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的富营养化。本研究将评估固氮蓝藻的营养生理和生态作用，这是一种涉及富营养化过程的藻类群。这些蓝藻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，一种溶解形式的组合氮。在硝酸盐负荷增加的系统中，入侵的固氮蓝藻是否能成功地与本地物种竞争，可能取决于硝酸盐和N2利用之间的物种特异性生态权衡。为了验证这一假设，我们将研究在佛罗里达湖泊中，氮的吸收和利用机制可能促进入侵和有毒的raciborski圆柱形精子对原生水藻的优势。将使用现场操作和基于培养的研究。本研究将进一步完善浮游植物群落调控管理的生态学理论基础。由于其营养生理的复杂性，固氮蓝藻在管理水质时是有问题的。本研究将提供有价值的信息，管理人员制定营养减少战略，以控制富营养化系统与滋扰（如有毒）蓝藻。此外，有毒的蓝藻在饮用水和娱乐用水中是不受欢迎的。有毒蓝藻的影响最终可以在食物链中感受到，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作业中利用该项目，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.