Biogeochemical and Ecological Impacts of Amphipod Circoviruses in Benthic Habitats

概述：该项目将通过研究病毒流行率的实验梯度和添加培养病毒来研究圆环病毒如何影响底栖片足类动物的食草/碎食率。要测试的假设是： H1：圆环病毒导致受感染的片足类宿主的碎食和草食性减少； H2：环病毒对片足类动物的影响导致沉积物细菌的生长速度降低，沉积物微生物的细胞外纤维素活性降低，以及从沉积物到上覆水域的氧化无机营养物通量减少； H3：圆环病毒对其宿主的营养质量产生负面影响。这些假设将通过沉积物-水中生态系统实验来测试，以评估圆环病毒对水生植被破坏的影响，以及随后对生物地球化学的影响，包括细菌产生、减少的氮流入上覆水域以及溶解有机碳的产生。最后，该项目将通过检查圆环病毒流行率从高到低的端足类种群和实验感染的端足类的元素比率，研究圆环病毒如何影响端足类的营养质量。这三种方法的数据将用于形成圆环病毒如何影响沉积物栖息地的底栖食物网和生物地球化学循环的模型。本研究重点关注两种对生态系统功能至关重要的生态敏感片脚类动物中的圆环病毒：Diporeia（密歇根湖）和 Peramphithhoe femorata，前者的丰度在过去 20 年中在五大湖中经历了急剧下降，后者是美国西海岸受到环境威胁的巨藻巨藻的主要消费者。然而，大多数研究都集中在真核微生物的噬菌体和病毒上。后生动物是底栖生物地球化学的重要驱动因素，它们引起缺氧沉积物的生物灌溉、再悬浮、颗粒物的沉降，促进营养物从沉积物到上覆水域的流动，并可能影响沉积物反硝化等海洋尺度过程。圆环病毒已被确定为甲壳动物病毒组合的常见成分，它们与宿主死亡率和种群下降密切相关，并且培养的圆环病毒会导致节肢动物细胞死亡。因此，迫切需要研究病毒如何影响其甲壳类宿主的生态，以及这些影响又如何影响生态系统功能。端足类动物是底栖栖息地的重要表层动物组成部分，它们消耗沉积的颗粒物和水生植被，进而影响其通过微生物降解转化为溶解的有机物。反过来，它们的摄食活动刺激了底栖矿化速率，并被更高的营养层消耗。因此，片脚类动物将沿海和湖泊栖息地的微生物与大型食物网联系起来。该项目研究感染端足类动物的圆环病毒如何影响底栖生态系统中的碳通量，作为后生动物病毒如何影响水生生态系统的生物地球化学的模型。该研究将深入了解病毒如何影响水生生物地球化学，开辟底栖生态系统中后生动物病毒的新研究领域。更广泛的影响：该项目旨在纳入三项更广泛的影响活动。首先，纽菲尔德高中（纽约州纽菲尔德）和奥奈达湖地区高中的科学教师将直接让高需求学生加入研究团队，进行实验和实验室分析，最终向同侪小组展示他们的研究活动。其次，它将通过暑期在康奈尔生物野外站实习的方式吸引本科生，并在康奈尔学年期间吸引本科生研究人员参与实验并磨练科学演示的技能。第三，它将开发广泛的基于网络的推广工具，包括一个网站（包含实验的实时视图）以及针对公众和 K-12 学生的社交媒体页面。最后，拟议的工作将深入了解脆弱水生生态系统的生态。

Overview: This project will investigate how circoviruses influence the herbivory/detritivory rates of benthic amphipods through the study of an experimental gradient of viral prevalence and by addition of cultivated viruses. The hypotheses to be tested are: H1: Circoviruses cause decreased detritivory and herbivory by infected amphipod hosts; H2: Circoviral impacts on amphipods result in decreased growth rate of sediment bacteria, decreased extracellular cellulose activity of sediment microorganisms, and decreased fluxes of oxidized inorganic nutrients from sediments into overlying waters; H3: Circoviruses negatively impact the nutritional quality of their hosts. These hypotheses will be tested by conducting sediment-water mesocosm experiments to assess the impacts of circoviruses on aquatic vegetation breakdown, and subsequent impacts on biogeochemistry, including bacterial production, efflux of reduced N into overlying waters, and production of dissolved organic C. Finally, this project will examine how circoviruses influence the nutritional quality of amphipods by examining elemental ratios of amphipod populations from high to low circoviral prevalence and experimentally infected amphipods. Data from these three approaches will be used to form a model of how circoviruses influence benthic foodwebs and biogeochemical cycles in sediment habitats. This study focuses on circoviruses within two ecologically sensitive amphipods that are crucial to ecosystem function: Diporeia (in Lake Michigan), which has experienced dramatic decline in abundance over the last 20 years within the Great Lakes, and Peramphithoe femorata, which is a major consumer of the environmentally threatened giant kelp Macrocystis pyrifera on the US West Coast.Intellectual Merit: Decades of research have identified the importance of viruses in aquatic ecology and biogeochemistry.However, most studies have focused on bacteriophage and viruses of eukaryotic microorganisms. Metazoa are important drivers of benthic biogeochemistry, where they cause bioirrigation of anoxic sediments, resuspension, settlement of particulate matter, facilitating nutrient fluxes from sediments to overlying waters, and potentially influencing ocean-scale processes like sediment denitrification. Circoviruses have been identified as a common constituent of crustacean viral assemblages, where they are well correlated with host death rates and population decline, and cultivated circoviruses cause death of arthropod cells. There is therefore a strong need to investigate how viruses impact the ecology of their crustacean hosts, and how in turn those impacts influence ecosystem function. Amphipods are important epifaunal constituents of benthic habitats, where they consume settled particulate matter and aquatic vegetation, which in turn influences its conversion to dissolved organic matter through microbial degradation. In turn their feeding activities stimulate benthic mineralization rates, and they are consumed by higher trophic levels. Therefore, amphipods link microbial to macrobial food webs in coastal and lake habitats. This project investigates how circoviruses infecting amphipods influence the flux of C through benthic ecosystems as a model of how viruses of metazoa influence biogeochemistry of aquatic ecosystems. The research will provide insight into how viruses influence aquatic biogeochemistry, opening up a new area of research into metazoan viruses in benthic ecosystems.Broader Impacts: The project has been designed to incorporate three broader impact activities. First, it will involve science teachers at the Newfield High School (Newfield, NY) and Oneida Lake Region high schools to directly involve and integrate high needs students into the research team to conduct experiments and laboratory analyses, culminating in presentation of their research activities to their peer group. Second, it will engage undergraduate students through summer internships at the Cornell Biological Field Station, and undergraduate researchers during the school year at Cornell to participate in the experiments and hone skills in scientific presentation. Third, it will develop extensive web-based outreach tools, including a website (incorporating live views of experiments), and social media pages targeting the general public and K-12 students. Finally, the proposed work will provide insight into the ecology of vulnerable aquatic ecosystems.