Weisse Thomas
Research Department for Limnology, University of Innsbruck, Mondsee, Austria.
Front Microbiol. 2025 Jun 10;16:1559802. doi: 10.3389/fmicb.2025.1559802. eCollection 2025.
Protists are paramount for biogeochemical cycling in every aquatic ecosystem due to their vast population sizes and physiological versatility. Numerical response (NR) and functional response (FR) experiments are cornerstones of trait-based functional ecology and are increasingly studied experimentally with phagotrophic aquatic protists. Such experiments provide estimates of protist growth, production and consumption rates in relation to biotic (food supply) and abiotic variables (e.g., temperature, pH, and salinity) that can be used in mathematical models of ecosystem dynamics. Until now, NR and FR experiments lack standardization and are subject to potential pitfalls that received little attention in the literature. It is a common misconception that an experimental investigation of a phagotrophic protist's growth and ingestion rates represents a single experiment with replication. I demonstrate that a typical NR or FR experiment consists of a series of individual experiments in which not only the experimental target variable (food, i.e., prey abundance or biomass) changes but also other factors (physiological conditions of prey and predator, nutrient levels, unwanted contaminants) vary that may affect the experimental outcome. Standardizing all variables affecting a series of NR and FR experiments is virtually impossible. I further explain why FR experiments are more prone to experimental bias than NR experiments. Since it is principally impossible to perform an "ideal" NR or FR experiment, fulfilling all criteria of experimental standardization, the goal is to reduce the "noise" to obtain statistically significant and reproducible results. To this end, I provide guidelines that may help achieve this goal in future studies.
由于原生生物数量众多且生理功能多样，它们在每个水生生态系统的生物地球化学循环中都至关重要。数值反应（NR）和功能反应（FR）实验是基于性状的功能生态学的基石，并且越来越多地通过吞噬性水生原生生物进行实验研究。此类实验提供了与生物（食物供应）和非生物变量（例如温度、pH值和盐度）相关的原生生物生长、生产和消耗率的估计值，这些估计值可用于生态系统动态的数学模型。到目前为止，NR和FR实验缺乏标准化，并且存在一些潜在的陷阱，而这些陷阱在文献中很少受到关注。一个常见的误解是，对吞噬性原生生物的生长和摄食率进行实验研究代表了一个具有重复的单一实验。我证明，一个典型的NR或FR实验由一系列单独的实验组成，其中不仅实验目标变量（食物，即猎物丰度或生物量）会发生变化，而且其他因素（猎物和捕食者的生理条件、营养水平、有害污染物）也会有所不同，这些因素可能会影响实验结果。对影响一系列NR和FR实验的所有变量进行标准化几乎是不可能的。我进一步解释了为什么FR实验比NR实验更容易出现实验偏差。由于原则上不可能进行一个满足所有实验标准化标准的“理想”NR或FR实验，因此目标是减少“噪声”以获得具有统计显著性和可重复性的结果。为此，我提供了一些指导方针，可能有助于在未来的研究中实现这一目标。
