Light-aided digestion of Phytoplankton Prey by Heterotrophic Protist Grazers

光与营养供应一起，是构成海洋生命的主要非生物资源。除了趋光性和生物发光等各种行为现象外，光还没有被认为直接影响海洋浮游动物的能量学。在最近的研究中，我们发现了三种异养(非光合作用)原生生物直接利用光能消化浮游植物的证据。我们假设，光通过光敏化形成食草动物食物液泡中的活性氧来帮助消化浮游植物猎物。然后，这种活性氧可以降解脂肪和蛋白质，在质量上(通过产生更小的、更容易被同化的化合物)和在数量上(通过提供能量补充)补充消化。我们的数据表明，光辅助消化可以产生2？摄食率提高了10倍，人口增长率提高了20倍。在很低的食物水平下，光辅助消化可以决定以浮游植物为食的异养原生生物的生存和严重死亡。由于原生生物是海洋浮游植物的主要消费者，光辅助消化对浮游植物的消耗、营养再生、营养转移效率和猎物选择的调节具有深远的影响。我们建议研究光在调节原生生物放牧活动中的作用。这项拟议的研究将在多个生物学水平上进行，从食草动物食物液泡中的分子事件到整个浮游植物群落的浮游植物消费调控。这项拟议中的研究围绕着一个令人兴奋的概念，即光作为一种基本的非生物资源，可能会在猎物消化的基本层面上调节海洋中主要食草动物的活动。原生生物的放牧、生长和生长效率与辐射的直接耦合意味着这些速率和效率将以前所未有的方式随深度、纬度和季节而变化。此外，浮游植物种群及其初级消费者之间的耦合程度是群落结构和功能的基本决定因素，可能受到单一非生物资源的强烈影响，因此可能比以前认为的要密切得多。

Light, in conjunction with nutrient supply, is the primary abiotic resource structuring life in the sea. With the exception of various behavioral phenomena such as phototaxis and bioluminescence, light has not been thought to directly influence marine zooplankton energetics. In recent research, we have found evidence for the direct use of light energy in the digestion of phytoplankton by three heterotrophic (non?photosynthetic) protists. We hypothesize that light aids in the digestion of phytoplankton prey through the photosensitized formation of reactive oxygen in grazer food vacuoles. This reactive oxygen may then degrade lipids and proteins, supplementing digestion both qualitatively (by yielding smaller, more readily assimilated compounds) and quantitatively (by providing an energy supplement). Our data indicate that light?aided digestion can result in 2? to 10- fold enhancements of ingestion rate, and up to 20?fold enhancements of population growth rates. At very low food levels, light?aided digestion can make the difference between survival and severe mortality for heterotrophic protists feeding on phytoplankton.Because protists are the primary consumers of phytoplankton in the sea, light?aided digestion has profound consequences for the regulation of phytoplankton consumption, nutrient regeneration, trophic transfer efficiency, and prey selection. We propose an investigation of the role of light in regulating protist grazing activities. The proposed research will be conducted across multiple biological levels, from molecular events in grazer food vacuoles to regulation of phytoplankton consumption in whole microplankton communities. The proposed research centers on the exciting notion that light, a fundamental abiotic resource, may regulate the activities of the ocean's primary herbivores on the fundamental level of prey digestion. A direct coupling of protist grazing, growth, and growth efficiency to irradiance means that these rates and efficiencies will vary with depth, latitude, and season in a heretofore-unsuspected manner. In addition, the degree of coupling between populations of phytoplankton and their primary consumers, a fundamental determinant of community structure and function, could be strongly mediated by a single abiotic resource, and thus might be much closer than previously believed.