RAPID: Sources and Fates of Nitrogen and its Role in Supporting Dinoflagellate Blooms in the Arabian Sea

在过去的几年里，阿拉伯海出现了大规模的鞭毛藻繁殖。这些花以异养双鞭毛藻（Nocticula milaris）为主。此外，在阿曼海岸，去年首次大规模地看到了甲藻Cochlodium polykrikoides。这些藻华现在对海洋的食物网、碳循环和氮循环产生了巨大的影响。初级生产力比以前报道的要高，最低氧区更强，反硝化率非常高。因此，这是一个快速变化的系统，随着气候和富营养化力量变得更加明显，氮的途径和过程可能在未来几年发生重大改变。该项目将通过直接解决支持这些水华的氮的来源和命运问题，补充以前资助的工作，进行初级生产和放牧率测量。具体来说，该项目将与美国、印度和阿曼的同事合作，进行一套过程测量，以评估氮吸收、氮固定和氮循环的速率，并将这些测量结果整合到这个快速变化的系统的更广泛的测量中，以更好地了解支持这些华花的氮动力学。特别值得关注的是蜜夜藻（Nocticula milaris）藻华的出现和扩大，这种藻华在十年前并不存在，但现在对这片海洋的滋养动力学和生物地球化学产生了重大影响。鱼毒性甲藻cochloridium的大规模繁殖仅在去年才出现。该项目为与印度和阿曼科学家建立长期国际合作提供了独特的机会。印度学生将接受15n同位素示踪剂技术培训。此外，REU的一名学生将在2010年夏天被雇用来帮助进行样本和数据分析。希望这名REU学生有兴趣继续他/她的研究，并申请研究生学习，重点关注这些复杂和不断变化的花朵。这项工作将与其他正在进行的努力相结合，向广大学生和公众传达气候变化和富营养化的重要性。

In the past several years, a massive expansion of dinoflagellate blooms has occurred in the Arabian Sea. These blooms are dominated by the heterotrophic dinoflagellates Nocticula milaris. Moreover, along the Oman coast, blooms of the dinoflagellate Cochlodium polykrikoides were seen on a massive scale for the first time last year. These blooms are now are having a large impact on the food web, the carbon cycling, and the nitrogen cycling of this ocean. Rates of primary productivity are higher than previously reported, the oxygen minimum zone is more intense, and denitrification rates are very high. Thus, this is a system that is rapidly changing and one in which nitrogen pathways and processes may be significantly altered in years to come as climate and eutrophication forces become more pronounced. This project will supplement previously funded efforts making primary production and grazing rate measurements by directly addressing the question of the source and fate of nitrogen supporting these blooms. Specifically, this project will conduct, in collaboration with US, Indian and Omani colleagues, a suite of process measurements to assess the rates of nitrogen uptake, nitrogen fixation, and nitrogen cycling, and integrate these measurements into the broader suite of measurements on this rapidly changing system to better understand the nitrogen dynamics supporting these blooms. There is a particular concern over the emergence and expansion of blooms of Nocticula milaris, blooms that were not present a decade ago but which now are having a large impact on the trophodynamics and biogeochemistry of this ocean. Large-scale blooms of the ichthyotoxic dinoflagellate Cochlodinium have only emerged in the past year. This project provides a unique opportunity for establishing long term international collaboration with Indian and Omani scientists. Indian students will be trained in the techniques of15N isotopic tracers. In addition, one REU student will be hired for the summer of 2010 to help with sample and data analysis. It is hoped that this REU student would be interested in furthering his/her studies and would apply for graduate study with a focus on these complex and changing blooms. This work will be integrated and leveraged with other ongoing efforts to convey the importance of climate change and eutrophication to a broad range of students and the public.