Collaborative Research: Algal photosynthetic priming and photolysis as stimulators of ecosystem-level detrital processing by microbial heterotrophs

淡水湿地提供许多有价值的生态系统服务，包括为野生动物提供食物和栖息地，改善水质，防洪和保护湖泊海岸线免受侵蚀。这些特性使湿地成为我国重要的环境、娱乐和经济资源。在淡水湿地中，从水中长出的高大植物，如香茅，往往占产生的植物物质的很大一部分。这些植物表现出多产的生长速度，并吸收了大量的营养污染物，在此过程中改善了水质。这些植物物质中的大部分并不直接被动物消耗，而是死亡，并被微生物(细菌和真菌)分解。在分解过程中，被困在植物组织中的营养物质可能通过细菌和真菌分解者的活动而释放。生长在腐烂植物上的细菌和真菌也是许多无脊椎动物的关键食物来源，并在湿地栖息地的食物链(例如鱼类和水禽)上形成能量和营养流动的纽带。因此，新兴植物的生产力、养分吸收和分解将对湿地功能的几乎所有方面产生深远影响。这项研究项目将测量细菌和真菌在湿地植物腐烂中的重要性，并调查它们与藻类的潜在相互作用如何影响植物物质分解和养分循环的速度。微生物是地球上营养物质循环的关键参与者。这种循环，通常被称为生物地球化学循环，包括所有涉及的生物、地质和化学因素。了解微生物生态学对于我们应对人类社会面临的重大挑战至关重要，这些挑战包括自然生态系统的保护和管理以及减缓气候变化。除了培养博士后学者外，这项研究还将通过协作、多方面的努力培训本科生和研究生，以了解关键的生态系统过程--分解。通过这些努力，研究人员还将参与一系列现有的大学项目和协调的外展活动，旨在招募代表性不足的群体进入科学领域，并加强小学到大学层面的科学教育。该项目的总体目标是了解藻类、细菌和真菌在分解植物凋落物过程中代谢相互作用的性质，并量化这些相互作用如何影响湿地中植物凋落物的分解和碳循环。溶解态和颗粒态有机物的光解是水生生态系统中一种重要的非生物分解过程。相比之下，通过藻类刺激凋落物相关的异养微生物来促进分解直到最近才被考虑。该团队之前的研究已经证明了异养微生物对自然腐烂的植物凋落物中藻类光合作用的快速代谢反应，从而确定了藻类“引发效应”对微生物介导的凋落物分解的潜在作用，然而，藻类引发和光解在促进水生生态系统中凋落物分解方面的相对重要性尚不清楚。本项目将涉及一系列沼泽生态系统的野外和实验室实验，研究凋落物分解的光刺激作用的三个关键问题：1)藻类光合作用启动和光解作用在促进微生物介导的有机物分解方面的相对重要性是什么？2)光解作用和自养-异养生物相互作用对生态系统尺度碳循环的影响是什么？3)在腐烂的植物凋落物中，调节自养-异养生物相互作用的机制是什么？

Freshwater wetlands provide many valuable ecosystem services, including the provision of food and habitat for wildlife, improvement of water quality, flood protection, and defense of lake shorelines from erosion. These attributes make wetlands a significant environmental, recreational, and economic resource for our nation. In freshwater wetlands, tall plants emerging from the water, such as cattails, often account for a large fraction of the plant matter produced. These plants exhibit prolific rates of growth and absorb large amounts of nutrient contaminants, improving water quality in the process. Most of this plant matter is not directly consumed by animals, but instead dies and is decomposed by microorganisms (bacteria and fungi). During decomposition, nutrients trapped within plant tissues may be released via the activity of bacterial and fungal decomposers. Bacteria and fungi growing on decaying plants also serve as a key food resource for many invertebrate animals, and form a link in the flow of energy and nutrients up the food chain (to fish and waterfowl, for example) in wetland habitats. As a consequence, the productivity, nutrient uptake, and decomposition of emergent plants will profoundly affect nearly all aspects of wetland function. This research project will measure the importance of bacteria and fungi in wetland plant decay, and investigate how their potential interactions with algae affect rates of plant matter decomposition and nutrient cycling. Microorganisms are key players in the circulation of nutrients on Earth. This circulation, often referred to as biogeochemical cycling, includes all of the biological, geological and chemical factors that are involved. Understanding the ecology of microorganisms is essential for us to meet the major challenges facing human society, such as conservation and management of natural ecosystems and mitigation of climate change. In addition to training a postdoctoral scholar, this research will train undergraduate and graduate students through a collaborative, multifaceted effort to understand a key ecosystem process, decomposition. Through these efforts researchers will also participate in a series of existing university programs and coordinated outreach activities aimed at recruiting underrepresented groups into the sciences and strengthening science education at the elementary through university levels.The overarching goal of this project is to understand the nature of metabolic interactions among algae, bacteria, and fungi in decomposing plant litter, and to quantify how these interactions influence plant litter decomposition and carbon cycling in wetlands. Photolysis of dissolved and particulate organic matter is widely accepted as an important abiotic decomposition process in aquatic ecosystems. In contrast, enhanced decomposition via algal stimulation of litter-associated heterotrophic microbes has only recently been considered. Prior research by this team has documented rapid metabolic responses of heterotrophic microbes to algal photosynthesis in natural decaying plant litter, thus establishing the potential for algal "priming effects" on microbial-mediated litter decomposition, yet, the relative importance of algal priming and photolysis in facilitating litter decomposition in aquatic ecosystems remains unknown. This project will involve a series of field and laboratory experiments in marsh ecosystems, investigating three key questions centered on photostimulation of litter decomposition: 1) What is the relative importance of algal photosynthetic priming vs. photolysis in facilitating microbial-mediated organic matter decomposition? 2) What is the influence of photolysis and autotroph-heterotroph interactions on ecosystem-scale carbon cycling" 3) What are the mechanisms mediating autotroph-heterotroph interactions in decaying plant litter?