Collaborative Research: The Ecological Impact of Mixotrophic Algae in a Changing Arctic Marine Climate

大多数生物体仅通过光合作用（光养）或仅通过有机物质的摄入/同化（异养）来满足其碳和能量需求。然而，人们越来越认识到，混合营养生物将光养和异养结合在一个生物体中，是浮游食物网的重要组成部分。 根据之前的工作，研究人员已经证实了北极和南极水域中混合营养生物的普遍存在，并假设北极地表水变暖的可能后果是该地区的微微和纳米混合营养生物将变得更加丰富。 研究人员将使用来自北极各地的水样进行实验室实验，以更好地了解引发混合营养活动的环境条件。 此类实验还将提供有关微生物食物网如何在气候变暖中发挥作用以及这些变化将如何影响较高营养级（例如鱼类）的信息。这项工作将为我们目前对不断变化的北极地表水食物网结构、动态和养分流的看法提供可能的变革性重新定位。 该项目将培养博士后科学家、研究生和本科生。 此外，该项目还包括向费城市区的当地学校进行推广，以及与马萨诸塞州法尔茅斯市的合作。高中艺术教师作为新颖艺术科学项目（STEAM）的一部分。随着北极水温变暖，研究人员预测会对海洋食物网产生双重影响。 首先，他们预测微微型和纳米型浮游植物对初级生产的贡献将会增加。 其次，他们预测由于许多超微型和纳米浮游植物物种表现出混合营养行为，因此会对细菌消耗产生影响。 研究人员提出了对北极水域中发现的混合营养型藻类菌株进行多项实验室实验。 北极海洋分离物将从罗斯科夫培养物保藏中心和国家海洋藻类中心获得。 物种特定的混合营养活动和放牧率将在一系列触发和/或刺激混合营养的环境条件下确定，例如高/低光照和高/低营养物质。 根据这些特定物种的测量结果，以及用于确定整个北极海洋环境水样中物种丰度的 qPCR 分析，可以在整个北极范围内评估混合营养活动的潜在影响。 最后，为了在不依赖摄入实验的情况下确定和比较环境样品中的混合营养活性水平，研究人员将开发一种基于基因的活性方法，该方法基于 RNA 测序和上述环境响应实验的结果。 这对于全球变暖的预测非常重要。

Most organisms meet their carbon and energy needs solely on photosynthesis (phototrophy) or solely on ingestion/assimilation of organic substances (heterotrophy). However, there is increasing recognition that mixotrophs, which combine phototrophy and heterotrophy in a single organism, are important components of planktonic food webs. Based on prior work, the investigators have confirmed the ubiquitous nature of mixotrophs in Arctic and Antarctic waters and hypothesize that a possible consequence to the warming of Arctic surface waters is that pico- and nano-mixotrophs will become more abundant in the region. Using water samples from across the Arctic, the investigators will conduct laboratory experiments to better understand the environmental conditions that trigger mixotrophic activity. Such experiments will also provide information on how the microbial food web will function in a warming climate and how such changes will potentially affect higher trophic levels, such as fish. This work will provide a possibly transformative re-orienting of our current view of surface water food webs structure and dynamics and nutrient flows in a changing Arctic. The project will train a post doctoral scientist, graduate, and undergraduate student. In addition, the project includes outreach to local schools in urban Philadelphia, and collaboration with a Falmouth, MA. high school art teacher as part of novel art-science projects (STEAM).As Arctic water temperatures warm, the investigators predict a two-fold effect on the marine food web. First, they predict an increased contribution to primary production from pico- and nano-phytoplankton. Second, they predict an impact on bacterial consumption owing to the fact that many of the pico- and nano-phytoplankton species exhibit mixotrophic behavior. The investigators propose a number of laboratory experiments on strains of algal groups that have been identified as mixotrophic species and are found in Arctic waters. Arctic marine isolates will be acquired from the Roscoff Culture Collection and the National Center of Marine Algae. Species specific mixotrophic activity and grazing rates will be determined across a range of environmental conditions that trigger and/or stimulate mixotrophy, such as high/low light and high/low nutrients. From these species specific measurements, along with qPCR analysis to determine species abundances in water samples from across the Arctic marine environment, the potential impact of mixotrophic activity can be assessed on an Arctic-wide basis. Finally, to determine and compare the levels of mixotrophic activity in environmental samples without relying on ingestion experiments the investigators will develop a gene-based method of activity based upon RNA sequencing and the results of the environmental response experiments discussed above. This will be important for prediction in a warmer world.