Animals play an important and sometimes overlooked role in nutrient cycling. The role of animals in nutrient cycling is spatially and temporally variable, but few studies have evaluated the long-term importance of animal-mediated nutrient cycling in meeting nutrient demand by primary producers. We quantified the proportion of phytoplankton nutrient (phosphorus, P) demand met by excretion by gizzard shad (Dorosoma cepedianum) in a eutrophic reservoir where this species dominates fish biomass. From 2000 to 2014, gizzard shad excretion supported a variable proportion of phytoplankton P demand, averaging 7–27% among years over the growing season (spring and summer). Temporal patterns emerged, as gizzard shad consistently supported a higher proportion of demand during summer (mean 31%) than spring (8%). In spring, the proportion of demand met from gizzard shad excretion was best predicted by gizzard shad population biomass, stream discharge, and temperature. In summer, this proportion was best predicted only by biomass of the young-of-year (YOY) gizzard shad. Thus, variation in YOY shad biomass significantly alters nutrient supply, and future studies should explore the long-term role of animal population dynamics in nutrient cycling. Our study shows that several years of data are needed to perform a critical evaluation of the importance of animals in meeting ecosystem nutrient demand.

中文翻译：

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鱼类的营养排泄在 15 年内支持了湖泊初级生产力的可变但显着比例

动物在营养循环中扮演着重要但有时被忽视的角色。动物在养分循环中的作用在空间和时间上是可变的，但很少有研究评估动物介导的养分循环在满足初级生产者养分需求方面的长期重要性。我们量化了鲥鱼（Dorosoma cepedianum）排泄所满足的浮游植物营养（磷，P）需求的比例) 在富营养化水库中，该物种在鱼类生物量中占主导地位。从 2000 年到 2014 年，鲥鱼排泄物支持浮游植物 P 需求的可变比例，在生长季节（春季和夏季）的年份中平均为 7-27%。出现了时间模式，因为鲥鱼在夏季（平均 31%）一直支持比春季（8%）更高的需求比例。在春季，鲥鱼种群生物量、河流流量和温度最能预测鲥鱼排泄满足的需求比例。在夏季，这一比例只能通过幼年 (YOY) 鲥鱼的生物量来最好地预测。因此，YOY 鲥鱼生物量的变化显着改变了养分供应，未来的研究应该探索动物种群动态在养分循环中的长期作用。