Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Santa Cruz, CA, 95060, USA.
Cawthron Institute, Nelson, New Zealand.
Ecol Lett. 2020 Aug;23(8):1287-1297. doi: 10.1111/ele.13532. Epub 2020 May 31.
Experiments have revealed much about top-down and bottom-up control in ecosystems, but manipulative experiments are limited in spatial and temporal scale. To obtain a more nuanced understanding of trophic control over large scales, we explored long-term time-series data from 13 globally distributed lakes and used empirical dynamic modelling to quantify interaction strengths between zooplankton and phytoplankton over time within and across lakes. Across all lakes, top-down effects were associated with nutrients, switching from negative in mesotrophic lakes to positive in oligotrophic lakes. This result suggests that zooplankton nutrient recycling exceeds grazing pressure in nutrient-limited systems. Within individual lakes, results were consistent with a 'seasonal reset' hypothesis in which top-down and bottom-up interactions varied seasonally and were both strongest at the beginning of the growing season. Thus, trophic control is not static, but varies with abiotic conditions - dynamics that only become evident when observing changes over large spatial and temporal scales.
实验已经揭示了生态系统中自上而下和自下而上控制的很多方面，但操纵性实验在空间和时间尺度上受到限制。为了更细致地了解营养级控制在大尺度上的情况，我们探索了来自 13 个全球分布湖泊的长期时间序列数据，并使用经验动态建模来量化湖泊内和湖泊间浮游动物和浮游植物之间的相互作用强度随时间的变化。在所有湖泊中，顶级捕食者的作用与营养物质有关，在中营养湖泊中呈负相关，在贫营养湖泊中呈正相关。这一结果表明，在营养有限的系统中，浮游动物的营养循环超过了摄食压力。在单个湖泊中，结果与“季节性重置”假说一致，即自上而下和自下而上的相互作用随季节而变化，并且在生长季节开始时最强。因此，营养级控制不是静态的，而是随非生物条件而变化——只有在观察大空间和时间尺度的变化时，这些动态才会变得明显。
