Collaborative Research: Are Low-Temperature Hydrothermal Vents an Important but Overlooked Source of Stabilized Dissolved Iron to the Ocean?

合作研究：低温热液喷口是否是海洋稳定溶解铁的重要但被忽视的来源？

• 批准号: 1755571
• 负责人: Chris German
• 金额: $ 15.27万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-04-01 至 2022-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1755571&HistoricalAwards=false
• 关键词: Collaborative; Research; Low; Temperature; Hydrothermal

Hydrothermal vents are hot springs on the seafloor. They are often thousands of meters below the surface of the ocean along the large volcanic mountain ranges called the mid-ocean ridges. Relatively little is known about these hydrothermal vents because they exist so far from the ocean surface. Instead of lava, these vents emit warm to hot fluids (from several ºC up to 350 ºC) into the ocean, and contain high concentrations of a wide range of dissolved chemicals. One of these chemicals, iron, has been studied extensively by ocean scientists because of its importance as an essential nutrient for the microscopic photosynthetic algae called phytoplankton that grow in surface ocean waters. Scientists once thought that most of the dissolved iron coming out of hydrothermal vent fluids would quickly precipitate (form a solid and sink) near the vents, as a result of chemical reactions between the hot vent fluid and cold seawater, and therefore only small amounts of dissolved iron could be transported from the deep sea mid-ocean ridges to surface waters where phytoplankton grow. However, on a recent scientific expedition over one of the most active mid-ocean ridges called the southern East Pacific Rise (SEPR), scientists discovered that much of the dissolved iron discharged from the SEPR hydrothermal vents was in fact transported thousands of kilometers across the deep ocean. In addition, computer simulations suggest that a substantial amount of this ?hydrothermal iron? is transported as far as the surface waters of the Southern Ocean around Antarctica, where it could support the growth of phytoplankton.Scientists from the University of Washington, Woods Hole Oceanographic Institution and Old Dominion University will return to the SEPR aboard a research ship and make additional measurements to better understand how hydrothermal vents add dissolved iron to the deep ocean. They will use specialized sampling equipment, including unmanned miniature submarines called autonomous underwater vehicles (AUVs), to map the distribution of hydrothermal vents in this region, and collect water samples from both high temperature (250-350 ºC) and low temperature ( 150 ºC) vents. These samples will be analyzed for chemicals that are enriched in the hydrothermal vent fluids, such as iron, manganese and helium-3, which will provide information on the chemical changes that occur as the hydrothermal vent fluids mix with surrounding seawater and are carried away from the SEPR. The scientists will use their observations and chemical analyses to address the following major questions: 1) are there more hydrothermal vents along mid ocean ridges than previously thought? and (2) are low temperature hydrothermal vents especially favorable for stabilizing dissolved iron, and ultimately transporting it to the surface ocean where it supports phytoplankton growth? The project will contribute to the education and training of a graduate student and two senior undergraduate students, and outcomes will be incorporated into high school STEM curricula. The research activities will be communicated via public lectures and media releases, and project results will be disseminated to the scientific community by conference presentations, publications in peer-reviewed scientific journals, and freely available on-line archived data.Along thousands of kilometers of the seafloor volcanic chains known as the mid-ocean ridges, hydrothermal vents discharge hot, acidic, metal-rich fluids into the deep ocean. These submarine hot springs are a major gateway for the exchange of heat and chemicals between the solid earth and the deep ocean, and have received intensive scientific study during the last 40 years. This research has overwhelmingly focused on high temperature (~200-350°C) hydrothermal vents. Lower temperature (150°C) hydrothermal venting has received relatively little attention, although results from recent observational and modeling studies point to the greater abundance of low temperature discharge along the mid-ocean ridges, and its potential importance for the input of elements and chemical compounds into the deep ocean. Among the elements that are enriched in hydrothermal vent fluids, iron has received attention because of its role as an essential nutrient for primary production in the surface ocean. It has long been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to mid-ocean ridge sources, and thus of limited importance for ocean chemistry. But this view has been challenged by recent studies which suggest that chemical stabilization of hydrothermal dissolved iron may facilitate its long-range transport in the deep ocean. In particular, results from the US GEOTRACES program have revealed the lateral transport of a plume of hydrothermal dissolved iron over several thousand kilometers westward from its source region on the southern East Pacific Rise (SEPR).In this project, investigators from the University of Washington, Woods Hole Oceanographic Institution and Old Dominion University will carry out a field research program on the SEPR to test the overarching hypothesis that diffuse low-temperature hydrothermal venting is a major a source of chemically-stabilized dissolved iron to the deep ocean, and hence plays an important but previously overlooked role in the ocean iron cycle. The ship-based field program will use an autonomous underwater vehicle equipped with in-situ optical and chemical sensors to identify plumes of both diffuse (low-temperature) and discrete (high-temperature) hydrothermal discharge along the SEPR. Emissions from multiple sites of both low and high temperature hydrothermal venting will be sampled for shipboard and post-cruise analyses of iron and other trace metals, and the inert hydrothermal "tracer" helium-3. The resulting data will be used to test two specific hypotheses: (1) the population of active hydrothermal discharge sites along mid ocean ridges is greater than previously estimated, (2) low temperature hydrothermal venting is conducive to the chemical stabilization of dissolved iron, thus facilitating its export to the ocean interior and ultimately to surface ocean where it supports primary production by phytoplankton. The information obtained in this research will facilitate inclusion of iron and other trace elements in numerical models of ocean biology and biogeochemistry, which will improve the ability to predict how the ocean will respond to and modulate future climatic and environmental changes.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.

