Collaborative Research: Investigating Iron-inding Ligands in Southern Ocean Diatom Communities: The Role of Diatom-Bacteria Associations

合作研究：调查南大洋硅藻群落中的铁配体：硅藻-细菌协会的作用

• 批准号: 1443483
• 负责人: Kristen Buck
• 金额: $ 27.66万
• 依托单位: University of South Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-15 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1443483&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Iron; inding

This project focuses on an important group of photosynthetic algae in the Southern Ocean (SO), diatoms, and the roles associated bacterial communities play in modulating their growth. Diatom growth fuels the SO food web and balances atmospheric carbon dioxide by sequestering the carbon used for growth to the deep ocean on long time scales as cells sink below the surface. The diatom growth is limited by the available iron in the seawater, most of which is not freely available to the diatoms but instead is tightly bound to other compounds. The nature of these compounds and how phytoplankton acquire iron from them is critical to understanding productivity in this region and globally. The investigators will conduct experiments to characterize the relationship between diatoms, their associated bacteria, and iron in open ocean and inshore waters. Experiments will involve supplying nutrients at varying nutrient ratios to natural phytoplankton assemblages to determine how diatoms and their associated bacteria respond to different conditions. This will provide valuable data that can be used by climate and food web modelers and it will help us better understand the relationship between iron, a key nutrient in the ocean, and the organisms at the base of the food web that use iron for photosynthetic growth and carbon uptake. The project will also further the NSF goals of training new generations of scientists and of making scientific discoveries available to the general public. The project supports early career senior investigators and the training of graduate and undergraduate students as well as outreach activities with middle school Girl Scouts in Rhode Island, inner city middle and high school age girls in Virginia, and middle school girls in Florida.The project combines trace metal biogeochemistry, phytoplankton cultivation, and molecular biology to address questions regarding the production of iron-binding compounds and the role of diatom-bacterial interactions in this iron-limited region. Iron is an essential micronutrient for marine phytoplankton. Phytoplankton growth in the SO is limited by a lack of sufficient iron, with important consequences for carbon cycling and climate in this high latitude regime. Some of the major outstanding questions in iron biogeochemistry relate to the organic compounds that bind 99.9% of dissolved iron in surface oceans. The investigators' prior research in this region suggests that production of strong iron-binding compounds in the SO is linked to diatom blooms in waters with high nitrate to iron ratios. The sources of these compounds are unknown but the investigators hypothesize that they may be from bacteria, which are known to produce such compounds for their own use. The project will test three hypotheses concerning the production of these iron-binding compounds, limitations on the biological availability of iron even if present in high concentrations, and the roles of diatom-associated bacteria in these processes. Results from this project will provide fundamental information about the biogeochemical trigger, and biological sources and function, of natural strong iron-binding compound production in the SO, where iron plays a critical role in phytoplankton productivity, carbon cycling, and climate regulation.

该项目重点关注南大洋 (SO) 中一组重要的光合藻类、硅藻，以及相关细菌群落在调节其生长中所发挥的作用。当细胞沉入地表以下时，硅藻的生长会长期将用于生长的碳封存到深海，从而为SO食物网提供燃料并平衡大气中的二氧化碳。硅藻的生长受到海水中可用铁的限制，其中大部分铁不能自由地提供给硅藻，而是与其他化合物紧密结合。这些化合物的性质以及浮游植物如何从中获取铁对于了解该地区和全球的生产力至关重要。研究人员将进行实验来表征公海和近海水域中硅藻、其相关细菌和铁之间的关系。实验将涉及以不同的营养比例向天然浮游植物组合提供营养，以确定硅藻及其相关细菌如何响应不同的条件。这将为气候和食物网建模者提供有价值的数据，并将帮助我们更好地了解铁（海洋中的一种关键营养物质）与食物网底部利用铁进行光合作用生长的生物之间的关系和碳吸收。该项目还将进一步推进国家科学基金会培养新一代科学家和向公众提供科学发现的目标。该项目支持早期职业高级调查员、研究生和本科生的培训，以及与罗德岛州中学女童子军、弗吉尼亚州内城初中和高中适龄女孩以及佛罗里达州初中女孩的外展活动。该项目结合了痕量金属生物地球化学、浮游植物培养和分子生物学，以解决有关铁结合化合物的产生以及硅藻-细菌相互作用在该铁限制区域中的作用的问题。铁是海洋浮游植物必需的微量营养素。由于缺乏足够的铁，浮游植物的生长受到限制，这对高纬度地区的碳循环和气候产生了重要影响。铁生物地球化学中的一些主要悬而未决的问题与结合海洋表层 99.9% 溶解铁的有机化合物有关。研究人员之前在该地区的研究表明，SO 中强铁结合化合物的产生与硝酸盐与铁比率较高的水域中硅藻的大量繁殖有关。这些化合物的来源尚不清楚，但研究人员推测它们可能来自细菌，已知细菌会产生此类化合物供自己使用。该项目将测试三个假设，涉及这些铁结合化合物的生产、铁的生物利用度的限制（即使铁的浓度很高）以及硅藻相关细菌在这些过程中的作用。该项目的结果将提供有关 SO 中天然强铁结合化合物生产的生物地球化学触发因素、生物来源和功能的基本信息，其中铁在浮游植物生产力、碳循环和气候调节中发挥着关键作用。