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

硅藻伪菱形藻在美国西海岸形成大量有毒的有害藻类，杀死野生动物，损害宝贵的海洋渔业。了解这些水华的原因并预测它们的发生，无论是现在还是在未来不断变化的气候条件下，都对沿海环境和经济健康至关重要。令人费解的是，这些水华似乎发生在沿海海水上升流导致寒冷、营养丰富、低pH值海面条件的时期，也发生在热浪事件导致温暖、营养不良、高pH值条件的时期。据预测，随着气候变化，这两个极端将变得更加激烈。这个项目正在通过测量细胞生长、毒素生产和基因表达来实验测试伪菱形藻如何对上升流和热浪事件做出反应。该项目的更广泛影响包括对首席调查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外联和交流活动。社会利益包括更好地了解有害有毒藻类大量繁殖的原因，以及它们可能如何在未来的沿海海洋中发生变化。有毒的硅藻伪菱形藻导致美国西海岸一年一度的有害水华，该地区由风力驱动的上升流将丰富的营养供应带入真光带。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，目前在更冷、更丰富的营养物质、低pH值上升流和更温暖、更养分消耗、更高pH值热浪之间的物理化学极端被夸大了。令人惊讶的是，有毒的伪菱形藻。可以在上升流和热浪条件下开花，尽管在营养、温度和碳酸盐化学等关键环境控制方面存在相反的趋势。该项目正在测试这是如何发生的，首先获得温度、二氧化碳、磷、氮和硅这两个假硝化细菌分离株的每个单独因素的完整响应曲线。然后，将这些变量结合在整体上升流和热浪情景孵化实验中，比较假菱形藻在培养和自然繁殖中的生长和毒性是如何受到影响的。PI正在利用她在藻类生理学方面的现有专业知识，以及通过扩大她的专业视野，与罗德岛大学的Bathany Jenkins博士合作开发转录组生物信息学方面的新技能，来评估这些实验中的有毒硅藻反应。在模拟上升流或热浪发生的过程中，通过实验测试了拟菱形藻对营养物质浓度、温度和二氧化碳浓度变化的生理响应，并测量了关键代谢途径基因的表达，如毒素合成途径。这个项目正在帮助理解和解释有毒伪硝酸盐在不断变化的海洋中令人惊讶的利基灵活性，同时也为PI未来的职业发展提供了一条新的途径。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.