水热通风孔是海底温泉。它们通常沿着大型火山山脉山脉在海洋表面以下数千米，称为中山山脊。对于这些热液通风孔的了解很少，因为它们离海面很远。这些通风孔代替熔岩，将温暖到热流体（从几ºC到350ºC）进入海洋，并含有高浓度的各种溶解化学物质。海洋科学家对这些化学物质之一进行了广泛的研究，因为它是在地表海水中生长的称为浮游植物的微观光合藻类的重要营养素。科学家曾经认为，由于热通风液和冷海水之间的化学反应，大多数从热液通风液中产生的溶解的铁会迅速在通风孔附近迅速沉淀（形成固体和水槽），因此只能从深海中海中的中层海洋中的含水层转运到植物群生长的深海中层中的中层中的中间海中。然而，在最近的一次科学探险中，对最活跃的中山山脊之一，称为南太平洋南部崛起（SEPR），科学家发现，从SEPR水热通风孔排出的许多溶解的铁实际上是在深海中运输了数千公里。此外，计算机模拟表明其中大量的水热铁？被运输到南极周围南大洋的地面水，在那里可以支持浮游植物的生长。华盛顿大学，伍兹霍尔海洋学机构和旧多米尼奥大学的成员将返回一艘研究船的SEPR，并进行更多的测量，以更好地了解水热溶解的水面为深海溶解的铁。他们将使用专门的采样设备，包括称为自动水下车辆（AUV）的无人微型潜艇，以绘制该地区的热液通风孔的分布，并从高温（250-350ºC）和低温（150ºC）的通风口收集水样。将分析这些样品的化学物质，这些化学物质富含水热烟道（例如铁，锰和氦3），这些化学物质将提供有关当水热笛子与周围海水混合并从SEPR携带的化学变化的信息。科学家将使用他们的观察结果和化学分析来解决以下主要问题：1）沿海脊中的水热通风孔比以前想象的要多？ （2）是低温水热通风孔，特别有利于稳定溶解的铁，并最终将其运输到地面海洋。它在哪里支持浮游植物的增长？该项目将有助于研究生和两名高级本科生的教育和培训，结果将纳入高中STEM课程中。研究活动将通过公开讲座和媒体发行来传达，项目结果将通过会议演讲，同行评审的科学期刊的出版物传播给科学界，并免费提供的在线存档数据。数千公里的海藻火山链中的中层山脉被众所周知，将其用于中等轨道，将其置于中等范围内，将其置于水平较深的水平上，富于富有酸性的酸性。这些海底温泉是在固体地球和深海之间交换热量和化学物质的主要门户，并且在过去40年中接受了深入的科学研究。这项研究压倒性地集中在高温（〜200-350°C）较低温度（150°C）的水热通风孔中，尽管最近的观察和建模研究的结果表明，低温排放量更大，沿元素中期山脊及其对元素的潜在元素和化学元素的潜在重要性。在富含水热烟道的元素中，铁被关注是因为它是表面海洋初级生产的重要营养素的作用。长期以来，人们一直认为，大多数溶解的铁被水热通风孔排出，从接近海洋山脊源的溶液中丢失，因此对海洋化学的重要性有限。但是，最近的研究挑战了这种观点，该研究表明，水热溶解铁的化学稳定可能有助于其在深海中的远距离运输。特别是，美国地理位置计划的结果揭示了从其在东部太平洋南部南部的源地区以西数千公里（SEPR）向西数千公里的水热溶解铁的横向运输（SEPR）。在这个项目中，华盛顿大学的调查人员，伍德斯大学孔孔海洋学机构和旧多米尼奥大学将在跨层次的研究中进行现场研究，以跨越iSPR的现场研究。化学稳定的溶解铁向深海的主要来源，因此在海洋铁循环中起着重要但以前被忽视的作用。基于船舶的现场计划将使用配备现场光学传感器的自动驾驶水下车辆，以识别沿SEPR沿SEPR的弥漫性（低温）和离散（高温）热液排放的羽毛。低温和高温热液通风口的多个位点的排放将进行采样，以进行铁板和铁和其他痕量金属的杂货后分析，以及惰性热液“示踪剂”氦氦-3。 The resulting data will be used to test two specific hypotheses: (1) the population of active hydrothermal discharge sites along mid ocean ridges is greater than previously estimated, (2) low temperature hydrothermal venting is conducting to the chemical stabilization of dissolved iron, This award reflects NSF's statutory mission and has been deemed fatty of iron and other trace elements in numerical models of ocean biology and biogeochemistry, which will improve the ability to预测海洋将如何应对并调节未来的杂物和环境变化。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响审查标准来评估值得支持的。

项目成果

Abundance of low-temperature axial venting at the equatorial East Pacific Rise

• DOI: 10.1016/j.dsr.2020.103426
• 发表时间: 2020-01-01
• 期刊: Deep Sea Res. Part I: Oceanogr. Res. Pap
• 作者: Chen, Sheng;Tao, Chunhui;German, Christopher R.
• 通讯作者: German, Christopher R.