Collaborative Research: Trophodynamics of Myrionecta rubra and cryptophyte algae

合作研究：Myrionecta rubra 和隐藻的营养动力学

• 批准号: 1031344
• 负责人: Diane Stoecker
• 金额: $ 6.79万
• 依托单位: University of Maryland Center for Environmental Sciences
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1031344&HistoricalAwards=false
• 关键词: Collaborative; Research; Trophodynamics; Myrionecta; rubra

Myrionecta rubra (Mesodinium rubrum; Family Mesodiniidae) is a non-toxic red-tide forming ciliate in coastal and estuarine waters of the world. M. rubra possesses symbiotic organelles derived from cryptophyte algae, a ubiquitous group of algae in aquatic ecosystems. Because ciliates are usually considered protozoa, unicellular eukaryotes that have animal rather than plant-like qualities, M. rubra was long considered an enigma. Studies of phytoplankton ecology have frequently overlooked M. rubra, instead considering it part of the microzooplankton. In the last decade great progress has been made in understanding how the ciliate functions, largely due to the establishment of cultures. Recent studies have shown that one strain of M. rubra steal organelles (chloroplasts, mitochondria, and a nucleus) from cryptophyte prey, while another possesses stable (permanent) cryptophyte organelles. All strains of the ciliate, however, must feed on cryptophyte algae, either for acquiring organelles or growth factors. While we now have a greater understanding of the physiology of M. rubra, almost nothing is known regarding its ecological interactions with cryptophyte algae, bacteria, and potential predators in aquatic ecosystems. Cryptophyte algae are one of the major phytoplankton groups in Chesapeake Bay, contributing to primary production and acting as a major food item for a variety of organisms. M. rubra is widespread and seasonally abundant in Chesapeake Bay and its tributaries, and can reach red-tide concentrations in the spring and fall. Little is known regarding the genetic diversity of cryptophyte or M. rubra populations in Chesapeake Bay or other ecosystems.The objectives of this study are to determine the physical and chemical factors and biological interactions that regulate production of M. rubra and cryptophytes, and to characterize the range and seasonal patterns of genetic diversity of these organisms in Chesapeake Bay. Another goal is to determine the role of cryptophyte genetic diversity in the production of Myrionecta ciliates. Using oceanographic, physiological, and molecular approaches, the team of investigators proposes to execute the first large scale ecological studies of this unique and ecologically important ciliate, in order to understand its role in marine microbial food webs and to better predict its abundance and distribution. The Project is important for two reasons, 1) M. rubra can be a dominant member of the plankton in nearly all coastal ecosystems, yet its trophic role remains enigmatic and 2) cryptophyte algae play a pivotal role in the ecology of most estuarine and coastal ecosystems, yet they remain a "black box" of poorly characterized flagellates. Despite numerous reports of M. rubra red tides, we still have a rudimentary understanding of its mixotrophic role, as both alga and grazer, and how these strategies are balanced in natural food webs. The production of M. rubra, like many other mixotrophs in Chesapeake Bay and other coastal ecosystems, is linked to cryptophyte algal production. However, we are currently unable to predict ecosystem dynamics of M. rubra, due largely to our lack of knowledge of their cryptophyte prey selection, the spatial and temporal dynamics of cryptophyte production, and the effects of grazing pressure on bloom formation and termination. The Chesapeake Bay is an ideal location to perform this research because both M. rubra and cryptophytes are extremely abundant, their productivity is seasonally predictable in its timing and location, and sampling sites are easily accessible.This activity will be used to advance Ocean Science Literacy by educating the public about microbial diversity and microbial food web interactions. Results from this project will be broadly disseminated through scientific papers, workshop presentations, conferences, seminars, contributions to existing and new web sites, and discussions with the media. Undergraduates will participate in this project through the WHOI winter and summer research program. This proposal will also contribute to the professional development a young scientist.

红豆杉Myrionecta rubra(Mesoddium rubrum；Mesodiniidae)是一种在世界沿海和河口水域形成纤毛虫的无毒赤潮动物。红色微囊藻具有来自隐藻的共生细胞器，隐藻是水生生态系统中普遍存在的藻类。因为纤毛虫通常被认为是原生动物，即具有动物而不是植物特征的单细胞真核生物，所以鲁布拉支原体长期以来一直被认为是一个谜。对浮游植物生态的研究经常忽略了红色微藻，而是认为它是微型浮游动物的一部分。在过去的十年里，在了解纤毛虫的功能方面取得了很大的进展，这在很大程度上是由于文化的建立。最近的研究表明，一株红色微藻从猎物中窃取细胞器(叶绿体、线粒体和细胞核)，而另一株拥有稳定的(永久)隐芽细胞器。然而，所有种类的纤毛虫都必须以隐芽藻类为食，以获取细胞器或生长因子。虽然我们现在对红色微藻的生理学有了更多的了解，但关于它与水生生态系统中的隐芽藻类、细菌和潜在捕食者的生态相互作用几乎一无所知。隐藻是切萨皮克湾的主要浮游藻类之一，为初级生产力做出贡献，也是各种生物的主要食物。红色分支杆菌在切萨皮克湾及其支流分布广泛且季节性丰富，在春季和秋季可达到赤潮密度。关于切萨皮克湾或其他生态系统中隐芽植物或红曲霉种群的遗传多样性知之甚少，本研究的目的是确定控制红曲霉和隐芽植物生产的物理和化学因素以及生物相互作用，并描述切萨皮克湾这些生物遗传多样性的范围和季节格局。另一个目标是确定隐芽植物遗传多样性在纤毛虫生产中的作用。利用海洋学、生理学和分子生物学的方法，研究小组提议对这种独特的、具有生态重要性的纤毛虫进行首次大规模的生态学研究，以了解它在海洋微生物食物网中的作用，并更好地预测它的丰度和分布。该项目之所以重要，有两个原因，1)红色微藻可以是几乎所有沿海生态系统中的主要浮游生物成员，但其营养作用仍然是个谜；2)隐藻在大多数河口和沿海生态系统的生态中发挥着关键作用，但它们仍然是一个特征不佳的鞭毛虫的“黑匣子”。尽管有许多关于红色微藻赤潮的报道，但我们仍然对其作为藻类和食草动物的混合营养作用以及这些策略如何在自然食物网中平衡有一个初步的了解。与切萨皮克湾和其他沿海生态系统中的许多其他混合营养体一样，红色微囊藻的生产与隐芽藻类的生产有关。然而，我们目前无法预测红豆杉的生态系统动态，这主要是因为我们缺乏关于它们的隐芽猎物选择、隐芽植物生产的时空动态以及放牧压力对水华形成和终止的影响的知识。切萨皮克湾是进行这项研究的理想地点，因为红色微囊藻和隐芽植物极其丰富，它们的生产力在时间和地点上是季节性可预测的，而且采样点很容易到达。这项活动将通过教育公众了解微生物多样性和微生物食物网相互作用来提高海洋科学素养。该项目的成果将通过科学论文、讲习班介绍、会议、研讨会、对现有网站和新网站的贡献以及与媒体的讨论等方式广泛传播。本科生将通过世界卫生组织冬季和夏季研究计划参与这一项目。这项建议也将有助于青年科学家的职业发展。