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?

有毒赤潮甲藻Gymatriiniumbreve的水华是佛罗里达陆架生态系统的重要特征。水华出现在佛罗里达西部近海18-75公里的贫营养中陆架区。然而，这些沃茨的特点是溶解的无机氮和有机氮（DIN和DON）的浓度都很低，目前还不清楚G。短花满足了它们生长对氮的需求。环境氮浓度，模型预测，和化学计量计算的营养需求的基础上观察到的生物量的增长表明，N输入fromriverine，上升流和原位N再生是不足以支持所观察到的G。在这一地区的短枝花。此外，未发表的研究，轶事信息和历史赤潮监测数据表明，G。短花和丝状固氮蓝藻Trichodesmium spp.在墨西哥湾和大西洋沿岸沃茨。很少有人知道的命运和意义，新的N输入来自最近固定的N2或营养转移的途径，使这一新的N被同化到贫营养海洋生态系统。确定贫营养系统中新氮的去向以及来自N2固定的氮输入对群落结构和功能的影响是至关重要的，这样我们就可以准确地评估新氮对再生和输出生产的影响。是一个理想的模式系统，在其中研究的命运新的N输入固氮束毛藻属。以及促进该N营养转移的途径。我们还认为G.短在西佛罗里达陆架沃茨的支持释放和再生的DIN和DON从N2最近固定的共同发生或之前开花的束毛藻属。 本研究将通过为期三年的实验室和田间研究来验证这些假设，以：1）确定G.短音符; 2）确定从束毛藻固定的N2中直接或间接再生NH 4+和DON是否提供了足够的N底物来支持G.和3确定相关的社区和研究营养途径，使新固定的N2来自束毛藻属。刺激在其它贫营养沃茨中的生产。将积极与建模项目合作，重点是束毛藻和G。在西佛罗里达大陆架地区的短枝花。

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 Furthermore, unpublished research, anecdotal information and historical red tide monitoring data suggest a correlation between the timing and magnitude of G. breve blooms and the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 we can accurately assess the impact of new N on regenerated and export production.We propose that the oligotrophic west Florida Shelf ecosystem, which is characterized by large blooms of these species, 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. We also suggest that 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.