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

动物可以通过将食物资源转化为影响氮和磷等营养物质循环的废物，在淡水生态系统中发挥关键作用。以前的研究集中在动物的溶解废物(如氨和磷酸盐)的生态重要性，称为排泄物，因为这些废物营养丰富，很容易被植物和细菌利用。然而，动物也会产生大量的颗粒废物，称为粪便。例如，撕碎树叶的溪流无脊椎动物将植物垃圾转化为细小的颗粒粪便，随后可以被运往下游，分解，或被其他动物消耗。根据饮食和来源动物的不同，粪便的属性可能会有很大差异，这表明动物粪便在更大的生态系统功能中发挥着特定物种的作用。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和排泄物对养分循环的影响。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，从而造福社会。研究结果有助于指导人类活动的管理，这些活动导致淡水中动物物种分布和营养物质污染的变化。该项目将采用实验室实验和实地调查相结合的方法，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，喂养营养含量低或高的饲料，并收集它们的胚胎，以确定它们的大小和化学结合，以及在几个月的过程中测量微生物分解和养分淋溶、吸收和矿化的速度。对Ozark源头溪流的定期调查将量化现存大型无脊椎动物碳、氮和磷的总排泄量和排泄量，并将这些动物通量与背景储量和溶解营养物质(如排泄物)和细颗粒有机物(如排泄物)的通量(如排泄物)进行比较。所有研究结果将被综合起来，用于模拟背景营养物浓度、动物群落组成以及溶解和颗粒元素的背景存量和通量的变化如何影响动物在河流生态系统中的作用。

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.