CAREER: Understanding heterogeneity in lake biogeochemistry across time and space

淡水水生生态系统包括湖泊、池塘和水库，为社会提供重要服务，包括发电、娱乐机会和提供清洁饮用水。此外，淡水水生生态系统是全球碳循环的主要组成部分。湖泊向大气中排放了大量二氧化碳，这是由内部有机物分解和来自周围流域的外部无机碳输入的共同作用产生的。在世界各地的湖泊中，随着有机体分解有机物而消耗的溶解氧正在减少，威胁到这些生态系统支持其所在生物目前的多样性和生物量的能力。过去试图了解湖泊中二氧化碳和溶解氧耦合动力学的尝试并没有考虑到光照强度和温度或水柱的非均质性的季节性变化，这两者都影响着两种气体的总通量。该项目旨在了解环境条件在时间和空间上的异质性如何影响水生生态系统中的碳和氧平衡，从而提高我们对湖泊在全球碳循环中所起作用的理解。总之，该项目的综合研究和教育计划将通过改进课程材料、举办大型讲习班和在当地开展外联活动，为广泛的学生和早期职业科学家提供教育和培训机会。该项目还将利用许多组织和机构现有的数据集，通过汇编和协调不同数据集的过程获得的见解将可用于许多其他网络和研究工作。最后，与世界各地的公民科学家和湖泊协会的接触将利用比较网络科学的力量来了解全球范围内的各个湖泊的情况。湖泊往往表现出实质性和动态的结构异质性，这主要是由热层化推动的。该项目的重点是二氧化碳和溶解氧在湖泊中的产生和消耗，以及时间和空间上的异质性如何调节这些关键生物地球化学通量的动态。湖泊是全球重要的碳循环热点，向大气排放的二氧化碳大约与世界海洋吸收的二氧化碳一样多。理论上，二氧化碳和溶解氧通过代谢过程以化学计量方式耦合，但在水生生态系统中，经常发生偏离基于化学计量和大气分压的预期的情况。了解是什么导致了这些偏离，可能会提供对湖泊潜在的生物地球化学过程的洞察，并可能使更准确地预测湖泊的大陆尺度二氧化碳排放。该项目旨在结合高频传感器观测、手动收集的数据、长期数据集和生态系统建模，以了解大环境梯度上湖泊二氧化碳和溶解氧的动态。数据将从不同的来源获得和协调，如国家生态观测网络(NEON)和全球湖泊生态观测网络(GLEON)中的合作科学家和组织。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Freshwater aquatic ecosystems, which include lakes, ponds, and reservoirs, provide important services to society, including power generation, recreational opportunities, and the provisioning of clean drinking water. Additionally, freshwater aquatic ecosystems are a major component of the global carbon cycle. Lakes emit a substantial amount of carbon dioxide to the atmosphere, which is derived from a combination of internal organic matter breakdown and external inputs of inorganic carbon from surrounding watersheds. Dissolved oxygen, which is consumed as organisms break down organic matter, is declining in lakes around the world, threatening the ability of these ecosystems to support the current diversity and biomass of organisms they harbor. Past attempts to understand coupled carbon dioxide and dissolved oxygen dynamics in lakes have not accounted for seasonal variation in light intensity and temperature or water column heterogeneity, both of which influence gross fluxes of both gasses. This project seeks to understand how heterogeneity in environmental conditions, in both time and space, impacts carbon and oxygen balance in aquatic ecosystems, and thus improve our understanding of the role lakes play in the global carbon cycle. Together, the integrated research and education plan of this project will provide educational and training opportunities to a wide range of students and early career scientists through improved course materials, a large workshop, and local outreach efforts. This project will also leverage datasets that exist at many organizations and institutions, and the insights gained via the process of compiling and harmonizing diverse data sets will be translatable to many other networks and research efforts. Finally, outreach to citizen-scientists and lake associations around the world will leverage the power of comparative network science to understand individual lake conditions in a global context.Lakes often exhibit substantial and dynamic structural heterogeneity, largely driven by thermal stratification. This project focuses on the production and consumption of carbon dioxide and dissolved oxygen in lakes, and how heterogeneity in time and space regulate the dynamics of these critical biogeochemical fluxes. Lakes are globally important hot-spots of carbon cycling, venting about as much carbon dioxide to the atmosphere as is taken up by the world’s oceans. Theoretically, carbon dioxide and dissolved oxygen are stoichiometrically coupled via metabolic processes, but departures from expectations based on stoichiometry and partial pressure in the atmosphere regularly occur in aquatic ecosystems. Understanding what causes these departures may provide insights into underlying biogeochemical processing in lakes, and may enable more accurate predictions of continental-scale carbon dioxide emissions from lakes. This project aims to combine high-frequency sensor observations, manually collected data, long-term data sets and ecosystem modeling to understand the dynamics of lake carbon dioxide and dissolved oxygen across large environmental gradients. Data will be obtained and harmonized from diverse sources such as the National Ecological Observatory Network (NEON) and collaborating scientists and organizations in the Global Lake Ecological Observatory Network (GLEON).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.