Collaborative Research: Understanding the distribution and biogeochemical role of anaerobic microenvironments in the ocean

直到最近，人们还认为有机物分解（呼吸作用）主要发生在含氧海水中；然而，有证据表明，呼吸作用可以在低氧条件下（厌氧）发生，类似于在悬浮颗粒微环境中发现的情况。因此，存在这种可能性，即这些厌氧反应比以前认为的更广泛，并可能在硫、氮和一些微量金属的循环中发挥重要作用。来自加州大学洛杉矶分校和华盛顿大学的研究人员计划通过开发粒子氧化还原模型来研究这些反应，以模拟厌氧微环境的生物地球化学，并做出预测，这些预测可以根据现有的海洋数据进行测试（GEOTRACES程序）。该研究旨在了解这些颗粒微环境中氮和硫循环所需的条件，硫化物沉淀过程中微量金属的清除，并开发颗粒结合反硝化（微生物去除氮）的示踪剂。该项目将首次资助两位终身教授，他们致力于教育和公众宣传，以帮助扩大海洋科学的参与。其中一名调查人员将作为青年教育工作者参与“冰上学生”项目，该项目举办研讨会，让年轻人获得在海上学习海洋学的经验，而另一名调查人员将组织一系列研讨会，让罗切斯特市学区的学生参与科学研究。该项目旨在调查近年来出现的证据，即有机颗粒内的厌氧微环境在整个海洋中广泛存在，并且在其他含氧水域中对反硝化和硫还原率有重要贡献。为此，研究人员计划开发一种新的建模框架来模拟厌氧微环境的生物地球化学，并做出预测，这些预测可以根据GEOTRACES程序等现有观察结果进行测试。总体而言，本研究的目标是：(1)了解导致这些厌氧微环境的水柱条件和颗粒性质；(2)测试硫酸盐还原速率是否与已知的低氧水的金属沉淀特征一致；(3)预测颗粒结合反硝化的地球化学特征，并从氮示踪剂的大规模分布中确定其速率。了解在水柱中有机颗粒厌氧微环境中发生的厌氧过程可能会更新氮、硫和微量金属的生物地球化学循环。

Until recently, organic matter decomposition (respiration) was thought to occur primarily in oxygenated seawater; however, evidence has surfaced that respiration can occur under low oxygen conditions (anaerobic) similar to those found within microenvironments of suspended particles. As such, the possibility exists that these anaerobic reactions are more widespread than previously thought and could play a significant role in the cycling of sulfur, nitrogen, and some trace metals. Researchers from the University of California-Los Angeles and the University of Washington plan to study these reactions by developing a particle-redox model to simulate the biogeochemistry of anaerobic microenvironments and make predictions which can be tested against available ocean data (GEOTRACES program). The study is intended to understand the conditions needed to cycle nitrogen and sulfur in these particle microenvironments, the scavenging of trace metals during sulfide precipitations, and develop a tracer for particle bound denitrification (removal of nitrogen by microbes). This project will be the first funding support for two tenure-track faculty who are dedicated to education and public outreach to help broaden involvement in ocean sciences. One of the investigators will be involved as a youth educator in the "Students on Ice" program which conducts workshops that allows youth to gain experience at sea learning about oceanography, whereas the other would organize a series of workshops to engage students from the Rochester City School District in science.This project seeks to investigate the evidence that has been coming out in recent years that anaerobic microenvironments within organic particles are widespread throughout the ocean and are a significant contributor to denitrification and sulfur reduction rates in otherwise oxygenated waters. To do so, the researchers plan to develop a new modeling framework to simulate the biogeochemistry of anaerobic microenvironments and make predictions which can be tested against available observations such as those from the GEOTRACES program. Overall the objectives of this research are to (1) understand the water column conditions and particle properties that lead to these anaerobic microenvironments, (2) test whether sulfate reduction rates are consistent with the metal precipitation signatures known for low oxygen water, and (3) predict the geochemical signature of particle bound denitrification and determine its rate from the large-scale distribution of nitrogen tracers. Understanding the anaerobic processes taking place within anaerobic microenvironments of organic particles in the water column is likely to update the biogeochemical cycles of nitrogen, sulfur, and trace metals.