Collaborative Research: Nitrogen fixation, nutrient supply and biological production in the Gulf of Mexico

本项目将研究在向墨西哥湾温带沿海和近海沃茨供应氮这一基本营养物方面物理、化学和生物因素的相互作用。海湾是一个经济上重要但研究不足的边缘海，拥有主要的商业和娱乐渔业以及广泛的化石燃料矿床。在墨西哥湾的近海和沿海沃茨，固氮（固氮）蓝藻经常大量繁殖，有限的数据表明，它们为浮游食物网提供了大量的氮和碳。这些固氮生物也可能在为其他生物提供氮方面发挥关键作用，包括鱼类毒性赤潮甲藻Karenia brevis。尽管它的重要性，目前很少有人知道的因素，促进N2固定在海湾或不同的物理和生物过程中创造的条件，有利于N限制在水柱的相对重要性。墨西哥湾受河流输入和平流过程的强烈影响，为研究营养动态、生产力的物理强迫、陆地-海洋联系以及土地利用和气候变化对海洋生态系统的潜在影响提供了一个极好的模式系统。墨西哥湾相对较小的盆地提供了一个机会，可以量化和研究物理、化学、以及与广泛的其他沿海和海洋系统有关的生物过程。土地使用和气候变化可能影响墨西哥湾的环流和水文地理，以及河流输入的规模和性质，所有这些都对墨西哥湾的海洋地球化学产生不确定的影响。这项研究将及时深入了解这些过程，并将为评估和预测未来土地使用和气候变化对该系统的影响提供一个了解的基线。该项目将为我们理解调节固氮的因素及其在支持温带沃茨生物群中的作用做出重要贡献。具体工作目标包括：1.确定墨西哥湾的主要固氮生物群，并描述它们在不同区域和水体中的分布和活动。定量分析平流过程、中尺度特征和河流输入对海湾营养盐限制和固氮作用的影响，并评估这些过程对固氮作用的控制作用以及不同区域固氮生物群落时空生态位分化的程度.使用卫星数据和物理模型来扩大我们的测量空间，并评估在墨西哥湾的N2固定的区域意义。研究人员还将使用耦合物理/生物模型来探索物理强迫的变化以及可能的土地利用和气候变化情景在改变墨西哥湾营养动态和N2固定方面的潜在影响。研究人员及其机构对本科和研究生教育有着坚定的承诺。该项目包括对研究生、技术人员和本科生的支持。除了同行评审的论文和网站，针对K-12教师的研讨会，以及一个涉及高中教师研究的项目将被用来在当地社区广泛传播该项目的成果。调查人员致力于增加海洋科学界的多样性，并积极参与其机构的招聘和培训工作。

This project will study the interplay of physical, chemical, and biological factors in supplying nitrogen, an essential nutrient, to temperate coastal and offshore waters of the Gulf of Mexico. The Gulf is an economically important but understudied marginal sea with major commercial and recreational fisheries as well as extensive fossil fuel deposits. Diazotrophic (N2-fixing)) cyanobacteria bloom regularly in offshore and coastal waters of the Gulf and the limited data suggest that they contribute significant quantities of both nitrogen and carbon to the pelagic food web. These diazotrophs may play also a critical role in supplying N to other organisms, including the ichthyotoxic red tide dinoflagellate Karenia brevis. Despite its importance, little is currently known of the factors that promote N2-fixation in the Gulf or the relative significance of different physical and biological processes in creating conditions that favor N limitation in the water column. The Gulf of Mexico is strongly influenced by both riverine inputs and advective processes, providing an excellent model system for studying nutrient dynamics, physical forcing of productivity, terrestrial-oceanic linkages, and the potential impact of land use and climate change on marine ecosystems.The relatively small basin of the Gulf of Mexico provides an opportunity to quantify and study interactions among physical, chemical, and biological processes relevant to a broad range of other coastal and oceanic systems. Land-use and climate change are likely to affect the circulation and hydrography of the Gulf, as well as the magnitude and nature of riverine inputs, all with uncertain impacts on the biogeochemistry of the Gulf of Mexico. This research will provide timely insights into these processes and will generate a baseline of understanding for evaluating and predicting the impact of future land use and climate changes in the system. This project will make an important contribution to our understanding of the factors that regulate N2-fixation and its role in supporting the biota in temperate waters. The following specific goals are included in the work:1. Identify the major diazotroph groups in the Gulf of Mexico and characterize their distribution and activity in different regions and water masses.2. Quantify the impact of advective processes, mesoscale features, and riverine inputs on nutrient limitation and N2-fixation in the Gulf, and evaluate the controls on N2-fixation and the degree of spatial and temporal niche differentiation among diazotroph assemblages in different regions affected by these processes.3. Use satellite data and physical models to scale up our measurements spatially and to evaluate the regional significance of N2-fixation in the Gulf of Mexico. The researchers will also use a coupled physical/biological model to explore variability in the physical forcing and the potential impact of likely land use and climate change scenarios in altering nutrient dynamics and N2-fixation in the Gulf of Mexico.The investigators and their institutions have a strong commitment to undergraduate and graduate education. This project includes support for graduate students, a technician, and undergraduates. In addition to peer-reviewed papers and websites, workshops aimed at K-12 teachers, and a program involving high school teachers in research will be used to disseminate the results of this project broadly in the local community. The investigators are committed to increasing the diversity of the ocean science community and are active in recruiting and training efforts at their institutions.