Collaborative Research: Fate of Recently Fixed N2 in the Eastern Gulf of Mexico: Does the Regeneration of N by Trichodesmium Support the Development of Gymnodinium Breve Blooms?

合作研究：墨西哥湾东部最近固定的 N2 的命运：Trichodesmium 的 N 再生是否支持裸甲藻开花的发展？

• 批准号: 0095940
• 负责人: Deborah Bronk
• 金额: $ 10.99万
• 依托单位: College of William & Mary Virginia Institute of Marine Science
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-05-01 至 2004-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0095940&HistoricalAwards=false
• 关键词: Collaborative; Research; Fate; Recently; Fixed

Blooms of the toxic red tide dinoflagellate, Gymnodinium breve, are an important feature of the Florida Shelf ecosystem. Blooms appear to initiate and develop in an oligotrophic, mid-shelf region 18-75 km offshore of west Florida. However, these waters are characterized by low concentrations of both dissolved inorganic and organic nitrogen (DIN and DON), and it is unclear how G. breve blooms meet their N demand for growth. Ambient N concentrations, model predictions, and stoichiometric calculations of nutrient requirements for growth based on observed biomass suggest that N inputs fromriverine, upwelling and in situ N regeneration are insufficient to support the observed G. breve blooms in this region. Furthermore, unpublished research, anecdotal information and historical red tide monitoring data suggest a correlation between the timing and magnitude of G. breve blooms and the occurrence of the filamentous, N2 fixing cyanobacteria, Trichodesmium spp. in both the Gulf of Mexico and Atlantic coastal waters. Little is known about the fate and significance of new N inputs derived from recently fixed N2 or of the pathways of trophic transfer whereby this new N is assimilated into oligotrophic marine ecosystems. It is critical to determine the fate of new N in oligotrophic systems and the effects of N inputs from N2 fixation on the community structure and function so that one can accurately assess the impact of new N on regenerated and export production.The oligotrophic west Florida Shelf ecosystem is an ideal model system in which to examine the fate of new N inputs from N2 fixation by Trichodesmium spp. and the pathways facilitating the trophic transfer of this N. This project will examine the idea that blooms of G. breve in west Florida shelf waters are supported by the release and regeneration of DIN and DON from N2 recently fixed by co-occurring or preceding blooms of Trichodesmium spp. The present project will examine these hypotheses with a three-year program consisting of laboratory and field studies to: 1) determine the capacity for and kinetics of N uptake and regeneration by G. Breve; 2) determine whether direct or indirect regeneration of NH4+and DON from recently fixed N2 by Trichodesmium provides sufficient N substrates to support the observed growth of G. Breve; and 3 identify associated communities and examine trophic pathways whereby newly fixed N2 derived from Trichodesmium spp. stimulates production in otherwise oligotrophic waters. There will be active collaboration with modeling projects focused on both Trichodesmium and G. breve blooms in the west Florida shelf region.

有毒赤潮甲藻的大量繁殖是佛罗里达州大陆架生态系统的一个重要特征。水华似乎是在佛罗里达州西部离岸18-75公里的一个少营养的中陆架地区开始和发展的。然而，这些水域的特点是溶解的无机和有机氮(DIN和DON)浓度较低，目前尚不清楚短藻水华如何满足其生长对N的需求。根据观测到的生物量，环境氮浓度、模型预测和对生长所需营养物质的化学计量计算表明，来自河流、上升流和原位氮再生的氮输入不足以支持该地区观测到的短水华。此外，未发表的研究、轶事信息和历史红潮监测数据表明，短藻水华的时间和规模与丝状、固定氮气的蓝藻Trichodesum spp的出现之间存在相关性。在墨西哥湾和大西洋沿岸水域。关于从最近固定的氮气中获得的新的N输入的命运和意义，或者这些新的N被同化到少营养海洋生态系统中的营养转移途径，人们知之甚少。确定新氮在贫营养系统中的去向，以及固氮输入对群落结构和功能的影响，是准确评估新氮对再生和出口产品的影响的关键。西佛罗里达陆架生态系统是研究木霉固氮新输入的命运的理想模式系统。以及促进这一N的营养转移的途径。本项目将检验这样一种观点，即在佛罗里达州西部陆架水域中，短毛木霉的水华是由DIN和DON的释放和再生支持的，而N2中的DIN和DON最近被共生或先于Trichodesum spp的水华修复。本项目将通过一个由实验室和田间研究组成的为期三年的计划来检验这些假设：1)确定G.Breve吸收和再生N的能力和动力学；2)确定Trichodesum从最近固定的N2中直接或间接再生NH4+和DON是否提供了足够的N底物来支持G.Breve的生长；以及3识别相关的群落并检查来自Trichodesum spp的新固定的N的营养途径。刺激其他营养不足的水域的产量。将与专注于西佛罗里达州陆架地区的毛霉和短毛藻的建模项目积极合作。