Collaborative Research: Quantifying the impact of oxylipin chemical signaling on microbial community dynamics and biogeochemical cycling

硅藻是一种真核浮游植物，占全球光合作用的25%。许多种类的硅藻在营养限制、放牧伤害和病毒感染等应激环境下产生称为氧化脂素的化学信号。这些化学信号对构成海洋微生物食物网的许多生物都是有害的，比如其他真核浮游植物、以浮游植物为食的微型浮游动物和桡足类动物，以及自由生活的细菌。然而，与颗粒相关的细菌群落受到低剂量的氧化脂素的刺激，硅藻可以利用这些化学信号在它们之间就即将到来的压力进行交流。因为这些微生物食物网在地球的碳循环中起着至关重要的作用，这些生态系统最终支持渔业，所以了解硅藻华在生产上升流地区旋转和崩溃时化学信号所起的作用非常重要。在这里，研究人员提出了一个实地考察，通过一系列的甲板孵化来研究氧化脂素对加州洋流生态系统中群落动态的影响。该团队还提出了一系列以实验室为基础的捕食者-猎物研究，通过用显微录像记录行为来量化氧化脂素对微型浮游动物食草动物的影响。将解决的主要问题包括：1)在开花过程中，氧脂素的浓度和多样性是如何变化的？2)氧脂素信号对群落动态的净影响是什么？3)氧脂如何影响碳输出和养分循环（N， P, Si）？在本基金存续期间开展的外展活动的主要目标是向年轻人介绍微生物海洋学，培训多样化的海洋学工作人员，并创建可以在本基金存续后通过探究获取的内容。为了实现这一目标，本科生和研究生的科学家们在这个项目中通过直接参与计划中的巡航、在实验室、在教室通过虚拟直播的巡航活动和面对面的教学进行培训。其中一些学生是专门从增加代表性不足群体参与的项目中招募的。该项目还使用巡航数据来设计数据分析教程和研讨会，以吸引更广泛的科学界。来自当地城市地区的初高中学生也正在接受在科德角附近沿海水域进行教育一日游的培训。目前正在为8-12年级的教室开发与该项目工作相关的课程。这是第一个研究在溶解、细胞和碎屑（即海洋雪）馏分中产生的氧脂素的全部多样性的研究。这是第一个同时评估生态系统中氧化脂生成的原位驱动因素（营养胁迫、放牧和病毒感染）的研究。该项目也是第一个全面描述东部边界流中藻华过程中氧脂质浓度和多样性的项目。该项目的最终目标是了解氧脂素介导的信号如何影响碳的命运，因此该团队将在整个实地活动中监测出口效率、净初级生产力、细菌生产力和营养循环。该项目增加了相对较少的来自下沉颗粒群落和海洋脂质组数据集的公共存储库中的亚转录组数据集。拉格朗日研究产生的数据可以用来提出更多关于表层和深海之间的连通性、群落演替和水华的地球化学演化的一般性问题。最后，本研究通过同时评估浮游微动物在存在外源氧脂素和提供高氧脂素和低氧脂素的猎物时的放牧率、选择和行为，改变了我们对化学信号如何影响放牧行为和氧脂素放牧威慑机制的集体理解。最先进的微型摄像技术可以可视化和量化微型浮游动物的放牧行为，该系统将适用于海中自然群落的测量。本项目由海洋科学部生物和化学海洋学项目资助。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 eukaryotic phytoplankton that are responsible for ~25% of photosynthesis globally. Many species of diatoms produce chemical signals called oxylipins under stressful circumstances such as nutrient limitation, wounding due to grazing, and viral infection. These chemical signals are detrimental to many organisms that make up microbial food webs in the ocean, like other eukaryotic phytoplankton, microzooplankton and copepods that graze on phytoplankton, and free-living bacteria. However, particle-associated bacterial communities are stimulated by low doses of oxylipins, and diatoms can use these chemical signals to communicate amongst themselves about impending stress. Because these microbial food webs play a critical role in the Earth’s carbon cycle and these ecosystems ultimately support fisheries, it is important to understand the role chemical signaling plays as diatom blooms spin up and crash in productive upwelling regions. Here the investigators propose a field expedition with a series of deck-board incubations to study the effects of oxylipins on community dynamics in the California Current Ecosystem. The team also proposes a series of laboratory-based predator-prey studies to quantify the effects of oxylipins on microzooplankton grazers by documenting behavior with microvideography. The major questions that will be addressed include: 1) how does the concentration and diversity of oxylipins change over the course of a bloom? 2) what is the net impact of oxylipin signaling on community dynamics? 3) how do oxylipins impact carbon export and nutrient recycling (N, P, Si)? Outreach activities undertaken during the lifetime of this grant have the primary goals of introducing young people to microbial oceanography, training a diverse oceanographic workforce, and creating content that can be accessed by inquiring minds after the lifetime of this grant. To accomplish this, undergraduate and graduate scientists are being trained during this project through direct participation on the planned cruise, in the lab, and in classrooms through virtual live-streaming cruise activities and in-person teaching. Some of these students are recruited specifically from programs that increase participation from underrepresented groups. This project also uses cruise data to design data-analysis tutorials and workshops in order to engage the broader science community. Middle and high school students from local urban areas are also being trained on educational day trips in the coastal waters around Cape Cod. A curriculum is being developed for grade 8-12 classrooms related to the work of this project. This is the first study to profile the full diversity of oxylipins produced across dissolved, cellular, and detrital (i.e., marine snow) fractions. It is the first study to simultaneously assess in situ drivers of oxylipin production (nutrient stress, grazing, and viral infection) within an ecosystem. The project is also be the first to fully characterize oxylipin concentrations and diversity over the course of a bloom within an Eastern Boundary Current. The ultimate goal of this project is to understand how oxylipin-mediated signaling impacts the fate of carbon, so the team will be monitoring export efficiency, net primary productivity, bacterial productivity, and nutrient recycling throughout the field campaign. This project adds to the relatively small number of metatranscriptomic datasets from sinking particle communities and marine lipidomic datasets available in public repositories. The data generated by the Lagrangian Study can be used to ask more general questions about connectivity between the surface and deep ocean, community succession, and the geochemical evolution of blooms. Finally, the proposed research transforms our collective understanding of how chemical signaling impacts grazing behavior and the mechanism of oxylipin grazing deterrence by simultaneously assessing grazing rates, selection, and behavior of microzooplankton in the presence of exogenous oxylipins and when offered high and low oxylipin-producing prey. State-of-the-art microvideography visualizes and quantifies microzooplankton grazing behaviors, and the system will be adapted for measurements of natural communities at sea. This project is funded by the Biological and Chemical Oceanography Programs in the Division of Ocean Sciences.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.