Collaborative Research: Quantifying trophic roles and food web ecology of salp blooms of the Chatham Rise

海鞘是一种独特的开放海洋动物，大小从几毫米到20多厘米不等，有一个胶状（果冻状）的身体，可以形成许多连接个体的长链。这些海洋生物就像海洋吸尘器一样，对浮游植物的摄取率高得令人难以置信，而且对于它们体型的消费者来说，更小的细菌大小的猎物是不寻常的。这种快速的进食和海带形成密集藻华的倾向，使它们能够将大量的猎物碳从表面转移到深海，从而从大气中去除二氧化碳。然而，在食物网中，海带通常被认为是营养的死胡同，而不是一个环节，因为假设它们自己不被消耗，因为它们凝胶状的身体比共生的甲壳类猎物营养更少。与此同时，据推测，由于气候变化，salp的数量正在增加。这一提议解决了以下问题：1)海带主要是与甲壳类动物竞争（就像普遍的范例那样），还是与主要以小型浮游植物为食的单细胞原生生物竞争？2)在营养贫乏的海洋地区，海藻华是否提高了从微小浮游植物到渔业生产的食物网途径的效率？该项目将支持一名研究生的跨学科教育，该研究生将学习生物和化学海洋学领域的建模和实验室技术，并促进美国和新西兰科学家之间的国际合作。此外，还计划了几项教育和推广活动，包括开发为期一周的沉浸式生物海洋学高中课程，以及为佛罗里达州塔拉哈西的“学校里的科学家”项目服务的教育模块。然而，这个想法是在发现原生生物（而不是甲壳类动物）是开放海洋中主要的食草动物之前发展起来的，并且由于难以识别鱼内脏中的胶状海藻而存在偏见。最近的研究表明，海鞘存在于多种鱼类和海鸟的内脏中，当甲壳类动物的丰度较低时，海鞘是一种现成的猎物来源。该方案旨在通过新西兰西部查塔姆海隆起附近以海藻为主和不以海藻为主的水域对比，量化食物网的流动，在那里，海藻大量繁殖是可预测的现象。该提案将利用先前在新西兰合作者进行的拉格朗日实验中获得的关于salp丰度、大规模放牧影响和生物地球化学意义的数据。该提案将确定1)特定分类群和特定大小的浮游植物生长速率测量，2)特定分类群和特定大小的原生动物和salp放牧速率测量，3)中浮游动物氨基酸的复合特定同位素分析，以量化salp，半纲片脚类和其他甲壳类动物的营养地位，4)沉积物陷阱，以量化浮游动物尸体下沉速率，5)线性逆生态系统建模合成。这种良好约束的生态系统模型的二次生产和营养流将与相似特征地区（加利福尼亚海流、哥斯达黎加巨丘和墨西哥湾）的甲壳类和微生物环主导的生态系统进行比较。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。

Salps are unique open-ocean animals that range in size from a few millimeters to greater than twenty centimeters, have a gelatinous (jelly-like) body, and can form long chains of many connected individuals. These oceanic organisms act as oceanic vacuum cleaners, having incredibly high feeding rates on phytoplankton and, unusual for consumers of their size, smaller bacteria-sized prey. This rapid feeding and the salps' tendency to form dense blooms, allows them move substantial amounts of prey carbon from the surface into the deep ocean, leading to carbon dioxide removal from the atmosphere. However, salps are often considered a trophic dead-end, rather than a link, in the food web due to the assumption that they themselves are not consumed, since their gelatinous bodies are less nutritious than co-occurring crustacean prey. Along with this, salp populations are hypothesized to be increasing due to climate change. This proposal addresses these questions: 1) Do salps compete primarily with crustaceans (as in the prevailing paradigm) or are they competitors of single-celled protists, which are the dominant grazers of small phytoplankton? 2) Do salp blooms increase the efficiency of food-web pathways from tiny phytoplankton to fisheries production in nutrient-poor ocean regions? This project will support the interdisciplinary education of a graduate student who will learn modeling and laboratory techniques in the fields of biological and chemical oceanography and stimulate international collaborations between scientists in the United States and New Zealand. Additionally, several Education and Outreach initiatives are planned, including development of a week-long immersive high school class in biological oceanography, and education modules that will serve the "scientists-in-the schools" program in Tallahassee, FL.It is commonly assumed that salps are a trophic sink. However, this idea was developed before the discovery that protists (rather than crustaceans) are the dominant grazers in the open ocean and was biased by the difficulty of recognizing gelatinous salps in fish guts. More recent studies show that salps are found in guts of a diverse group of fish and seabirds and are a readily available prey source when crustacean abundance is low. This proposal seeks to quantify food web flows through contrasting salp-dominated and salp-absent water parcels near the Chatham Rise off western New Zealand where salp blooms are a predictable phenomenon. The proposal will leverage previously obtained data on salp abundance, bulk grazing impact, and biogeochemical significance during Lagrangian experiments conducted by New Zealand-based collaborators. The proposal will determine 1) taxon- and size-specific phytoplankton growth rate measurements, 2) taxon- and size-specific protozoan and salp grazing rate measurements, 3) compound specific isotopic analysis of the amino acids of mesozooplankton to quantify the trophic position of salps, hyperiid amphipods, and other crustaceans, 4) sediment traps to quantify zooplankton carcass sinking rates, and 5) linear inverse ecosystem modeling syntheses. Secondary production and trophic flows from this well-constrained ecosystem model will be compared to crustacean-dominated and microbial loop-dominated ecosystems in similarly characterized regions (California Current, Costa Rica Dome, and Gulf of Mexico).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.