NSF Award
1456978
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.<br/><br/>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?
