DISSERTATION RESEARCH: Assessing controls, fates, and significance of animal egesta in stream ecosystems

动物可以在淡水生态系统中发挥关键作用，将食物资源转化为影响氮和磷等营养物质循环的废物。以前的研究集中在动物的溶解废物（例如铵和磷酸盐）的生态重要性，称为排泄物，因为这些废物营养丰富，易于被植物和细菌生物利用。然而，动物也产生大量的颗粒废物，称为粪便。例如，树叶粉碎流无脊椎动物将植物垃圾转化为细颗粒粪便，随后可以被下游运输，分解或被其他动物消耗。粪便的属性可能因饮食和来源动物而异，这表明动物粪便在生态系统的更大功能中具有物种特异性作用。在这个项目中，研究人员将探索影响动物粪便属性的因素，并比较粪便对河流生态系统中养分循环的影响。该项目将通过提供有关动物在生态系统中的重要性的新信息，并为多名本科生和一名研究生提供职业发展来造福社会。研究结果可以帮助指导人类活动的管理，推动动物物种分布和淡水营养盐污染的变化。本项目将采用实验室实验和实地调查相结合的方法来评估河流生态系统中动物排泄物（粪便）的控制，命运和意义。来自多个物种的主要放牧和切碎的大型无脊椎动物将被带到实验室，喂食低或高营养含量的饮食，并收集其排泄物，以表征大小和化学结合力，以及测量微生物分解率和养分浸出，吸收和矿化在几个月的过程中。经常性调查的Ozark源头流将量化总排泄和排泄的碳，氮，磷的现存大型无脊椎动物和比较这些动物通量的背景股票和通量的溶解营养物质（在排泄物的情况下）和细颗粒有机物（在情况下的egesta）。所有的研究结果将被合成的背景养分浓度，动物群落组成，背景股票和溶解和颗粒元素通量的变化如何影响流生态系统中的动物的角色建模。

Animals can play key roles in freshwater ecosystems by converting food resources into waste products that affect the cycling of nutrients such as nitrogen and phosphorus. Previous research has focused on the ecological importance of dissolved wastes (e.g. ammonium and phosphate) from animals, termed excreta, because these wastes are nutrient-rich and readily bioavailable to plants and bacteria. However, animals also produce substantial amounts of particulate wastes, termed feces. For example, leaf-shredding stream invertebrates convert plant litter into fine particulate feces that can be subsequently transported downstream, broken down, or consumed by other animals. Feces may vary widely in attributes depending on diet and the source animal, suggesting species-specific roles of animal feces in larger functioning of ecosystems. In this project, researchers will explore factors influencing attributes of animal feces and compare the impact of feces on nutrient cycling to that of excreta in stream ecosystems. This project will benefit society by contributing novel information about the importance of animals in ecosystems and providing career development for multiple undergraduates and one graduate student. Results can help guide management of human activities that drive changes in animal species distribution and nutrient pollution in freshwaters.This project will employ a combination of laboratory experiments and field surveys to assess controls, fates, and the significance of animal egesta (feces) in stream ecosystems. Dominant grazing and shredding macroinvertebrates from multiple species will be brought to the laboratory, fed diets of low or high nutrient content, and their egesta collected to characterize size and chemical binding as well as measure rates of microbial decomposition and nutrient leaching, uptake, and mineralization over the course of several months. Recurrent surveys of an Ozark headwater stream will quantify total excretion and egestion of carbon, nitrogen, and phosphorus by extant macroinvertebrates and compare these animal fluxes to background stocks and fluxes of dissolved nutrients (in the case of excreta) and fine particulate organic matter (in the case of egesta). All findings will be synthesized for modeling of how variation in background nutrient concentrations, animal community composition, and background stocks and fluxes of dissolved and particulate elements can affect the roles of animals in stream ecosystems.