Collaborative Research: From hot to cold in the dark - shifts in seafloor massive sulfide microbial communities as physical and geochemical conditions change after venting ceases

海底巨量硫化物（SMS）的海底热液喷口分布在89000公里长的洋中脊、海底火山和位于海洋构造板块边界的弧后盆地。活性热液喷口硫化物烟囱是深海生物多样性和生产力的热点，也是潜在的金属资源。虽然大量的工作都集中在了解生物群落的多样性和与活跃的SMS排放相关的地球化学上，但对于一旦SMS排放停止后与之相关的生物群落知之甚少。此外，在烟囱内微生物群落和流体地球化学发生重要演替的过程中，烟囱内微生物群落和流体地球化学发生了从活跃到不活跃的转变。这个跨学科的项目将通过从东太平洋北纬9度的单个喷口收集多个活跃的SMS样本来创建和采样这个过渡期，并允许它们在海底过渡到不活跃状态，模拟喷口的结束，同时考虑到喷口停止的确切时间，这在采样自然形成不活跃的SMS时是不可能的。微生物群落多样性和代谢将与活性、过渡和非活性硫化物的大量和精细地质测量同时进行分析。这种海底实验和分析方法将提供微生物群落、生物地球化学转化速率和地质条件如何随着SMS从热的、活跃的排气到冷的、不活跃的排气转变的知识。6-8年级的学生将通过研究巡航“船到岸”的互动和交流，为教育工作者提供与STEM领域代表性不足的学生合作的邮轮后研讨会，以及与科学，工程，艺术和设计画廊（SEAD）合作，这是德克萨斯州布莱恩的一个社区和经济发展项目。但目前绝大多数的知识都集中在活跃的喷发矿床上。然而，在排气停止后，硫化物可以在海底持续存在数万年，使它们成为长寿的、全球丰富的微生物基质。近年来，研究发现不活跃火山喷发沉积物的微生物群落与活跃火山喷发沉积物的微生物群落明显不同，这表明微生物群落的演替，因此对深海生物多样性和生物地球化学的影响可能与活跃火山喷发沉积物不同。然而，不活跃结构的年龄通常是未知的，因此不可能估计这些变化发生的速度，以及硫化物矿物学和微生物群落共同发生的变化发生的速度。该项目将首次深入了解微生物和矿物学水平上SMS最初从活性转变为非活性时发生了什么。活性SMS将被取样并分析微生物群落组成、功能容量、基因表达和代谢率。将分析位于同一位置的子样品的孔隙度、体积和细尺度矿物学。这些活跃的SMS样本的子样本将留在海底孵化，并在几周或一年或更长时间后收集，并在收集时进行相同的分析。这将允许确定在初始过渡期间发生的微生物和矿物学变化，并与来自同一喷口场的较老的非活性SMS进行比较。将收集到的数据综合起来，形成一个生物、矿物学、孔隙度和孔隙分布演替的概念模型，说明喷口沉积物从活跃到不活跃的转变。该项目将填补关于热液生态系统的知识空白，并有可能改变目前对这些重要海底生物群落多样性和变化速度的认识。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。

Hydrothermal vents, which deposit seafloor massive sulfides (SMS), occur along the 89,000 km of mid-ocean ridges, submarine volcanoes, and backarc basins that occur at tectonic plate boundaries in the ocean. Active hydrothermal vent sulfide chimneys are hotspots of biodiversity and productivity in the deep ocean, as well as potential resources for metals. While significant effort has focused on understanding the diversity of biological communities and geochemistry associated with actively venting SMS, relatively little is known about the biological communities associated with SMS once venting ceases. Furthermore, little is known about the microbiological and geochemical changes that occur during the transition period from active to inactive, during which an important succession occurs in the microbial community and geochemistry of fluids within the chimney. This interdisciplinary project will create and sample this transition period by collecting multiple active SMS samples from individual vents at 9 degrees N East Pacific Rise and allowing them to transition to inactive on the seafloor, mimicking the end of venting while allowing for the exact time when venting ceased to be known, something not possible when sampling naturally formed inactive SMS. Microbial community diversity and metabolism will be analyzed in parallel with bulk and fine-scale geological measurements for active, transitioning, and inactive sulfides. This seafloor experimental and analytical approach will provide knowledge of how microbial communities, rates of biogeochemical transformations, and geological conditions change as SMS transition from hot and actively venting to cold and inactive. Students in grades 6-8 will be entrained into the project through research cruise "ship-to-shore" interactions and communications, post-cruise workshops for educators working with students typically underrepresented in STEM fields, and a collaboration with the Science, Engineering, Art and Design Gallery (SEAD), a community and economic development project in Bryan, TX. Hydrothermal vents are quantitatively important to the biology and chemistry of the deep ocean, but the vast majority of current knowledge focuses on actively venting deposits. However, after venting ceases, sulfides can persist on the seafloor for tens of thousands of years, making them long-lived, globally-abundant microbial substrates. In recent years, studies of inactive SMS found drastically different microbial communities than those on active deposits, indicating a succession of the microbial community, and thus a potentially different impact on deep ocean biodiversity and biogeochemistry than actively venting deposits. However, ages of the inactive structures are often not known, so it is impossible to estimate how quickly these changes occur, and how quickly co-occurring changes in sulfide mineralogy and microbiological communities occur. This project will provide the first insight into what happens at the microbial and mineralogical level as SMS initially transition from active to inactive. Active SMS will be sampled and analyzed for microbial community composition, functional capacity, gene expression and metabolic rates. Co-located subsamples will be analyzed for porosity and bulk and fine-scale mineralogy. Subsamples of those active SMS samples will be left on the seafloor to incubate and be collected weeks and a year or more later, with the same analyses conducted upon collection. This will allow for determination of microbiological and mineralogical changes that occur during that initial transition and for comparison with older inactive SMS from the same vent fields. Together, the data collected will be integrated to generate a conceptual model of succession of biology, mineralogy, porosity and pore distribution as vent deposits transition from active to inactive. This project will fill a knowledge gap about hydrothermal ecosystems and has the potential to transform the current understanding of diversity and rates of change in these important seafloor biomes.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.