Multiple Nitrogen Utilization Strategies and Phytoplankton Species diversity: Nitrate Assimilation in N2-fixing Bloom-Forming cyanobacteria

过量的氮（N）负荷支持许多水生生态系统中的富营养化。 本研究将评估富营养化过程中涉及的藻类群体--固氮蓝藻的营养生理和生态作用。 这些蓝细菌通过固定大气中的二氮（N2）来支持它们对氮的需求;然而，一些物种也可以利用硝酸盐，一种溶解形式的结合氮。 入侵固氮蓝藻是否成功地与本地物种竞争，在系统中经历增加硝酸盐负荷可能取决于物种特异性的生态平衡之间的硝酸盐和N2利用。 为了验证这一假设，氮的吸收和利用机制的作用可能促进优势的入侵和有毒的raciborskii在本地鱼腥藻。在佛罗里达湖，将被调查。 本研究将采用现场操作和基于培养的研究，以完善浮游植物群落调控和管理所依据的生态学理论。 由于其营养生理的复杂性，固氮蓝藻在管理水质时存在问题。 这项研究将提供有价值的信息管理人员制定营养减少战略，以控制系统的富营养化与滋扰（如有毒）蓝藻。 此外，在用于饮用和娱乐的沃茨中有毒的蓝藻水华是不希望的。有毒蓝藻的影响最终会影响到食物链，包括人类。 研究生将在研究中发挥不可或缺的作用，卡罗莱纳环境项目的本科生将在课程中利用该项目，并通过独立学习参与研究。

Excessive nitrogen (N) loading supports eutrophication in many aquatic ecosystems. This study will assess the nutritional physiology and ecological role of nitrogen-fixing cyanobacteria, an algal group implicated in the eutrophication process. These cyanobacteria support their N needs by fixing atmospheric di-nitrogen (N2); however some species can also utilize nitrate, a dissolved form of combined nitrogen. Whether invasive N-fixing cyanobacteria successfully compete with native species in systems experiencing increased nitrate loading may depend on species-specific ecological trade-offs between nitrate and N2 utilization. To test this hypothesis, the roles of N uptake and utilization mechanisms potentially promoting dominance of the invasive and toxic Cylindrospermopsis raciborskii over native Anabaena spp. in Florida lakes, will be investigated. In-situ field manipulations and culture-based studies will be used.This study will improve the ecological theory on which the regulation and management of phytoplankton communities is based. Because of the complexity of their nutritional physiology, N2-fixing cyanobacteria are problematic when managing water quality. This study will provide valuable information to managers developing nutrient reduction strategies to control eutrophication in systems with nuisance (e.g. toxic) cyanobacteria. Additionally, toxic cyanobacterial blooms are undesirable in waters used for drinking and recreation. The impacts of toxic cyanobacteria can ultimately be felt up the food chain, including humans. Graduate students will play an integral role in the research, and undergraduates in the Carolina Environmental Program will utilize the project in coursework and participate in the research through independent study.