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

Hounshell Alexandria G, Morehead City NC

Investigators

Abstract

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.