Sediment lipid biomarkers record increased eutrophication in Lake Fuxian (China) during the past 150 years

Organic geochemical analysis of a sediment core from Lake Fuxian was carried out to reconstruct the progression of eutrophication in this lake from ca. 1857 to 2012. The results indicate that two episodes can be identified during the eutrophication of the lake water. Both bulk geochemical proxies and sediment lipid biomarkers recorded an enhanced eutrophication in this lake since 1986. Total organic carbon (TOC), total nitrogen (TN) and phytoplankton biomarkers were most abundant in this period, indicating high phytoplankton productivity. Phytoplankton composition showed an elevated proportion of dinoflagellate and green algae relative to diatoms, in response to the anthropogenic nutrient inputs (e.g., sewage, fertilizers) since the 1980s. On the other hand, only the sediment lipid biomarker detected a minor eutrophication of the lake water between 1951 and 1986. During this period, phytoplankton biomarkers, regardless of their labile or refractory nature, exhibited a little enhanced concentration in the sediment, indicating a minor increase of phytoplankton productivity. Phytoplankton composition was characterized by a slight increase of diatoms relative to dinoflagellates and green algae. Variations of algal productivity and community structure in this period could be attributed to the nutrients (e.g., soil Si) input from catchment erosion. A causal relationship might be present between the eutrophication process of Lake Fuxian and the anthropogenic activities within the catchment. (C) 2014 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.