We measured lipid biomarkers (n-alkanes [n-ALKs] and n-alkanoic acids [n-FAs]) and other components of organic matter (total organic carbon [TOC] and total nitrogen [TN]) in a sediment core from Lake Issyk-Kul, Central Asia, to infer environmental changes in and around the lake during the last ∼300 years. Stratigraphic shifts in lipid biomarkers, TOC and TN, indicate three distinct environmental stages in the lake over the past three centuries: (1) Stage I (1670s–1790s, 51–36 cm sediment depth) corresponds to a period of stable hydrology in the lake, reflected by relatively constant concentrations of n-ALKs and n-FAs and values of related indexes. The interval was a period of relatively low trophic state. Natural factors were the main controls on environmental changes in and around the lake. (2) Stage II (1800s–1970s, 35–15 cm sediment depth) was a period when human activities began to exert influence on the environment in and around the lake. Enhanced agricultural exploitation and greater regional rainfall resulted in delivery to the lake of more land-derived lipids. Logging activity around the lake altered the vegetation, as revealed by shifts in C₂₇/C₃₃ ratios and the average chain length (ACL₂₇₋₃₃). A significant decline in lake level caused by excessive water consumption impacted aquatic macrophytes, as revealed by a reduction in macrophyte indicators. Lower nutrient concentrations were inferred for this period. (3) Stage III (1980s–present, 14–0 cm sediment depth) corresponds to a period of accelerating eutrophication. Before year 2000, lake level declined steadily as a result of low rainfall (drought) and high evaporation, which exerted a strong influence on the lake condition. In addition, anthropogenic activities contributed to lake eutrophication. After 2000, the lake experienced a dramatic increase in trophic state, characterized by high algal productivity, as indicated by greater TN, short-chain n-ALKs and short-chain n-FAs. The change was probably caused by flourishing tourism around the lake. In summary, environmental changes in and around Lake Issyk-Kul during the past ∼300 years were originally driven largely by natural factors such as shifts in regional precipitation amount. Human activities (e.g. logging, agriculture, water extraction, and more recently, tourism) took on increasingly important roles during the last two centuries, affecting watershed vegetation, the lake primary producer community and lake trophic status. Changes recorded in the lake sediments over the last ∼300 years are in good agreement with historical records.

我们测量了来自湖的沉积物核心中的脂质生物标志物（n-烷烃 [ n- ALK] 和n-烷酸 [ n- FAs]）和其他有机物成分（总有机碳 [TOC] 和总氮 [TN]）伊塞克湖，中亚，以推断过去 300 年中湖泊内部和周围的环境变化。脂质生物标志物 TOC 和 TN 的地层变化表明过去三个世纪湖泊中的三个不同环境阶段：(1) 阶段 I（1670 年代至 1790 年代，51 至 36 厘米沉积物深度）对应于该湖中的一个稳定水文时期。湖，反映为相对恒定的n- ALK 和n-FAs 和相关指标的值。这段时间是营养状态相对较低的时期。自然因素是湖内外环境变化的主要控制因素。(2) 第二阶段（1800-1970 年代，35-15 cm 沉积深度）是人类活动开始对湖内和湖周围环境产生影响的时期。增强的农业开发和更大的区域降雨导致更多的陆源脂质输送到湖中。湖周围的伐木活动改变了植被，这通过 C ₂₇ /C ₃₃比率和平均链长 (ACL _27-33）。正如大型植物指标的减少所揭示的那样，过度用水导致湖泊水位显着下降影响了水生大型植物。推断该时期的营养物浓度较低。(3) 第三阶段（1980 年代至今，14-0 厘米沉积物深度）对应于加速富营养化的时期。2000年以前，由于降雨量少（干旱）和蒸发量大，湖泊水位稳步下降，对湖泊状况影响较大。此外，人为活动导致湖泊富营养化。2000 年后，该湖经历了营养状态的急剧增加，以高藻类生产力为特征，如 TN、短链n- ALK 和短链n-FA。这种变化可能是由于湖周围的旅游业蓬勃发展造成的。综上所述，过去 300 年来伊塞克湖及其周边环境的变化主要是由区域降水量变化等自然因素驱动的。在过去的两个世纪里，人类活动（例如伐木、农业、取水以及最近的旅游业）发挥了越来越重要的作用，影响了流域植被、湖泊初级生产者群落和湖泊营养状况。近 300 年来记录的湖泊沉积物变化与历史记录非常吻合。