העברת האות הסביבתי אל משקעי האגם: המקרה של אגם טיפר
While lake sediments offer valuable environmental records, their interpretation is often limited by our understanding of sediment-signal transfer. To address this, modern lake monitoring increasingly integrates meteorology, limnology, and sedimentation. This talk highlights two case studies from Lake Tiefer See (NE Germany) that clarify these transfer processes. First, we trace the rate, style, and magnitude of anthropogenically driven hypoxia over the last 200 years. Sedimentological analyses of multiple cores, covering the transition into hypoxic conditions, reveal that oxygen depletion began prior to the onset of varve preservation, the traditional proxy for hypoxia. Furthermore, we demonstrate that varve preservation, previously attributed to permanent water-column stratification (meromixis), actually occurs under seasonal stratification once a hypoxic threshold is crossed. Second, we examine the thermal control on endogenic calcite formation. Sediment trap data demonstrates that total calcite accumulation is proportional to the duration of summer warmth (the number of days with epilimnion temperatures > 18°C) rather than average or peak summer temperatures. This identifies endogenic calcite precipitation in Lake Tiefer See as a threshold-driven system. Ultimately, these findings are expected to improve the accuracy of paleolimnological reconstructions and enhance our ability to predict lake responses to future environmental change.
