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，使藻华物种竞争其他，共同发生的浮游植物和细菌。 世界各地沿海沃茨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被归因于文化性富营养化。 例如，在过去50年里，切萨皮克湾系统的物种多样性减少，水华生产者的生物量增加。 溶解有机物（DOM）可以促进有害藻类的生长，引发水华. 水华藻类对水体中溶解性有机氮（DON）和溶解性有机磷（DOP）的吸收和利用是导致水体富营养化的重要原因。 由于DON和DOP也含有碳（C），因此吸收也可以为自养光合作用提供实质性的异养补贴。 随着沿海地区越来越多地受到人类活动造成的营养富集的影响，生物体在自养和异养代谢之间“交换”的能力可能提供明显的进化优势。 了解藻类水华和群落结构变化的生态影响的一个主要限制是缺乏对甲藻和其他水华形成生物的生理学的基本知识。该研究将有助于对藻类混养体在环境中形成单种水华的生理因素的基本了解。这项研究将集中在詹姆斯河口附近的切萨皮克湾下游的实地实验。 浮游植物（相对于细菌）对有机化合物的吸收将在水华期间在自然群落中进行评估。 放射自显影和抗生素治疗将用于操纵物种多样性和藻类生物量。将进行营养物富集生物测定，以确定竞争结果和营养模式的转变（例如，从光自养向光自养的转变）。 从这项研究中获得的信息将是有用的切萨皮克湾计划（CBP）和弗吉尼亚州环境质量部和疾病控制中心。该项目将为2名研究生提供支持。 资金将支持ODU的本科课程的研究，包括REU少数民族本科奖学金和培训（MUST）计划。 作为该项目的一部分，海洋科学少数民族博士生霍尔-邦纳项目的一名学者将进行研究。 ODU是一个少数民族服务机构，该项目的成果将纳入Mulholland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.