Selective feeding by mucous-net filter feeders on the ocean's smallest organisms

海洋表面主要由称为微微型浮游生物的微观植物和动物组成，它们位于海洋食物网的底部。水母类的动物被称为水母类动物，它们专门以这些微型生物为食，它们用粘液制成的网过滤大量的水。在过去，人们认为，食虫动物吃任何通过粘液网的东西，但新的工作表明，进食可能是有选择性的。海洋中最丰富的微生物群，称为SAR 11，似乎逃避了apappherularian，而类似大小的光合微生物被捕获。 本研究将在美国俄勒冈州和法国滨海自由城进行一系列的实验室和田间试验，以揭示选择性的机制。该研究将测试颗粒形状（例如球形与椭圆形）的影响，颗粒对粘液网的粘附特性以及流体动力学的作用。它将侧重于世界性的浮游生物Oikopleura dioica，一个重要的微型浮游生物食草动物。结果将是重要的了解粘液网滤食性动物在塑造海洋的微生物群落的结构，以及生物地球化学循环的作用。该项目将支持一名早期职业教师，将为一名博士生和两名本科生提供培训和指导，涉及与法国和以色列的科学家合作，并将通过在哈特菲尔德海洋科学游客中心和查尔斯顿海洋生物中心展出的展品和图像吸引公众。 微型浮游生物的密度高达每毫升100万，在数量上占主导地位的上层海洋猎物场。由于apapecularians影响皮科和纳米颗粒通量通过其高过滤率和生产的粘液聚集体，选择性放牧将有重要的影响微生物循环动力学和垂直通量。因此，这项工作将提供深入了解上层海洋浮游细菌群落结构的机制，并增加对微生物-后生动物食物网在浅海和海洋生态系统中相互作用的理解。 该项目的具体目标是：a）使用微粒子图像测速法确定流动形态在调节自由游泳的附着生物室内颗粒捕获方面的作用，B）确定颗粒形状对附着生物截留效率的影响，并比较合成颗粒和生物颗粒之间的这种影响，和c）量化粘滤装置上的颗粒粘附，以确定微型浮游生物细胞表面性质是否影响粘网滤食性动物的截留效率。

The surface of the ocean is dominated by microscopic plants and animals called picoplankton, which are at the base of the marine food web. Jelly-like animals called appendicularians specialize in feeding on these miniature organisms by filtering large quantities of water using nets made out of mucus. In the past, it was thought that appendicularians eat anything that passes through the mucous net, but new work shows that feeding may be selective. The most abundant group of microorganisms in the ocean, called SAR 11, seems to evade the appendicularian, while similar-sized photosynthetic microbes are captured. In this study, a series of lab and field experiments will be conducted in Oregon, USA, and Villefranche-sur-mer, France, to uncover the mechanisms for selectivity. The research will test the effect of particle shape (e.g. spherical vs. ellipsoidal), adhesion properties of particles to mucous meshes, and the role of hydrodynamics. It will focus on the cosmopolitan appendicularian Oikopleura dioica, an important grazer of picoplankton. Results will be important for understanding the role of mucous-net filter feeders in shaping the structure of the ocean's microbial community as well as biogeochemical cycling. The project will support an early-career faculty member, will provide training and mentoring for one PhD student and two undergraduates, involves collaboration with scientists in France and Israel, and will engage the public through exhibits and images to be displayed at the Hatfield Marine Science Visitor Center and Charleston Marine Life Center. Picoplankton occur at densities of up to a million per mL and numerically dominate the upper ocean prey field. Since appendicularians influence pico- and nano-particle flux through their high filtration rates and the production of mucous aggregates, selective grazing will have important ramifications for microbial loop dynamics and vertical flux. Therefore, this work will provide insights into the mechanisms governing bacterioplankton community structure in the upper ocean and increase understanding of microbial-metazoan food web interactions in both neritic and oceanic ecosystems. The specific goals of the project are to a) determine the role of flow morphology in regulating particle capture within the houses of free-swimming appendicularians using micro-Particle Image Velocimetry, b) determine the effect of particle shape on retention efficiencies by appendicularians, and compare this effect between synthetic and biological particles, and c) quantify particle adhesion to the mucous filtration apparatus in order to determine if picoplankton cell surface properties influence retention efficiencies by mucous-net filter-feeders.