Fitting Mixotrophy into the Microbial Loop Paradigm: Advantages and Consequences of Mixotrophic Behavior Among Phagotrophic Algae

Caron混合营养是异养和光养营养在单一生物中的结合。在单细胞微藻中，各种各样的物种摄取颗粒有机物质。在混合营养行为中存在几种可能的适应性优势。到目前为止，吞噬行为提供了三种一般策略：(1)主要phagotrophic增长细菌丰度高,与光养作为机制非常缓慢的碎屑岩当细菌丰度较低,(2)主要与吞噬光养增长作为补充增长机制在低光强度,和(3)主要与吞噬光养增长作为一种机制来获取氮或磷等主要营养物质。本研究将重点研究吞噬性微藻与纯光养原生生物（藻类）和纯异养原生生物（原生动物）竞争的能力。该框架包括一个将混合营养纳入简单微生物食物网的模型，以产生关于吞噬藻类与非吞噬藻类和原生动物竞争能力的假设。该模型是基于对混合营养行为的三种策略的理解。假设将在实验室中通过连续培养中藻类、原生动物和吞噬藻类之间的一系列竞争实验进行测试。实验将考察光照限制、不稳定溶解有机碳的添加和无机营养限制对吞噬藻类与非吞噬藻类和原生动物竞争生长的影响。指导假设是，不同种类的吞噬藻类表现出的不同行为为它们提供了竞争优势，这将导致它们在特定环境下的成功。这些实验将建立这些环境，并为解释自然界中混合营养物种的分布提供有价值的见解。

9508571 Caron Mixotrophy is the combination of heterotrophic and phototrophic nutrition in a single organism. Among the unicellular microalgae, a wide variety of species ingest particulate organic material. Several possible adaptive advantages exist for mixotrophic behavior among phagotrophic algae. Thus far, three general strategies are served by phagotrophic behavior: (1) primarily phagotrophic growth at high bacterial abundances, with phototrophy serving as a mechanism for very slow grouth when bacteria are present at low abundances, (2) primarily phototrophic growth with phagotrophy serving as a mechanism for supplementing growth at low light intensities, and (3) primarily phototrophic growth with phagotrophy serving as a mechanism for acquiring major nutrients such as nitrogen or phosphorus. This research will focus on the ability of phagotrophic microalgae to compete with purely phototrophic protists (algae) and purely heterotrophic protists (protozoa). The framework includes a model that incorporates mixotrophy into a simple microbial food web in order to generate hypotheses concerning the ability of phagotrophic algae to compete with nonphagotrophic algae and protozoa. The model is based on the understanding of the three strategies for mixotrophic behavior. Hypotheses will be tested in the laboratory via a series of competition experiments between algae, protozoa, and phagotrophic algae in continuous cultures. Experiments will examine the effects of light limitation, additions of labile dissolved organic carbon, and inorganic nutrient limitation on the growth of phagotrophic algae competing with nonphagotrophic algae and protozoa. The guiding hypothesis is that the different behaviors exhibited by different species of phagotrophic algae provide them with a competitive advantage that will result in their success under particular circumstances. These experiments will establish those circumstances and provide valuable insights for explaining the distribution of mixotrophic species in na ture.