Collaborative Research: Trophodynamics of Myrionecta rubra and cryptophyte algae

褐毛绵虫（Mesodinium rubrum; Mesodiniidae）是一种无毒的红潮形成纤毛虫，分布在世界沿岸和河口水域。M. rubra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一组藻类。因为纤毛虫通常被认为是原生动物，单细胞真核生物，具有动物而不是植物的特性，所以长时间以来，红毛纤毛虫一直被认为是一个谜。对浮游植物生态学的研究经常忽略了红支原体，而认为它是微型浮游动物的一部分。在过去的十年里，人们在理解纤毛虫的功能方面取得了很大的进展，这主要是由于文化的建立。最近的研究表明，一种菌株从隐生植物猎物那里窃取细胞器（叶绿体、线粒体和细胞核），而另一种菌株拥有稳定的（永久的）隐生植物细胞器。然而，所有纤毛虫菌株都必须以隐藻为食，以获取细胞器或生长因子。虽然我们现在对M. rubra的生理学有了更深入的了解，但关于它与水生生态系统中隐藻、细菌和潜在捕食者的生态相互作用，我们几乎一无所知。隐藻是切萨皮克湾主要的浮游植物群之一，对初级生产有贡献，是多种生物的主要食物。红藻在切萨皮克湾及其支流分布广泛，季节性丰富，在春季和秋季可达到红潮浓度。人们对切萨皮克湾或其他生态系统中隐生植物或M. rubra种群的遗传多样性知之甚少。本研究的目的是确定在切萨皮克湾调节红m.b rubra和隐生植物的生产的物理和化学因素和生物相互作用，并表征这些生物的遗传多样性的范围和季节模式。另一个目标是确定隐生植物遗传多样性在肉苁蓉生产中的作用。利用海洋学、生理学和分子方法，研究小组建议对这种独特的、具有重要生态意义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)在几乎所有的沿海生态系统中，M. rubra是浮游生物的主要成员，但它的营养作用仍然是一个谜；2)在大多数河口和沿海生态系统中，隐藻起着关键作用，但它们仍然是鞭毛虫的“黑盒子”。尽管有许多关于红藻赤潮的报道，我们仍然对它的混合营养作用有初步的了解，既是藻类又是食草动物，以及这些策略如何在自然食物网中平衡。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型生物一样，M. rubra的生产与隐藻的生产有关。然而，由于我们缺乏对其隐生植物猎物选择、隐生植物生产的时空动态以及放牧压力对开花形成和终止的影响的了解，目前我们还无法预测红毛杨的生态系统动态。切萨皮克湾是进行这项研究的理想地点，因为红m.b rubra和隐生植物都非常丰富，它们的生产力在时间和地点上都是季节性可预测的，而且采样地点很容易到达。这项活动将通过教育公众有关微生物多样性和微生物食物网相互作用的知识来提高海洋科学素养。该项目的成果将通过科学论文、讲习班演讲、会议、研讨会、对现有和新网站的投稿以及与媒体的讨论等方式广泛传播。本科生将通过WHOI冬季和夏季研究计划参与本项目。这一建议也将有助于青年科学家的专业发展。

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.