EAPSI: Using Optical Methods to Determine the Role of Organic Nitrogen in Stimulating Harmful Algal Blooms and Contributing to Water Quality Impairment in Freshwater Lakes

全球流域城市、农业和工业的快速扩张导致淡水湖泊环境的养分（氮和磷）负荷增加，包括美国的伊利湖和奥基乔比湖以及中国的太湖。营养负荷增加的有害影响包括鱼类死亡、氧气消耗和有害藻华，这会破坏湖泊生态系统的资源（饮用水源、渔业栖息地、娱乐和旅游利用）和可持续性。从历史上看，湖泊管理策略一直侧重于控制无机氮和磷负荷。近年来，有机物作为水生系统中藻华和微生物生长的氮源的作用已得到认识。有证据表明，城市径流、农业、工业和废水处理厂排放的有机氮成分会促进藻类和细菌的生长。该项目将探讨有机氮在维持有毒蓝藻有害藻华和导致中国太湖水质受损方面的作用。该研究将与中国科学院南京地理与湖泊研究所的朱光伟博士合作进行，朱光伟博士是太湖有害蓝藻水华动态方面的著名专家。用于识别和跟踪水生系统中荧光有机物的光学技术（激发发射矩阵与并行因子分析相结合，EEM-PARAFAC）的发展使得能够快速而详细地了解淡水生态系统中有机物的动态信息。本研究将利用光学技术和有机物添加实验来扩大对有机氮在氮敏感淡水湖泊富营养化和水华动态中所起作用的理解。通过利用流域有机质来源丰富太湖的天然湖泊浮游植物和细菌组合，将探索有机氮在促进初级生产力（特别是蓝藻水华）方面的作用。结果可广泛应用于遭受有害藻华和水质损害影响的地理上多样化的营养丰富的淡水和沿海平原生态系统。该奖项属于东亚和太平洋夏季研究所项目，支持美国研究生的夏季研究，由美国国家科学基金会和中国科学技术部共同资助。

Rapid urban, agricultural, and industrial expansion in watersheds worldwide has led to increased nutrient (nitrogen and phosphorus) loading to freshwater lake environments including Lake Erie and Lake Okeechobee in the US and Lake Taihu in China. Harmful effects of increased nutrient loading include fish kills, oxygen depletion, and harmful algal blooms, which disrupt both the resources (drinking water source, fisheries habitat, recreation and tourism use) and sustainability of lake ecosystems. Historically, lake management strategies have focused on controlling inorganic nitrogen and phosphorus loading. In recent years, the role of organic matter as a nitrogen source for algal blooms and microbial growth in aquatic systems has been recognized. Evidence suggests organic nitrogen constituents from urban run-off, agriculture, industry, and wastewater treatment plant discharge promote algal and bacterial growth. This project will explore the role organic nitrogen plays in sustaining toxic cyanobacterial harmful algal blooms and contributing to water quality impairment in Lake Taihu, China. The study will be conducted in collaboration with Dr. Zhu Guangwei at the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, a noted expert on harmful cyanobacterial bloom dynamics in Lake Taihu. The development of optical techniques (excitation emission matrices coupled with parallel factor analysis, EEM-PARAFAC) to identify and track fluorescent organic matter through aquatic systems has allowed for rapid and detailed information on organic matter dynamics in freshwater ecosystems. This study will use optical techniques and organic matter addition experiments to expand the understanding of the role organic nitrogen plays in eutrophication and bloom dynamics in nitrogen-sensitive freshwater lakes. By enriching natural lake phytoplankton and bacterial assemblages from Lake Taihu with watershed organic matter sources, the role organic nitrogen plays in fueling primary productivity, specifically as cyanobacterial blooms will be explored. Results can be broadly applied to geographically-diverse nutrient-enriched freshwater and coastal plain ecosystems experiencing the effects of harmful algal blooms and water quality impairment.This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Ministry of Science and Technology of China.