Shunt or shuttle? Nutrient-driven biogeochemical consequences of diatom host-virus interactions

硅藻是一种微小的海洋藻类，构成了海洋食物网的基础，并产生了地球上约20%的氧气。自维多利亚时代以来，这些生物就受到人们的赞赏，它们通常被称为“海洋玻璃屋”，因为它们的细胞壁由二氧化硅或玻璃制成，结构复杂。当这些生物死亡时，与细胞相关的碳和其他元素可以被其他浮游植物回收再利用，或者因为玻璃比海水重，从海洋表面下沉而丢失。因此，硅藻对碳循环的贡献取决于促进循环的因素和刺激出口的因素之间的平衡。作为海洋中最丰富的实体，几十年来，病毒一直被认为是高效的回收者，通过阻止能量通过宿主死亡和裂解向食物链上游转移，起到了“分流”的作用。然而，有人认为，病毒也可能充当通往深海的“穿梭机”，刺激促进下沉的细胞过程。该项目正在测试这一新兴假设，并确定不同的营养制度如何通过对病毒感染动态和死亡的影响来影响硅藻的命运。考虑到目前正在寻求量化生态系统相互作用如何调节海洋碳输出的重大国家和国际倡议，这是特别及时的。该项目的结果有可能挑战硅藻病毒在碳循环中的典型作用，并改变对海洋中宿主-病毒相互作用的理解。该项目为女性海洋学家、研究生和本科生提供了关键的资金支持。拟议的实地考察利用了罗格斯大学和欧盟资助的一个项目，促进了与意大利那不勒斯安东·多恩动物学研究所的研究人员的持续合作。为了促进海洋素养，pi正在与罗格斯大学的教育和推广团队合作，利用“科学工具”（ToS）开展一系列青少年咖啡馆，重点关注碳循环、浮游植物和病毒，这是一系列教育视频和课程计划，旨在向代表性不足和服务不足的社区的初中、高中和本科生介绍核心科学实践。硅藻贡献了近40%的海洋初级生产力，主导着生物泵，由于硅基细胞壁的压舱特性，硅藻对碳输出的贡献不成比例。硅藻对碳封存的贡献是由上层海洋再矿化和下沉之间的平衡决定的，但我们仍然不能解释硅藻介导的出口的广泛时空变异性。作为海洋中数量最多的掠食性实体，病毒在塑造微生物生态系统和推动全球生物地球化学循环方面发挥着关键作用。该建议的前提是营养制度驱动硅藻宿主-病毒相互作用的生物地球化学后果。几十年来，病毒作为“分流器”的作用，通过宿主裂解将颗粒物质从较高的营养水平转移到溶解的部分，一直主导着微生物生态学和海洋病毒学。然而，病毒也可能充当“穿梭机”，通过刺激聚集和/或压舱物生产来促进碳输出，这一想法现在正在成为碳通量的潜在机制。该项目正在对多种硅藻宿主-病毒系统进行实验室研究，并对天然硅藻群落进行操控性研究，以比较病毒感染对促进下沉过程（矿物压载物生产和颗粒聚集）和刺激再矿化过程（细菌介导的硅藻颗粒有机物和二氧化硅的水解和随后的再矿化）的影响。综上所述，这项工作描述了在营养体制（特别是硅和铁限制）的生态生理背景下，这些截然相反的结果之间的相对平衡，最终阐明了病毒感染对海洋中硅藻有机质命运的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Diatoms are a type of microscopic marine algae that form the base of the ocean food web and generate about 20% of the oxygen on the planet. Admired since the Victorian age, these organisms are often referred to as the ‘glass houses of the sea’ because of the intricate architecture of their cell walls made of silicon dioxide, or glass. When these organisms die, the cellular-associated carbon and other elements can be either recycled and reused by other phytoplankton or, because glass is heavier than seawater, lost by sinking out of the surface ocean. Thus, the contribution diatoms make to carbon cycling is dictated by the balance between the factors that facilitate recycling and those that stimulate export. As the most abundant entity in the ocean, viruses have, for decades, been characterized as efficient recyclers, acting as ‘shunts’ by preventing the transfer of energy up the food chain through host mortality and lysis. However, it has been suggested that viruses may also act as ‘shuttles’ to the deep ocean, stimulating cellular processes that facilitate sinking. This project is testing this emerging hypothesis and determining how different nutrient regimes influence the fate of diatoms through impacts on viral infection dynamics and death. This is particularly timely given major national and international initiatives currently seeking to quantify how ecosystem interactions regulate carbon export in the ocean. Results of this project have the potential to challenge the canonical role of diatom viruses in carbon cycling and transform the understanding of host-virus interactions in the ocean. This project provides critical funding support for a soft-money, underrepresented, female oceanographer, as well a graduate student and undergraduates. Proposed fieldwork leverages a Rutgers and European Union-funded project, fostering ongoing collaborations with researchers at the Stazione Zoologica Anton Dohrn in Naples, Italy. To facilitate ocean literacy, the PIs are working with the Rutgers’ Education and Outreach team to conduct a series of Teen Cafes focused on carbon cycling, phytoplankton, and viruses utilizing the ‘Tools of Science’ (ToS), a series of educational videos and lesson plans designed to introduce middle, high school, and undergraduate students in underrepresented and underserved communities to core scientific practices. Diatoms contribute almost 40% of marine primary productivity, dominating the biological pump and disproportionately contributing to carbon export due to the ballasted nature of a silica-based cell wall. The contribution of diatoms to carbon sequestration is dictated by the balance between upper ocean remineralization and sinking, yet we still cannot explain widespread spatio-temporal variability in diatom-mediated export. As the most abundant predatory entities in the ocean, viruses play a critical role in shaping microbial ecosystems and driving global biogeochemical cycles. The premise of this proposal is that nutrient regimes drive the biogeochemical consequences of diatom host-virus interactions. For decades, the role of viruses as ‘shunts’, redirecting particulate matter away from higher trophic levels and into the dissolved fraction through host lysis, has dominated microbial ecology and marine virology. However, the idea that viruses may also act as ‘shuttles’, facilitating carbon export by stimulating aggregation and/or ballast production, is now emerging as a potential mechanism for carbon flux. This project is conducting laboratory-based studies on diverse diatom host-virus systems and manipulative studies on natural diatom communities to compare the impact of viral infection on processes that facilitate sinking – mineral ballast production and particle aggregation – to those that stimulate remineralization – bacterial-mediated hydrolysis and subsequent remineralization of diatom particulate organic matter and silica. Taken together, this work is characterizing the relative balance between these diametrically opposing outcomes within the ecophysiological context of nutrient regime (specifically, silicon and iron limitation), ultimately elucidating the impact of viral infection on the fate of diatom organic matter in the ocean.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.