Silica Cycling and the Role of Diatoms in the North Pacific Subtropical Gyre

对大西洋硅循环的研究表明，副热带环流占全球海洋二氧化硅产量的13%，但来自北太平洋副热带环流(NPSG)的最新数据显示，副热带环流对二氧化硅产量的贡献要高得多。初步结果还显示，两个环流的季节性二氧化硅生产周期相差几个月。与马尾藻海不同的是，在马尾藻海，硅藻在春季有规律地开花，以应对冬季对流的颠覆，永久层结阻止了NPSG中的春季硅藻开花事件。一年一度的硅藻水华确实出现在NPSG，但令人费解的是，它们发生在夏季，此时层结最强，营养物质浓度处于季节性最低水平。在这个项目中，加州大学圣巴巴拉分校的一名研究人员将研究硅限制强度和二氧化硅溶解强度的季节性变化如何调节NPSG中二氧化硅的年度产生周期，并有助于其独特的季节性。他的假说是，夏季开花期间二氧化硅净产量高的主要原因是NPSG中存在的硅藻物种非常有效的硅酸吸收系统，使它们能够克服硅限制并利用低浓度的硅酸。将与HOT计划合作进行速率测量的时间序列，以确定Aloha站的年度硅循环。该项目还将与夏威夷大学新的“微生物海洋学中心：研究和教育”(CMORE)科学和技术中心合作，研究夏季水华。在更广泛的影响方面，拟议的项目将扩大我们对控制硅藻对开放海洋生态系统中元素循环的贡献的机制的理解。拟议的硅循环研究结合了在Aloha站正在进行的碳、氮和磷循环研究，将第一次有机会对所有这四种元素在一个少营养环流中同时循环进行协调分析。该项目还将开发从二氧化硅生产率实验中量化32Si的新方法。研究生和本科生都将接受培训，国际海洋研究所将与南加州大学海洋科学研究所(MSI)合作，开发与生物碳泵和硅藻在海洋生态系统中的重要性有关的K-12教材，通过MSI的“海洋到课堂”计划。

OCE-0648130Studies of the silicon cycle in the Atlantic Ocean have suggested that subtropical gyres account for 13% of global marine silica production, but more recent data from the North Pacific Subtropical Gyre (NPSG) show much higher rates of silica production that imply an increased contribution of subtropical gyres. Preliminary results also reveal that the seasonal silica production cycles of the two gyres are several months out of phase with each other. Unlike the Sargasso Sea where diatoms bloom regularly in spring in response to winter convective overturn, permanent stratification prevents spring diatom blooms events in the NPSG. Annual diatom blooms do occur in the NPSG, but enigmatically they occur during summer when stratification is strongest and nutrient concentrations are at their seasonal minimum. These enigmatic summer blooms contribute significantly to carbon and nitrogen export in the NPSG and they likely dominate the annual silicon cycle.In this project, a researcher from the University of California at Santa Barbara will investigate how seasonal changes in the intensity of Si limitation and silica dissolution regulate the annual cycle of silica production in the NPSG and contribute to its unique seasonality. His hypothesis is that high rates of net silica production during summer blooms are driven mainly by the extraordinarily efficient silicic acid uptake systems of bloom diatom species present in the NPSG that allow them to overcome Si limitation and exploit low concentrations of silicic acid. Time series of rate measurements will be made in collaboration with the HOT program to define the annual silicon cycle at station ALOHA. The project will also collaborate with the new "Center for Microbial Oceanography: Research and Education" (CMORE) Science and Technology Center at the University of Hawaii to study summer blooms.In terms of broader impacts, the proposed project will expand our understanding of the mechanisms controlling the contribution of diatoms to elemental cycling in open ocean ecosystems. The proposed research on Si cycling combined ongoing studies of C, N and P cycling at station ALOHA will allow, for the first time, an opportunity for a coordinated analysis the cycling of all four of these elements simultaneously in an oligotrophic gyre. The project will also develop new methods to quantify 32Si from silica production rate experiments. Both graduate students and undergraduate students will be trained and the PI will work with UCSB's Marine Science Institute (MSI) to develop K-12 educational materials related to the biological carbon pump and the importance of diatoms in marine ecosystems through MSI's "Oceans to Classroom" program.