A sediment record of environmental change in and around Lake Lugu, SW China, during the past two centuries

Sediment lipid biomarkers and major elements record three periods of environmental conditions in and around Lake Lugu during the past ~190 years. The first period, ca. 1820–1946, represents a time when there was minimal anthropogenic impact in the watershed. The period from 1946 to 1987 was characterized by major land-use change in the catchment, including removal of the native forest. In response, allogenic clastic mineral inputs to the lake exhibited a minor increase, whereas terrestrial plant inputs decreased to their lowest level. Aquatic algal productivity (diatoms and dinoflagellates) and the proportion of diatoms to dinoflagellates displayed a decreasing trend, indicating progressive nutrient depletion. The last stage, from 1987 to 2012, was caused mainly by development of tourism near Lake Lugu. Rock and soil erosion around the lake reached maximum values during this period, in part a consequence of earlier logging, which resulted in a rapid increase of clastic mineral input to the lake. Terrestrial plant input to the lake showed a minor increase in response to ecological restoration and reforestation activities. The lake is now at risk of becoming more nutrient-rich as a consequence of increasing sewage discharge from tourism, and the highest algal productivities and diatom proportions were recorded in this period. Nevertheless, Lake Lugu remains relatively unproductive.