Collaborative Research: Diel dynamics of dissolved organic matter production and remineralization as a driver of coral reef nutrient recycling

合作研究：溶解有机物产生和再矿化的昼夜动态作为珊瑚礁养分循环的驱动力

• 批准号: 1949059
• 负责人: Linda Wegley Kelly
• 金额: $ 29.92万
• 依托单位: San Diego State University Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-01 至 2021-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1949059&HistoricalAwards=false
• 关键词: Collaborative; Research; Diel; dynamics; dissolved

This project develops a core understanding of diel microbial ecology and biogeochemistry in coral reef ecosystems. It contextualizes how crucial nutrient recycling processes vary across gradients of coral cover and nutrient availability, two factors highlighted as the main drivers of reef decline in the Anthropocene, making the results useful to managers seeking to enhance ecosystem-based approaches to reef restoration. The investigators are collecting diel measurements of microbial and biogeochemical processes at coral reefs around Mo’orea at the Long Term Ecological Research site there (MCR-LTER). They are using established spatial gradients of benthic cover, from coral to macroalgal dominance, and nutrient inputs. Overall the research improves our understanding of how these key environmental factors influence diel microbe-DOM interactions and nutrient recycling. The ongoing macroalgal phase shifts observed at Mo’orea are hypothesized to be related to nutrient pollution, and this work directly informs understanding of how these changes are impacting nutrient cycling in the reefs of Mo’orea. The training of several undergraduate students and two graduate students, one in Biology and one in Oceanography is shared between two minority serving institutions of higher education. The project also supports active outreach programs with the Ocean Discovery Institute focused on engaging underrepresented high school students in ocean-oriented careers in San Diego, and with the UH College Sea Grant Program to support coral reef resilience initiatives locally in Hawai‘i.Coral reefs exhibit some of the highest rates of primary production and decomposition of any ecosystem type yet persist in some of the most oligotrophic waters on the planet, implying tight recycling of macronutrients through organic matter. The last half century of work on the biogeochemistry of reefs have highlighted this bacterial decomposition of organic matter as a likely mechanism for maintaining nutrient retention and reef productivity. This project applies modern metagenomics and untargeted metabolomics to test clearly defined hypotheses of how diel microbe-DOM interactions drive nutrient recycling and retention in reefs. The investigators are first resolving coupled in situ diel dynamics of organic and inorganic C, N and P (using bulk elemental and spectroscopic methods), microbial abundances and population structures (using DNA sequencing and flow cytometry) and the chemical composition of DOM (using untargeted tandem mass spectrometry) in multiple reef habitats across a gradient of benthic cover and nutrient availability. These patterns inform the second in situ diel sampling campaign resolving the dynamic coupling of metabolic pathways (using metagenomics), exoenzymatic activity (using transcriptomics and enzyme assays) and transformations of specific metabolites (tracked via molecular networking) to distill common mechanisms of microbial organic matter decomposition that play a role in nutrient cycling. This project is being conducted within the Moorea Coral Reef Long Term Ecological Research program, leveraging a wealth of time series data on multiple reef habitats as well as contextualizing our in situ sampling with ongoing physical, geochemical and biological monitoring programs. By integrating cutting edge molecular approaches with well-established techniques in field ecology and microbial oceanography, this research program identifies key microbial and molecular players in the nutrient decomposition and remineralization processes long hypothesized to be central to maintaining healthy reefs.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.

该项目加深了对珊瑚礁生态系统中昼夜微生物生态学和生物地球化学的核心了解。它阐述了重要的养分循环过程如何随着珊瑚覆盖和养分可用性梯度的变化而变化，这两个因素被强调为人类世珊瑚礁衰退的主要驱动因素，使研究结果对寻求加强基于生态系统的珊瑚礁恢复方法的管理者有用。研究人员正在长期生态研究站点（MCR-LTER）收集莫雷阿周围珊瑚礁微生物和生物地球化学过程的昼夜测量数据。 他们正在利用既定的底栖覆盖空间梯度，从珊瑚到大型藻类的优势，以及养分输入。总体而言，这项研究提高了我们对这些关键环境因素如何影响昼夜微生物-DOM 相互作用和养分循环的理解。据推测，在莫雷阿岛观察到的正在进行的大型藻类相变与营养物污染有关，这项工作直接有助于了解这些变化如何影响莫雷阿岛珊瑚礁的营养物循环。几名本科生和两名研究生（一名生物学和一名海洋学）的培训由两所少数民族高等教育机构共同承担。该项目还支持与海洋探索研究所的积极外展计划，重点是让圣地亚哥代表性不足的高中生从事以海洋为导向的职业，并与夏威夷大学学院海洋资助计划一起支持夏威夷当地的珊瑚礁复原力计划。珊瑚礁在任何生态系统类型中表现出最高的初级生产力和分解率，但仍存在于一些最贫营养的水域中。 地球，这意味着大量营养素通过有机物进行紧密循环。过去半个世纪对珊瑚礁生物地球化学的研究强调了有机物的细菌分解是维持养分保留和珊瑚礁生产力的可能机制。该项目应用现代宏基因组学和非靶向代谢组学来测试关于昼夜微生物与 DOM 相互作用如何驱动珊瑚礁中养分循环和保留的明确假设。研究人员首先解决了跨底栖覆盖和养分可用性梯度的多个珊瑚礁栖息地中有机和无机 C、N 和 P（使用散装元素和光谱方法）、微生物丰度和种群结构（使用 DNA 测序和流式细胞术）以及 DOM 化学成分（使用非目标串联质谱法）的原位昼夜动力学耦合问题。这些模式为第二次原位昼夜采样活动提供了信息，解决了代谢途径（使用宏基因组学）、外酶活性（使用转录组学和酶测定）和特定代谢物的转化（通过分子网络跟踪）的动态耦合，以提炼在营养循环中发挥作用的微生物有机物分解的常见机制。该项目是在莫雷阿岛珊瑚礁长期生态研究计划内进行的，利用多个珊瑚礁栖息地的大量时间序列数据，并将我们的原位采样与正在进行的物理、地球化学和生物监测计划结合起来。通过将尖端分子方法与野外生态学和微生物海洋学领域成熟的技术相结合，该研究项目确定了养分分解和再矿化过程中的关键微生物和分子参与者，长期以来，这些过程被认为是维持健康珊瑚礁的核心。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。