Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, 35487, U.S.A.
Odum School of Ecology, University of Georgia, Athens, GA, 30602, U.S.A.
Biol Rev Camb Philos Soc. 2017 Nov;92(4):2003-2023. doi: 10.1111/brv.12318. Epub 2016 Dec 23.
The role of animals in modulating nutrient cycling [hereafter, consumer-driven nutrient dynamics (CND)] has been accepted as an important influence on both community structure and ecosystem function in aquatic systems. Yet there is great variability in the influence of CND across species and ecosystems, and the causes of this variation are not well understood. Here, we review and synthesize the mechanisms behind CND in fresh waters. We reviewed 131 articles on CND published between 1973 and 1 June 2015. The rate of new publications in CND has increased from 1.4 papers per year during 1973-2002 to 7.3 per year during 2003-2015. The majority of investigations are in North America with many concentrating on fish. More recent studies have focused on animal-mediated nutrient excretion rates relative to nutrient demand and indirect impacts (e.g. decomposition). We identified several mechanisms that influence CND across levels of biological organization. Factors affecting the stoichiometric plasticity of consumers, including body size, feeding history and ontogeny, play an important role in determining the impact of individual consumers on nutrient dynamics and underlie the stoichiometry of CND across time and space. The abiotic characteristics of an ecosystem affect the net impact of consumers on ecosystem processes by influencing consumer metabolic processes (e.g. consumption and excretion/egestion rates), non-CND supply of nutrients and ecosystem nutrient demand. Furthermore, the transformation and transport of elements by populations and communities of consumers also influences the flow of energy and nutrients across ecosystem boundaries. This review highlights that shifts in community composition or biomass of consumers and eco-evolutionary underpinnings can have strong effects on the functional role of consumers in ecosystem processes, yet these are relatively unexplored aspects of CND. Future research should evaluate the value of using species traits and abiotic conditions to predict and understand the effects of consumers on ecosystem-level nutrient dynamics across temporal and spatial scales. Moreover, new work in CND should strive to integrate knowledge from disparate fields of ecology and environmental science, such as physiology and ecosystem ecology, to develop a comprehensive and mechanistic understanding of the functional role of consumers. Comparative and experimental studies that develop testable hypotheses to challenge the current assumptions of CND, including consumer stoichiometric homeostasis, are needed to assess the significance of CND among species and across freshwater ecosystems.
动物在调节营养循环中的作用（以下简称消费者驱动的营养动态[CND]）已被认为是水生系统中群落结构和生态系统功能的重要影响因素。然而，CND 在物种和生态系统中的影响存在很大的可变性，其原因尚不清楚。在这里，我们回顾和综合了淡水 CND 的机制。我们回顾了 1973 年至 2015 年 6 月 1 日期间发表的 131 篇关于 CND 的文章。CND 的新出版物数量从 1973-2002 年的每年 1.4 篇增加到 2003-2015 年的每年 7.3 篇。大多数研究都集中在北美，许多研究都集中在鱼类上。最近的研究更侧重于动物介导的营养排泄率与营养需求和间接影响（如分解）的关系。我们确定了几个影响生物组织各级 CND 的机制。影响消费者化学计量可塑性的因素，包括体型、摄食历史和个体发育，在决定单个消费者对营养动态的影响方面起着重要作用，并为时间和空间上的 CND 提供了化学计量基础。生态系统的非生物特征通过影响消费者的代谢过程（如摄食和排泄/吐出率）、非 CND 养分供应和生态系统养分需求，来影响消费者对生态系统过程的净影响。此外，消费者种群和群落对元素的转化和运输也会影响生态系统边界的能量和养分流动。本综述强调，消费者群落组成或生物量的变化以及生态进化基础可能对消费者在生态系统过程中的功能作用产生强烈影响，但这些是 CND 相对未被探索的方面。未来的研究应该评估使用物种特征和非生物条件来预测和理解消费者对跨时空生态系统水平养分动态的影响的价值。此外，CND 的新工作应该努力整合生态学和环境科学等不同领域的知识，如生理学和生态系统生态学，以对消费者的功能作用有一个全面和机制化的理解。需要进行比较和实验研究，以发展可测试的假设来挑战当前 CND 的假设，包括消费者化学计量内稳态，以评估 CND 在物种间和淡水生态系统中的重要性。
