BIOCOMPLEXITY: Collaborative Research: Factors Affecting, and Impact of, Diazotraphic Microorganisms in the Western Equatorial Atlantic

生物复杂性：合作研究：西赤道大西洋固氮微生物的影响因素和影响

• 批准号: 9912333
• 负责人: Sergio Sanudo-Wilhelmy
• 金额: $ 33.5万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-01-01 至 2004-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9912333&HistoricalAwards=false
• 关键词: BIOCOMPLEXITY; Collaborative; Research; Factors; Affecting

BIOCOMPLEXITY: Collaborative Research: Factors affecting, and impact of,diazotrophic microorganisms in the western Equatorial Atlantic Ocean This biocomplexity research focuses on plankton dynamics in the western Equatorial Atlantic Ocean (WEQAT). This is a complex and understudied ecosystem that has significant impacts on marine resourcesin the region as well as in downstream areas such as the Caribbean Sea. The study centers ondiazotrophic (nitrogen fixing) microorganisms as keystone species. Geological, physical, biological,chemical and even social factors all have a major influence on population biology and activity ofdiazotrophs in the WEQAT. Diazotrophs in turn have a major impact on other phytoplankton andtrophic levels through input of fixed nitrogen (N). The Amazon River affects the regionphysically by changing salinity and thereby water column stratification, and geochemically byintroducing iron and silicate which can then biologically stimulate the growth of diatoms thatcontain the N2 fixing endosymbiont Richelia intracellularis. Furthermore, the area receivessignificant seasonal atmospheric inputs of iron in dust from the Sahel region of Africa, which canpromote the growth of the important N2 fixing cyanobacterium Trichodesmium. Thisatmospheric iron source is directly deposited on the surface waters where biological activity isgreatest. For Trichodesmium, the physical environment (e.g. high wind speed) can also inhibitactivity and the formation of blooms. Diazotrophs may be affected by land use practices in theAmazon Basin and the African Sahel, and N2 fixed by marine plankton can affect humans bystimulating primary productivity and fishery yields. Using both remote sensing and shipboard measurements, scientists will examine the complex processes which structure these planktonic diazotroph populations, influence their importance in CO2 andN2 fixation, which, in turn, affect other planktonic processes. The seasonal and spatialrelationships of Trichodesmium and Hemiaulus / Richelia associations will be examined withdirect reference to the major routes of inputs of Fe and Si, and with regard to the physicalenvironment. The group of collaborating scientists will examine the trophic structures associated with each diazotrophic community, including the vertical distribution of processes and associated autotrophic andheterotrophic plankton populations. These data will be used to develop and verifybiogeochemical and trophodynamic models that incorporate the complex physical, chemical andbiological interactions that characterize the WEQAT region. The models will, in turn, be used toexamine the hypothesis that physical forcing, through its effect on the diazotrophic populationsand the structure of the food web, influences N2 fixation and, in part, determines the highproductivity of the WEQAT. The work uses a combination of both observations and models to address threefundamental issues in biocomplexity: 1) the relationship between ecosystem structure andfunction in a system that is both nonlinear and high-dimensional; 2) the response of a nonlinearecosystem to environmental forcing; and 3) the relevant level of detail, including the resolutionof physical space, that must be incorporated in nonlinear systems to capture the dynamics of aglobal ecosystem property (here, high productivity). The research will significantly advance our understanding of the interaction between physical and biogeochemical processes in an important area the world's oceans, and identify how these interactions regulate variability in marine ecosystem productivity.

生物复杂性：合作研究：影响西赤道大西洋重氮营养微生物的因素和影响这项生物复杂性研究侧重于西赤道大西洋（WEQAT）的浮游生物动态。这是一个复杂且研究不足的生态系统，对该地区以及加勒比海等下游地区的海洋资源产生了重大影响。该研究将固氮微生物作为关键物种。地质、物理、生物、化学甚至社会因素都对WEQAT重氮营养菌的种群生物学和活性有重要影响。重氮营养体反过来又通过输入固定氮(N)对其他浮游植物和营养水平产生重大影响。亚马逊河通过改变盐度和水柱分层来影响区域物理，通过引入铁和硅酸盐来影响地球化学，这些铁和硅酸盐可以在生物上刺激硅藻的生长，硅藻含有固定氮的内共生菌胞内黎切菌。此外，该地区从非洲萨赫勒地区的沙尘中获得了大量的季节性大气铁输入，这可以促进重要的固氮蓝藻Trichodesmium的生长。这种大气铁源直接沉积在生物活性最强的地表水上。对于木霉而言，物理环境（如高风速）也可以抑制其活性和华花的形成。在亚马逊盆地和非洲萨赫勒地区，重氮营养体可能受到土地利用方式的影响，海洋浮游生物固定的氮可以通过刺激初级生产力和渔业产量来影响人类。利用遥感和船载测量，科学家们将研究构成这些重氮营养浮游生物种群的复杂过程，影响它们在二氧化碳和氮气固定中的重要性，而二氧化碳和氮气固定反过来又影响其他浮游生物过程。将直接参考铁和硅的主要输入途径以及物理环境来研究trichodesium和Hemiaulus / Richelia关联的季节和空间关系。合作科学家小组将研究与每个重氮营养群落相关的营养结构，包括过程的垂直分布以及相关的自养和异养浮游生物种群。这些数据将用于开发和验证生物地球化学和滋养动力学模型，这些模型包含了WEQAT地区特征的复杂物理、化学和生物相互作用。反过来，这些模型将被用来检验这样一种假设，即物理强迫，通过其对重氮营养种群和食物网结构的影响，影响氮的固定，并在一定程度上决定了WEQAT的高生产率。这项工作结合了观察和模型来解决生物复杂性中的三个基本问题：1)非线性和高维系统中生态系统结构和功能之间的关系；2)非线性生态系统对环境强迫的响应；3)相关的细节水平，包括物理空间的分辨率，必须纳入非线性系统以捕捉全球生态系统属性的动态（这里是高生产力）。该研究将极大地促进我们对世界海洋重要地区物理和生物地球化学过程之间相互作用的理解，并确定这些相互作用如何调节海洋生态系统生产力的变化。