This study examines changes in lake-water total organic carbon (LW-TOC) and lake sediment geochemistry in two lakes, Stångtjärnen and Holtjärnen in (Dalarna, Sweden), during the Holocene and the role of the historic forest grazing and farming (fäbod-system). The aims of the study were to: 1. Discern the effects of natural processes on the lake’s biogeochemistry in different position in the landscape. 2. Identify the effects and differences in intensity of historic land-use on the lakes. A multi-proxy study was conducted encompassing multi-element (15) geochemistry, biogenic silica, LW-TOC, chlorophyll a and published pollen records. The first lake, Stångtjärnen, is shaped and influenced by surrounding mires, which developed shortly after deglaciation and stabilized the LW-TOC at 19 mg L-1 throughout most of the Holocene, while Holtjärnen, a small upland lake, changed from a productive lake (BSi: 35 %), low humic (LW-TOC: 8 mg L-1) to a less productive (BSi: 4 %) more humic lake (LW-TOC: 12 mg L-1) in 7300 BP. The intensification of agricultural land-use (e.g. hay-making) in Stångtjärnen reduced the concentrations of organic associated elements (Br, Cl) and LW-TOC and increased lithogenic elements (K, Ti), while Holtjärnen showed less anthropogenic influence. The comparison between the two lakes displayed the intensive influence of land-use on the Stångtjärnen catchment, showcased by changes in the sediment geochemistry, vegetation composition and the extent of the forest-grazing system in a landscape perspective. In response to the changes of the Holocene, Stångtjärnen’s mires became the main influence, while Holtjärnen was more sensitive to changes.

Long-term dynamics of lake-water total organic carbon (LW-TOC) concentrations in freshwater lakes provide an important perspective on the recent increases in LW-TOC observed in many of these systems and may assist with the identification of natural and anthropogenic drivers of change. This study examines how LW-TOC in Dragsjön, a lake situated in an area with a long history of anthropogenic land use, has changed in response to natural and anthropogenic perturbations throughout the Holocene. To provide a better understanding of the processes involved, a multi-proxy study was conducted and included multi-element geochemistry (17 major and trace elements), biogenic silica, organic matter (OM) content and composition, and the faecal biomarker “coprostanol”. The direct biomarker for anthropogenic presence, “coprostanol”, and a detailed characterisation of OM composition are for the first time applied for tracing changes in LW-TOC. Natural processes contributed to stable LW-TOC concentrations in Dragsjön for most part of the Holocene. Humans were present in the catchment from AD 100 as indicated by coprostanol, but did not begin to affect LW-TOC until c. AD 1500. In the last 500 years LW-TOC steadily declined from 17 to 10 mg L-1 in response to anthropogenic alterations to the terrestrial biomass balance. The increase in LW-TOC during the last 70 years likely represents a recovery from anthropogenic disturbance rather than a baseline shift in response to any of the number of proposed recent stressors. The faecal biomarker coprostanol and OM composition provided information essential for identifying and characterising the effects of anthropogenic disturbance.