| 摘要: |
| 湖泊是地质历史上区域生态环境演变的重要载体，其沉积物中包含了丰富的环境演变信息。达里湖是典型的草原内陆封闭型湖泊，位于东亚夏季风的北部边缘，地理位置关键。本研究基于在达里湖采集的约238 cm沉积物岩芯 (GDL-1)，通过210Pb和137Cs (岩芯上部20 cm)、AMS14C测年，以及沉积物样品中甾醇等生物标志物含量分析，重建了近1800年以来达里湖硅藻、蓝藻等典型藻类含量的演化历史，并结合总氮(TN)、总磷(TP)、盐度(Sr/Ba)和温度(T)等环境代用指标，分析藻类群落的主要影响因素。结果显示达里湖典型藻类总量平均为2.03 ng/g(最高6.69 ng/g，最小0.53 ng/g)，其中蓝藻占比平均为60%，绿藻和硅藻占比平均为20%；环境因子对硅藻、蓝藻和典型藻类生物量的解释率分别为47.7%、55.20%和48.10%，T、TN和Sr/Ba是影响浮游植物群落的主要影响因素；硅藻占比与温度呈显著负相关，小冰期硅藻占比最高，中世纪暖期占比最低；在达里湖的高盐环境下，湖泊营养盐浓度对藻类的影响受到限制，成为藻类等生长的限制因素；Sr/Ba小于0.9时，硅藻含量与典型藻类总量随着Sr/Ba值的升高而增加，Sr/Ba大于0.9时，典型藻类总量与Sr/Ba值呈负相关关系，而硅藻则表现出对盐度具有一定的耐受性；整体上，近1800年以来，区域或全球性气候事件通过改变达里湖盐度、营养元素浓度和温度来影响典型藻类群落结构。在暖期阶段，蒸发作用增强等导致的湖泊盐度增加成为达里湖典型藻类群落结构演变的主要影响因素；在冷期，营养元素浓度和温度的降低成为湖泊水体浮游植物生物量的主要影响因素。 |
| 关键词: 生物标志物 浮游植物 群落结构 近2000年 达里湖 |
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| 基金项目:国家自然基金地区项目(52160021), 内蒙古自治区科技重大专项(2020ZD0009), 内蒙古自治区自然科学基金项目(2021MS05043), 内蒙古自治区高等学校“青年科技英才支持计划”项目(NJYT-20-A14)和内蒙古自治区科技攻关项目(2020GG0009)联合资助. |
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| Phytoplankton community evolution and driving factors in Dali Lake over the last 1800 years |
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Guo Xin, Li Wenbao, Shi Xiaohong, Liu Jinjin, Shi Yujiao
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Inner Mongolia Agricultural University IMAR Key Laboratory of Water Resources Utilization and Protection
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| Abstract: |
| Lakes are important carriers of regional ecological evolution in geological history, and their sediments contain a rich information on the environmental evolution. Dali Lake is a closed inland lake situated on the northern edge of the East Asian Summer Monsoon (EASM), making its geographic location crucial. In this paper, we successfully collected about 238 cm sediment cores (GDL-1) in Dali Lake. Using 210Pb and 137Cs (top 20 cm of the core), AMS14C and other dating methods, we analyzed the content of sterols and other biomarkers in the sediment samples, and reconstructed the evolutionary history of typical algae, such as diatoms and cyanobacteria, in Dali Lake over the past 1800 years. Then, the effects of total nitrogen (TN), total phosphorus (TP), salinity (Sr/Ba) and temperature on the algal communities were also analyzed.The results showed that the mean total algal biomass in Dali Lake is 2.03 ng/g, with cyanobacteria accounting for an average relative abundance of 60%, green algae and diatoms accounting for an average relative abundance of 20%. Environmental factors explain 47.7%, 55.20%, and 48.10% of the variation in diatom, cyanobacteria, and total algal biomass respectively. Temperature, TN, and Sr/Ba ratio are identified as major influencing factors on phytoplankton community. The relative abundance of diatoms shows a significant negative correlation with temperature, being the highest during the Little Ice Age and lowest in the Medieval Warm Period. In high-salinity conditions of Dali Lake, the influence of nutrient concentration on algae is limited, becoming a limiting factor for the growth of algae. When Sr/Ba ratio is less than 0.9, the content of diatoms and the total amount of typical algae increase with the increase of Sr/Ba value. As Sr/Ba is greater than 0.9, the total amount of typical algae is negatively correlated with Sr/Ba value, while diatoms show a certain tolerance to salinity. The biomass of the typical algal communities in Dali Lake have been affected by the combined effects of salinity, temperature and nutrient over the past 1800 years. During the warm period, the increase in lake salinity caused by enhanced evaporation became the main influence on the evolution of the typical algal community structure in Dali Lake; and the reduction in nutrient concentration and temperature became the main factors affecting the phytoplankton biomass in the lake for the cold period. |
| Key words: biomarkers phytoplankton community structure nearly 2000 years Dali Lake |
