Collaborative Research: SOFeX: Mesoscale Iron fertilization Effects on Plankton Community Structure, Phytoplankton Growth and Zooplankton Grazing

南大洋是了解海洋在全球碳循环中的作用及其调节气候变化潜力的关键区域。除了是大气碳高流入和深水形成的地区外，南极环极水域主要营养物质的持续高密度是海洋中最大的未实现初级生产潜力的池。该项目是一项更大的努力的一部分，目的是检验这样一个假设，即铁的可获得性限制了南大洋浮游植物的生产和生物量积累、营养物质的利用和二氧化碳的减少。Landry、Chisholm和Bidigare博士将通过研究铁的富集度和硅酸盐的有效性对浮游生物群落的物种组成和大小结构以及浮游植物的特定类群生长速度和荧光反应的影响做出贡献。浮游生物群落的功能和分类成分，从细菌到中浮游生物，将通过结合流式细胞术、特定分类群的色素、视频图像分析显微镜和浮游生物光学计数来量化。此外，他们将使用稀释和肠道荧光技术来确定微型和中型浮游动物对放牧的贡献，并评估放牧作为防止部分或全部浮游植物种群显著净增长的替代控制机制。这项研究将从社区的角度解释这些现场施肥实验，这对于从机制上理解生物和地球化学反应是必不可少的。

The Southern Ocean is a critical region for understanding the role of the oceans in global carbon cycling and its potential to regulate climate change. Besides being an area of high influx of atmospheric carbon and deep water formation, the persistently high concentrations of major nutrients in Antarctic circumpolar waters represent the largest pool of unrealized primary production potential in the oceans. This project is part of a larger effort to test the hypothesis that iron availability limits phytoplankton production and biomass accumulation, nutrient utilization and C02drawdown in the Southern Ocean. Drs. Landry, Chisholm and Bidigare, will contribute by investigating the effects of iron enrichment and silicate availability on the species composition and size structure of the plankton community and taxon-specific growth rates and fluorescence responses of the phytoplankton. Functional and taxonomic components of the plankton community from bacteria to mesozooplankton will be quantified by a combination of flow cytometry, taxon-specific pigments, video image-analysis microscopy and optical plankton counting. In addition, they will use dilution and gut fluorescence techniques to determine micro- and mesozooplankton contributions to grazing and to evaluate grazing as an alternate control mechanism preventing significant net growth of some or all of the phytoplankton populations. The research will bring a community perspective to the interpretation of these in situ fertilization experiments which is essential for a mechanistic understanding of the biological and geochemical responses.