suggest a strong c limate forcing of the acid-base balance in sensitive high-altitude lak es. Their physico-chemical conditions and biota strongly depend on the duration of ice and snow cover which is significantly different betwe en warm and cold periods. Beside changes in weathering rates, in-lake alkalinity generation and water-retention time, delayed freezing in au tumn and earlier ice-out dates with a shorter duration of CO2 over-sat uration could be crucial for the tight temperature-pH coupling.