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

Salps是一种独特的远洋动物，体型从几毫米到二十多厘米不等，身体呈凝胶状，可以形成由许多相连的个体组成的长链。这些海洋生物就像海洋真空吸尘器，对浮游植物的摄食率高得令人难以置信，对于它们这样大小的消费者来说，不同寻常的是，它们是细菌大小的猎物。这种快速的摄食和盐藻形成密集水华的趋势，使它们能够将大量的猎物碳从表面转移到深海，导致二氧化碳从大气中清除。然而，盐类通常被认为是食物链中的营养死胡同，而不是一个环节，因为它们本身不被消费，因为它们胶状的身体比共生的甲壳类猎物营养更少。此外，据推测，由于气候变化，盐碱地的数量将会增加。这一建议解决了这些问题：1)盐生植物主要是与甲壳类动物竞争(正如在流行的范例中那样)，还是它们是单细胞原生动物的竞争对手，单细胞原生动物是小型浮游植物的主要捕食者？2)盐藻水华是否提高了从微小浮游植物到营养不良海洋区域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外联举措，包括开发为期一周的生物海洋学沉浸式高中课程，以及将为佛罗里达州塔拉哈西的“学校科学家”方案服务的教育模块。人们通常认为，盐碱地是一个营养池。然而，这一想法是在发现原生动物(而不是甲壳类)是开放海洋中的主要食草动物之前发展起来的，并因难以识别鱼肠道中的胶状盐分而产生偏见。最近的研究表明，在各种鱼类和海鸟的肠道中都发现了盐分，当甲壳类动物丰度较低时，盐分是一种容易获得的猎物来源。这项提议试图通过对比新西兰西部查塔姆海隆附近以盐分为主和不含盐分的水域来量化食物网络流动，在那里，盐华是一种可预测的现象。该提案将利用新西兰合作者在拉格朗日实验期间获得的关于盐分丰度、大宗放牧影响和生物地球化学意义的数据。该提案将确定1)特定分类和大小的浮游植物生长速度测量，2)特定分类和大小的原生动物和盐分捕食率的测量，3)对中游动物氨基酸的复合特定同位素分析，以量化盐类、Hyperiid两足类和其他甲壳类动物的营养位置，4)沉积物捕捉器，以量化浮游动物身体的下沉速度，以及5)线性反向生态系统模拟综合。这一受限的生态系统模型的次生生产力和营养流量将与相似特征地区(加州洋流、哥斯达黎加穹顶和墨西哥湾)中以甲壳类为主和微生物圈为主的生态系统进行比较。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.