How does intensity and frequency of environmental variability affect phytoplankton growth?

被称为浮游植物的微观植物是全球海洋生态系统的关键成员，因为它们的光合作用支持大部分海洋食物链，并产生与陆地植物一样多的氧气。正因为如此，海洋学家经常进行实验，研究温度和二氧化碳水平等因素如何影响浮游植物的生长。以前的大多数实验都使用恒定的温度和二氧化碳水平，但从观察真实海洋生态系统的测量结果可以清楚地看出，这两个因素在几天到几周的时间尺度上往往变化很大。利用野外和实验室实验以及计算机建模，该项目将测试几个主要浮游植物群体在恒定温度和二氧化碳条件下的生长差异，与这些因素在强度和频率上波动的条件相比。这项研究将使海洋科学家更好地了解浮游植物如何对今天和未来不断变化的自然环境作出反应，从而帮助我们了解海洋食物网如何发挥作用，以支持渔业等重要生物资源。该项目将培养研究生和本科生以及一名博士后研究员，主要科学家将参与一项海洋科学教育计划，该计划主要面向洛杉矶市中心学区的少数民族高中生。该项目的目标是利用实验室培养和自然群落实验来了解实际波动的温度和二氧化碳分压条件如何以不同于以前工作中使用的人工恒定暴露的方式影响全球重要的浮游植物群。培养实验将测试短期热波动和碳酸盐波动的强度和频率如何影响重氮营养型和微浮游蓝藻、球石藻和硅藻在当前和预计的未来环境条件下的生长反应。这些实验结果将通过加利福尼亚上升流状态的混合自然组合的平行实验来支持和扩展，使我们能够使用浮游植物群落来测试这些相同的问题，浮游植物群落在春季上升流季节经历了高度动态的热系统和碳酸盐系统条件之间的巨大季节性变化，而在秋季分层事件期间相对更静态的条件。这些结果将使用新一代的数值模型进行综合，这些模型采用新颖的方法来结合现实的环境变化，以便更准确地预测浮游植物对当今海洋生态系统动态环境的反应，以及未来变化的海洋。

Microscopic plants called phytoplankton are key members of global oceanic ecosystems, since their photosynthesis supports the majority of the marine food chain and produces about as much oxygen as land plants. Because of this, oceanographers have often carried out experiments examining how factors such as temperature and carbon dioxide levels may affect phytoplankton growth. Most previous experiments have used constant levels of temperature and carbon dioxide, but it is clear from looking at measurements from real ocean ecosystems that these two factors often vary greatly over timescales of days to weeks. Using field and laboratory experiments along with computer modeling, this project will test how the growth of several major groups of phytoplankton differs under constant conditions of temperature and carbon dioxide, compared to conditions in which these factors fluctuate in intensity and frequency. This research will give marine scientists a better picture of how phytoplankton may respond to a varying natural environment today and in the future, and therefore help us to understand how ocean food webs function to support critical living resources such as fisheries. The project will train graduate and undergraduate students and a postdoctoral researcher, and the lead scientists will be involved in an ocean science education program for largely minority high school students from a downtown Los Angeles school district.The goal of this project is to use laboratory culture and natural community experiments to understand how realistically fluctuating temperature and pCO2 conditions may affect globally important phytoplankton groups in ways that differ from the artificial constant exposures used in previous work. Culture experiments will test how the intensity and frequency of short-term thermal and carbonate fluctuations affects the growth responses of diazotrophic and picoplanktonic cyanobacteria, coccolithophores, and diatoms under both current and projected future environmental conditions. These lab results will be supported and extended by parallel experiments using mixed natural assemblages from the California upwelling regime, allowing us to test these same questions using phytoplankton communities that experience large seasonal shifts between highly dynamic thermal and carbonate system conditions during the spring upwelling season, and relatively much more static conditions during fall stratification events. These results will be synthesized using a new generation of numerical models that employ novel approaches to incorporating realistic environmental variations to allow more accurate predictions of phytoplankton responses to a dynamic environment in today's marine ecosystems, and in the future changing ocean.