Limnological responses to environmental changes during the last 3,000 years revealed from a varved sequence of Lake Lubi?nskie (western Poland)

Sediments from Lake Lubi ' nskie, western Poland, were investigated to determine the limnological responses to environmental changes during the last 3,000 years. To identify the mechanisms driving the eutrophication in the lake, we distinguished six lithozones along with five major varve microfacies. An age-depth model based on varve counting and radiometric measurements was established resulting in final age of 946 +113/-144 before the Common Era at the bottom of the composite profile. Varve microfacies as well as geochemical, pollen, and diatom data was used to determine major phases of landscape and lake ecosystem transformations. Our data shows that until the 4th century of the Common Era, conditions in the lake were stable. Several shifts occurred before the first millennium, when changes were observed in every proxy as a response to the increased agri-cultural activity in the area as well as climate fluctuations. The highest frequency of shifts was observed from the 17th century onward and mirrored further deforestation (decrease in arboreal pollen), accelerated erosion (in-crease in Ti), increased nutrient delivery (increased total nitrogen content), and better ventilation of the water body (higher Mn/Fe ratio). Simultaneously, the lake became more eutrophic as a response to changes in the lake catchment area. Our study suggests that inferred lake-level changes are primarily related to human activity in the catchment area.

Automated summary

Sediments from Lake Lubi'nskie in western Poland were analyzed to investigate the effects of environmental changes on the lake's limnology over the past 3,000 years. By studying varve microfacies, geochemical, pollen, and diatom data, as well as using an age-depth model based on varve counting and radiometric measurements, major phases of landscape and lake ecosystem transformations were identified. The study suggests that human activities in the catchment area, such as agriculture and deforestation, have had a significant impact on the lake's eutrophication and inferred lake-level changes.