MCA: Developing transcriptomics as a tool to investigate toxic diatom responses to ocean heatwave and upwelling events

假尼齐亚硅藻在美国西海岸形成了大量有毒有害的藻华，杀死了野生动物，损害了宝贵的海洋渔业。无论是现在还是未来不断变化的气候条件下，了解这些水华的原因并预测它们的发生，对沿海地区的环境和经济健康都至关重要。令人费解的是，这些藻华似乎发生在沿海海水上涌导致寒冷、营养丰富、pH值低的海面条件的时期，也发生在热浪事件导致温暖、营养贫乏、pH值高的时期。据预测，随着气候变化，这两种极端情况将变得更加严重。这个项目是通过实验测试伪nitzschia对上升流和热浪事件的反应，通过测量细胞生长、毒素产生和基因表达。该项目的更广泛影响包括对首席研究员进行新的基因表达方法培训、研究生和本科生研究培训、高中研究指导经验以及针对商业捕鱼业的推广和交流活动。社会效益包括更好地了解破坏性有毒藻华的原因，以及它们在未来沿海海洋中的变化。有毒硅藻伪硝藻（pseudonitzschia）每年都会在美国西海岸造成有害的水华，在这个地区，风力驱动的上升流将丰富的营养物质带入了光区。然而，该地区也正在经历与全球变暖有关的前所未有的间歇性海洋热浪事件。因此，该地区未来的气候趋势表明，在较冷、营养更丰富、pH值较低的上升流和较暖、营养更枯竭、pH值较高的热浪之间，当前的物理化学极端现象将会被夸大。令人惊讶的是，有毒的伪nitzschia可以在上升流和热浪条件下繁殖，尽管在营养、温度和碳酸盐化学等关键环境控制方面有相反的趋势。这个项目是通过首先获得两个伪尼茨氏菌分离株的每个单独因素，温度，二氧化碳分压，磷，氮和硅的完整响应曲线来测试这是如何发生的。然后，将这些变量结合在整体上升流和热浪情景孵育实验中，以比较培养和自然开花对伪尼茨奇亚生长和毒性的影响。PI正在利用她在藻类生理学方面的现有专业知识评估这些实验中的有毒硅藻反应，并通过扩大她的专业视野，与罗德岛大学的Bethany Jenkins博士合作开发转录组生物信息学方面的新技能。通过实验测试拟nitzschia在模拟上升流或热浪发生时对营养物质浓度、温度和二氧化碳分压变化的生理反应，并测量毒素合成途径等关键代谢途径基因的表达。该项目有助于理解和解释有毒伪nitzschia在不断变化的海洋中令人惊讶的生态位灵活性，同时为PI未来的职业发展提供了新的途径。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The diatom Pseudo-nitzschia forms large, toxic harmful algal blooms along the U.S. West Coast, killing wildlife and harming valuable ocean fisheries. Understanding the causes of these blooms and predicting their occurrence, both now and under future changing climate conditions, is critical to coastal environmental and economic health. Puzzlingly, these blooms seem to happen during periods when coastal seawater upwelling results in cold, nutrient-rich, low pH sea surface conditions, and also during times when heat wave events cause warm, nutrient-poor, high pH conditions. These two extremes are forecast to get even more intense with climate change. This project is experimentally testing how Pseudo-nitzschia responds to upwelling and heat wave events using measurements of cell growth, toxin production, and gene expression. Broader impacts of this project include training the principal investigator in new gene expression methods, graduate and undergraduate research training, high school research mentoring experiences, and outreach and communications activities aimed at the commercial fishing industry. Societal benefits include obtaining a better understanding of the causes of damaging toxic algal blooms, and how they may change in the future coastal ocean. The toxic diatom Pseudo-nitzschia causes annual harmful blooms along the US West Coast, a region where wind-driven upwelling brings rich nutrient supplies into the euphotic zone. However, this region is also experiencing unprecedented episodic ocean heatwave events linked to global warming. Thus, future climate trends in this region suggest an exaggeration of current physio-chemical extremes between colder, more nutrient-rich, low pH upwelling, and warmer, more nutrient-depleted, higher pH heatwaves. Surprisingly, toxic Pseudo-nitzschia spp. can bloom under both upwelling and heatwave conditions, despite opposite trends in key environmental controls like nutrients, temperature, and carbonate chemistry. This project is testing how this happens by first obtaining full response curves for each of the individual factors, temperature, pCO2, phosphorus, nitrogen, and silicon for two Pseudo-nitzschia isolates. Then, these variables are combined in holistic upwelling and heatwave scenario incubation experiments, to compare how growth and toxicity is affected in both cultures and natural blooms of Pseudo-nitzschia. The PI is assessing toxic diatom responses in these experiments using her existing expertise in algal physiology, as well as by expanding her professional horizons to develop new skills in transcriptome bioinformatics in partnership with Dr. Bethany Jenkins from the University of Rhode Island. Experiments are conducted to test the physiological responses of Pseudo-nitzschia to changes in nutrient concentrations, temperature and pCO2 during simulated upwelling or heatwave occurrences, and measure expression of key metabolic pathway genes such as toxin synthesis pathways. This project is helping to understand and interpret the surprising niche flexibility of toxic Pseudo-nitzschia in a changing ocean, and at the same time offers the PI a new avenue forward for her future career development.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.