Collaborative Research: Southern Ocean Iron Experiment (SOFeX): Mesoscale Iron Fertilization Effects on Plankton Community Structure, 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的潜力的关键区域。南极环极沃茨除了是大气碳大量流入和深水形成的地区外，主要营养物的持续高浓度是海洋中未实现的初级生产潜力的最大池。该项目是一个更大的努力，以测试假设，铁的可用性限制浮游植物的生产和生物量积累，营养利用和CO2下降在南大洋的一部分。 Landry、奇泽姆和Bidigare博士将通过调查铁富集和硅酸盐可用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分类特异性生长速率和荧光反应的影响作出贡献。浮游生物群落的功能和分类组成部分，从细菌到中型浮游动物，将通过流式细胞术，分类特定的色素，视频图像分析显微镜和光学浮游生物计数相结合的量化。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。这项研究将带来一个社区的角度来解释这些原位施肥实验，这是必不可少的生物和地球化学反应的机械理解。

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.