Collaborative Research: Phytoplankton Community Dynamics and Physiological Status in the South Atlantic Subtropical Gyre and Benguela Upwelling Systems

在过去几年中，先进的三维气候模型强调了浮游植物功能群在影响海洋生物地球化学方面的重要性。最近的模型预测，气候变暖将导致低生产力、永久分层的亚热带环流生物群落的扩大，特别是在南半球。因此，必须加强对福建省藻类群落结构、生理状况和生态地球化学的研究。由于其庞大的规模，寡营养环流对全球碳和硫（例如二甲基硫醚; DMS）循环以及全球气候都很重要。然而，影响寡营养环流中二甲硫醚通量的生态和生理过程仍然十分复杂，尚未得到解决。该项目将调查生物硫化合物的现场水平，并评估从贫营养环流到本格拉上升流的生产性沃茨的采样不足的南大西洋带状样带中的藻类群落结构和生理状况。由于南大西洋的风成铁通量较低，该地区被认为受到铁和常量营养素的共同限制。但是，很少有研究直接调查了该地区的原位生理状态和藻类群落结构，特别是关于铁和常量营养素的共同限制。研究人员将进行几个诊断性营养富集实验，以评估藻类类特定的生物地球化学反应。他们将利用一个国家的最先进的，远洋，高速，细胞分选流式细胞仪，以确定藻类类特定浓度的生物硫化合物，并估计C/叶绿素比从原位种群和诊断营养富集实验。了解特定藻类类别的DMSP：叶绿素比率对于提高预测模型的准确性以确定大气中的DMS通量非常重要。此外，研究人员将使用铁胁迫的分子和生化指标（黄素氧还蛋白）评估原位藻类种群的生理状态。基于荧光的方法将用于估计藻类类特定的光合效率，初级生产和光合作用与辐照参数的瞬时测量。这些测量对于遥感算法估计初级生产力和气候建模者确定和预测海洋对气候变暖的生物地球化学反应至关重要。南大西洋的浮游植物群落结构和生理学特征尚不明确，但对全球海洋地球化学模型很重要。这项研究将提供定量的经验结果，建模人员可以利用在构建强大的，机械精确的数值模型，这一重要领域。此外，确定铁的生理状态和藻类群落组成的本格拉上升流区将提供重要的见解，这一高生产力的地区。该项目还将在多个层面做出重大的教育贡献，包括计划中的研究生和本科生、博士后研究员的研究参与以及社区宣传和教育活动。

In the past few years, sophisticated three-dimensional climate models have emphasized the importance of phytoplankton functional groups in affecting the biogeochemistry of the oceans. Recent models have predicted that climate warming will lead to expansion of the low productivity, permanently stratified subtropical gyre biome, especially in the southern hemisphere. As a result, it is imperative to increase our understanding of algal community structure, physiological status and biogeochemistry in this province. Due to their sheer size, oligotrophic gyres are important to the global carbon and sulfur (e.g. dimethylsulfide; DMS) cycles and as a result to global climate. Ecological and physiological processes that affect DMS fluxes in oligotrophic gyres, however, remain complex and unresolved. This project will investigate the in-situ levels of biogenic sulfur compounds and assess algal community structure and physiological status in a zonal transect of the undersampled South Atlantic Ocean from the oligotrophic gyre to the productive waters of the Benguela upwelling. Due to low aeolian iron fluxes to the South Atlantic Ocean, the region is believed to be co-limited by iron and macronutrients. But there have been very few studies that have directly investigated the in-situ physiological status and algal community structure in this region, especially with respect to co-limiting iron and macronutrients. The investigators will perform several diagnostic nutrient enrichment experiments to assess algal class-specific biogeochemical responses. They will utilize a state-of-the-art, ocean-going, high speed, cell-sorting flow cytometer to determine algal class specific concentrations of biogenic sulfur compounds, and to estimate C/Chl ratios from in-situ populations and from diagnostic nutrient enrichment experiments. Knowledge of algal class-specific DMSP:Chl ratios is important in improving the accuracy of predictive models to determine the DMS flux to the atmosphere. In addition, the investigators will assess the physiological status of in-situ algal populations using molecular and biochemical indicators (flavodoxin) of iron stress. A fluorescence based approach will be used to estimate algal class-specific photosyntheic efficiency, primary production and instantaneous measurements of photosynthesis vs. irradiance parameters. These measurements will be vital to remote sensing algorithms for estimating primary production and to climate modelers for determining and predicting the oceans biogeochemical response to climate warming Broader Impacts. Phytoplankton community structure and physiology in the South Atlantic Ocean is not well characterized but is important with respect to global biogeochemical models. This research will provide quantitative empirical results that modelers can utilize in constructing robust, mechanistically-accurate numerical models of this important region. In addition, determining the iron physiological status and algal community composition of the Benguela upwelling region will provide important insights into this high productivity region. This project will also make significant educational contributions at several levels, including the planned research involvement of graduate and undergraduate students, postdoctoral associates, and community outreach and educational activities.