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Trichodesmium是一种广泛分布在所有温暖海洋中的蓝细菌，是海洋中浮游固氮的主要已知来源。最近的工作记录了这些蓝藻的固氮水平比历史报道的要高，但这些水平仍然不足以满足海洋地点地球化学预算所需的投入。支持固氮所需的磷是这个问题的一个尚未得到充分研究的方面。尽管两个海洋时间序列站（BATS 和 HOTS）的无机磷浓度较低（纳摩尔范围），但几乎没有证据表明木藻中的磷受到限制。毛藻可以利用有机磷，但浓度也很低，而且人们对毛藻对这些池的利用知之甚少。一种可能的磷源是迁移到营养线以下的池中。已记录了公海中几种无鞭毛真核生物的垂直迁移，以提供获取地下氮源的途径。已知毛藻具有浮力调节功能，并具有完成磷迁移的上升/下降速率。然而，关于迁移是否发生从生理和成分数据来看，存在相互矛盾的证据。该项目的目的是检查 Trichodesmium spp 的特征。在现场确定迁移是否确实发生。确定这一点的成分和速率测量包括呼吸速率、碳水化合物、蛋白质、多磷酸盐、CHN、颗粒磷、毛状体浮力和通过 PAM 荧光测定法的荧光产量。根据垂直迁移真核生物的模型，如果磷补充发生在深度，这些测量值在上升细胞和下降细胞之间应该有可预测的显着变化。该计划将利用之前在澳大利亚资助的一次Trichodesmium游轮和在墨西哥湾的一次游轮来比较不同的种群。该项目不是针对特定地点的，而是评估对 BATS 和 HOTS 站都有重大影响的行为。在项目结束时，将证实或反驳毛藻的迁移能力。这将允许直接评估垂直迁移对获取磷在支持海洋固氮方面的作用，并将是了解这一重要属的生态学的重大进步。