近70年滇池有机质来源和生产力变化的沉积记录

The sedimentary record of organic matter source and productivity variation in Dianchi Lake during the past 70 years

总有机碳(TOC)、稳定碳同位素(δ^(13)C)、岩石热解分析(Rock-Eval)和甾醇生物标志物等有机地球化学指标用于研究滇池过去70年沉积物有机质的来源及水体生产力的变化。C/N、δ^(13)C、氢指数(HI)表明滇池沉积物有机质主要为水生来源,且主要为藻类有机质。初级生产力指标(热解烃峰参数(S2)、HI、δ^(13)C)和浮游植物甾醇(菜籽甾醇、甲藻甾醇)含量从2000年以后快速增加,而从近几年开始增速放缓或开始下降,说明滇池水体生产力在过去几十年不断上升,不过在最近得到一定控制,这与滇池沉积物营养盐的变化趋势相似。对生产力指标和浮游植物甾醇与环境因子如5年移动平均气温(T_(5))、总氮(TN)、总磷(TP)进行相关分析,结果表明滇池生产力变化与环境因子呈现显著的正相关关系,说明气候变暖和营养盐增加均促进该水域藻类的繁殖;此外,多元线性回归分析结果表明,TN是影响滇池生产力变化的主要环境因子。研究结果对探寻水体富营养化过程及影响因子,并对湖泊管理和水华防治工作提供科学依据。

Dianchi Lake is a eutrophic lake located in Yunnan-Guizhou Plateau.Sediment organic matter preserves a large amount of information,which can be used to trace the source of organic matter and changes in productivity.Total organic carbon(TOC),stable carbon isotope(δ^(13)C),Rock-Eval analysis,sterol biomarkers,and other organic geochemical proxies were used to investigate the sedimentary organic matter source and aquatic productivity change in Dianchi Lake over the past 70 years.One sediment core(24°47'N,102°41'E,water depth 4.37 m,core length 34cm)was collected in the lake for this study.C/N,δ^(13)C,and hydrogen index(HI)indicated that the sedimentary organic matter in Dianchi Lake was mainly originated from autochthonous sources,and primarily originated from aquatic phytoplankton.Productivity indicators(S2,HI,andδ^(13)C)and phytoplankton sterols(brassicasterol and dinosterol)were rapidly elevated since 2000 AD,but were slowly elevated or started to decline in recent years.The above observation demonstrated that the aquatic productivity in Dianchi Lake was elevated in the past 70 years,but was slowly enhanced recently.This trend was similar to the trend of total nitrogen(TN)and total phosphorus(TP)in Dianchi Lake sediments.The statistics analysis of productivity indicators and phytoplankton sterols with environmental factors,such as five-year moving average air temperature(T_(5)),TN,TP demonstrated significant correlation,indicating that climate warming and increasing nutrients promoted the growth of algae in Dianchi Lake.In addition,the multiple linear regression analysis suggested that TN was the main factor affecting the change of productivity in Dianchi Lake.These results can provide scientific basis for exploring the process and influencing factors of eutrophication,and for lake management and algal bloom prevention.