人类活动影响下异龙湖浮游植物碳氮稳定同位素变化特征  

Pattern in changes of carbon and nitrogen stable isotopes of phytoplankton in Yilong Lake under the influence of human activities

作　　者：王旭 郭雯 王明果 李平[1] 温雯雯[1] 陈丽[1] 郑昕 黄林培[1] 陈光杰[1] WANG Xu;GUO Wen;WANG Ming-guo;LI Ping;WEN Wen-wen;CHEN Li;ZHENG Xin;HUANG Lin-pei;CHEN Guang-jie(Yunnan Key Laboratory of Plateau Geographic Processes and Environmental Change,Faculty of Geography,Yunnan Normal University,Kunming 650500,China;Meteorological Bureau of Fengning Manchu Autonomous County,Chengde 068350,China;Yunnan Geological Mine Mapping Academy Co.,Ltd,Kunming 650217,China)

机构地区：[1]云南师范大学地理学部,云南省高原地理过程与环境变化重点实验室,云南昆明650500 [2]河北省丰宁满族自治县气象局,河北承德068350 [3]云南省地矿测绘院有限公司,云南昆明650217

出　　处：《中国环境科学》2023年第6期3087-3099,共13页China Environmental Science

基　　金：国家自然科学基金(42067064,42171072);云南省院士专家工作站(202005AF150005,2017IC063);云南省重点研发计划(202203AC100002-02);异龙湖高原浅水湖泊云南省野外科学观测研究站(202305AM070002)联合资助。

摘　　要：于2020年9月~2022年6月在异龙湖开展了20个点位、8个季节的水体水质、浮游植物碳氮同位素信号等内容的系统调查与对比分析.结果表明,浮游植物δ^(13)C信号分布范围为-28.98‰~-22.32‰,呈现了丰水年份(-26.89‰±1.34‰)低于枯水年份(-25.30‰±0.97‰)、9月高于其他月份等变化模式,同时出现了西部湖区高于中部、东部湖区的空间分布特征.浮游植物δ^(15)N信号分布范围为-0.28‰~10.25‰,且丰水年份(6.28‰±1.07‰)高于枯水年份(2.78‰±1.55‰),施肥季节(6、12月)低于其他季节,以及在雨季(9月)和旱季初期(12月)西部湖区高于中部、东部湖区的空间分布特征.统计分析表明,随着异龙湖水量的上升,具有较低δ^(13)C信号的流域无机碳输入增加、水体富营养化程度降低,可能改变了浮游植物利用的无机碳源及其生长速率,从而造成了浮游植物δ^(13)C信号的显著下降,反映了调水补水措施等人类活动影响下浮游植物δ^(13)C信号的快速响应.同时,浮游植物较低的δ^(15)N分布特征及其与水体NH4+-N浓度密切相关,反映了异龙湖氮素来源于以氨肥为主的农业面源污染影响,并通过浮游植物吸收等过程影响了湖泊生态系统的氮循环模式.而有机肥替代化肥措施实施后异龙湖浮游植物δ^(15)N呈现出随水量显著升高的特征,反映了生态环境修复措施显著改变了异龙湖的氮素来源.MixSIAR模型结果表明,异龙湖氮源中农业面源污染从枯水年份的88.4%下降至丰水年份的79.0%,其中化肥贡献率从41.2%下降至14.0%,有机肥占比从47.2%上升到65.0%,而点源污染贡献率则从11.6%升高至21.0%.由此可见,调水补水工程、有机肥替代化肥等人类治理活动降低了异龙湖水体的营养盐浓度,并通过增加δ^(13)C偏低的流域碳源和δ^(15)N偏高的有机肥氮源导致浮游植物δ^(13)C信号的降低和δ^(15)N信号的升高,反映了湖泊治理和环境修复措施�From September 2020 to June 2022,a spatial investigation and seasonal analysis of water quality and carbon and nitrogen isotope signals of phytoplankton were carried out across 20 sites of Yilong Lake over 8seasons.The results showed that the distribution ofδ^(13)C signal of phytoplankton ranged from-28.98‰to-22.32‰,showing lower values in wet year(-26.89‰±1.34‰)than in dry year(-25.30‰±0.97‰),and higher values in September than in other months.Meanwhile,the spatial distribution ofδ^(13)C signal showed higher values in western lake basin than those in central and eastern lake basins.Theδ^(15)N signal of phytoplankton varied from-0.28‰to 10.25‰,and was significantly higher in wet year(6.28‰±1.07‰)than in dry year(2.78‰±1.55‰).Meanwhile,the values of phytoplanktonδ^(15)N were lower in fertilization season(June and December)compared to other seasons,and also higher in rainy season(September)and early dry season(December)than those in central and eastern lake basins.With increasing water volume in Yilong Lake,there was an increase in inorganic carbon input and a decrease in nutrient levels,resulting in a significant decline in phytoplanktonδ^(13)C signal.This may reflect the rapid response of phytoplanktonδ^(13)C signal linked to human activities such as water diversion and replenishment measures.Meanwhile,the lowerδ^(15)N values of phytoplankton are closely related to lake-water NH4+-N concentration,reflecting the role of nitrogen pollution from agricultural non-point sources(mainly ammonia fertilizer)in affecting phytoplankton absorption.However,theδ^(15)N value of phytoplankton increased significantly with expanding water volume along with a replacement of chemical fertilizers by organic fertilizers during agricultural fertilization,a measure taken for mitigating lake eutrophication.The results of MixSIAR model showed that nutrient loading derived from agricultural non-point sources decreased from 88.4%in the dry year to 79.0%in the wet year,with the contribution of point source

关 键 词：异龙湖 浮游植物 碳氮稳定同位素 湖泊修复 同位素混合模型 

分 类 号：X524[环境科学与工程—环境工程]