Drivers of change and ecosystem status in a temperate lake over the last Post-Glacial period from 14.5 kyr

Understanding the long-term dynamics of ecological communities on the centuries-to-millennia scale is important for explaining present-day biodiversity patterns. Placing these patterns in a historical context could yield reliable tools for predicting possible future scenarios. Paleoarchives of macro+ and micro-fossil remains, and most importantly biomarkers such as fossil pigments and ancient DNA present in various sedimentary deposits, allow long term changes in ecological communities to be analysed. We use recent compilations of data including fossil pigments, metabarcoding of sedimentary ancient DNA and microfossils together with data analysis to understand the impact of gradual versus abrupt climate changes on a lake`s ecosystem status over the last 14.5 kyr. We give examples of hypotheses that need long-term data, which can be addressed using well-established paleoproxy variables. These variables describe the climate, together with vegetation change and the appearance of anthropogenic forcing, either as a gradual change or an abrupt event. We were able to detect abrupt changes in the lake ecosystem during the stable period of the Holocene Thermal Maximum and we highlight the increased frequency and degree of perturbation in lakes due to non-immediate human activity over a larger region. Both observations demonstrate an impaired relationship between a gradual external driver and ecosystem response and apply to future scenarios of climate warming and increased human impact in north-eastern Europe.