The Nutritional Physiology of Phytoplankton Mixotrophs: Eecological and Evolutionary Ramifications

拟议项目的目标是确定关键的生理和生态过程，这些过程使藻华物种能够胜过其他共生的浮游植物和细菌。世界各地沿海水域浮游植物群落结构的变化以及藻华发生频率和持续时间的增加已被归因于养殖富营养化。例如，在过去的50年里，切萨皮克湾系统经历了物种多样性的减少和水华生产者生物量的增加。溶解有机物（DOM）可能促进有害藻类的生长，引发藻华。藻华物种可以吸收和利用溶解有机氮（DON）和溶解有机磷（DOP），从而促进富营养化。由于DON和DOP也含有碳(C)，吸收也可以为自养光合作用提供大量的异养补贴。生物在自养和异养代谢之间“交换”的能力可能提供了明显的进化优势，因为沿海地区越来越多地受到人为活动引起的营养富集的影响。了解藻华和群落结构变化的生态影响的一个主要限制是缺乏对鞭毛藻和其他形成藻华的生物的基本生理知识。本研究将有助于了解混合营养盐在环境中形成单特异性水华的生理因素。这项研究将集中在靠近詹姆斯河口的切萨皮克湾下游进行实地实验。浮游植物（相对于细菌）对有机化合物的吸收将在水华期间的自然群落中进行评估。放射自显影和抗生素治疗将用于控制物种多样性和藻类生物量。将进行营养富集生物测定，以确定自然组合中营养模式的竞争结果和转变（例如，从光自养转向渗透），以响应营养和光环境的变化。从这项研究中获得的信息将对切萨皮克湾项目（CBP）、弗吉尼亚州环境质量部门和疾病控制中心有用。本项目将资助2名研究生。资金将支持ODU本科项目的研究，包括REU少数民族本科奖学金和培训（MUST）项目。一位来自霍尔-邦纳海洋科学少数民族博士学者项目的学者将作为该项目的一部分进行研究。ODU是一个为少数民族服务的机构，这个项目的成果将被纳入穆赫兰教授的本科和研究生课程。

The objectives of the proposed project are to determine key physiological and ecological processes that allow algal bloom species to out-compete other, co-occurring phytoplankton and bacteria. Shifts in phytoplankton community structure and increases in the frequency and duration of algal blooms in coastal waters around the world have been attributed to cultural eutrophication. For example, the Chesapeake Bay system has experienced decreases in species diversity and increases in the biomass of bloom producers over the last 50 years. Dissolved organic matter (DOM) may promote the growth of harmful algal species and initiate algal blooms. Algal bloom species can absorb and utilize dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) thereby contributing to eutrophication. Since DON and DOP also contain carbon (C), uptake can also provide a substantial heterotrophic subsidy to autotrophic photosynthesis. The ability of organisms to "swap" between autotrophic and heterotrophic metabolisms may offer clear evolutionary advantages as coastal areas become increasingly impacted by nutrient enrichment from anthropogenic activities. A major limitation to understanding algal blooms and ecological impacts of shifts in community structure is the lack of basic knowledge on the physiology of dinoflagellates and other bloom-forming organisms. The proposed research will contribute to the basic understanding of the physiological factors that allow algal mixotrophs to form monospecific blooms in the environment. The research will focus on field experiments in the lower Chesapeake Bay, near the mouth of the James River. Uptake of organic compounds by phytoplankton (relative to bacteria) will be evaluated in natural communities during bloom events. Autoradiography and antibiotic treatments will be used to manipulate species diversity and algal biomass. Nutrient enrichment bioassays will be conducted to determine competitive outcomes and shifts in trophic mode (e.g., shifting from photoautotrophy to osmotrophy) in natural assemblages in response to changes in the nutrient and light environment. The information derived from this study will be useful to the Chesapeake Bay Program (CBP) and the Virginia Department of Environmental Quality and Centers for Disease Control. This project will provide support for 2 graduate students. Funds will support research for ODU's undergraduate programs including the REU Minority Undergraduate Scholarship and Training (MUST) Program. A scholar from the Hall-Bonner Program for Minority Doctoral Scholars in Ocean Sciences will conduct research as part of this project. ODU is a minority serving institution and results from this project will be incorporated into the curriculum of undergraduate and graduate classes taught by Mulholland.