SGER: Vertical Migration in Trichodesmium as a Mechanism for Phosphorus Acquisition

SGER：Trichodesmium 中的垂直迁移作为磷获取机制

• 批准号: 9981778
• 负责人: Tracy Villareal
• 金额: $ 4.06万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2001-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9981778&HistoricalAwards=false
• 关键词: SGER; Vertical; Migration; Trichodesmium; Mechanism

The nitrogen-fixing prokaryote Trichodesmium is a widely distributed cyanobacteria in all warm oceans and is the dominant known source of planktonic nitrogen fixation in the ocean. Recent work has documented higher levels of nitrogen fixation by these cyanobacteria than historically reported, but these levels are still inadequate to meet the inputs required by geochemical budgets at oceanic sites.The requirement for phosphorus to support nitrogen fixation is an understudied aspect of this problem. There is little evidence of phosphorus limitation in Trichodesmium despite low inorganic phosphorus concentrations (nanomolar range) at both oceanic time series stations (BATS and HOTS). Trichodesmium can use organic phosphorus, but concentrations are low as well and little is known about Trichodesmium's use of these pools.One possible phosphorus source is migration to pools beneath the nutricline. Vertical migration has been documented in several non-flagellated eukaryotes in the open sea to provide access to subsurface nitrogen sources. Trichodesmium is known to buoyancy regulate and has the ascent/descent rates to accomplish such a migration for phosphorus. However, there is contradictory evidence as to whether migration occurs from both in physiological and compositional data.The objective of this project is to examine the characteristics of Trichodesmium spp. in the field to determine if migration is actually occurring. Composition and rate measures to determine this include respiration rates, carbohydrate, protein, polyphosphate, CHN, particulate P, trichome buoyancy, and fluorescence yield via PAM fluorometry. Based on models of vertically migrating eukaryotes, these measures should vary predictably and significantly between ascending and descending cells if P-replenishment is occurring at depth. The program will utilize a Trichodesmium cruise previously funded off of Australia, and 1 cruise in the Gulf of Mexico to compare different populations. The project is not site specific, but rather is evaluating a behavior that has significant implications at both the BATS and HOTS stations.At the conclusion of the project, the migration capacity of Trichodesmium will be confirmed or refuted. This will permit direct assessment of the role of vertical migration for P acquisition in supporting nitrogen fixation in the ocean and will be a significant advance in understanding the ecology of this important genus.

固氮原核生物束毛藻（Trichodesmium）是一种广泛分布于所有温暖海洋中的蓝藻，是海洋中主要的固氮来源。最近的工作记录了这些蓝藻固氮水平比历史上报道的更高，但这些水平仍然不足以满足地球化学预算所需的投入在海洋sites.The要求磷，以支持固氮是一个未充分研究的方面这个问题。尽管在两个海洋时间序列站（BATS和HOTS）的无机磷浓度低（纳摩尔范围），但几乎没有证据表明束毛藻属的磷限制。束毛藻可以利用有机磷，但浓度很低，而且对束毛藻利用这些有机磷池知之甚少。一个可能的磷源是迁移到营养线下的有机磷池。垂直迁移已被记录在几个无鞭毛的真核生物在公海，以提供访问地下氮源。束毛藻是已知的浮力调节，并具有上升/下降速率，以完成这样的磷迁移。然而，从生理学和成分学的数据来看，关于迁移是否发生的证据是相互矛盾的。以确定是否确实发生了移民。确定这一点的组成和速率测量包括呼吸速率、碳水化合物、蛋白质、多磷酸盐、CHN、颗粒P、毛状体浮力和通过PAM荧光测定法的荧光产率。垂直迁移的真核生物模型的基础上，这些措施应该有不同的可预测性和显着的上升和下降的细胞之间，如果P-补给发生在深度。该计划将利用之前由澳大利亚资助的Trichodesmium巡航，以及墨西哥湾的1次巡航来比较不同的种群。该项目不是特定地点的，而是评估在BATS和HOTS站都有重大影响的行为。在项目结束时，束毛藻的迁移能力将得到证实或反驳。这将允许直接评估的作用，垂直迁移的P收购在支持海洋中的固氮，并将是一个重要的进展，在了解这个重要的属的生态。