Determining the distribution and physicochemical speciation of bioactive trace elements in the oceans under a changing climate

确定气候变化下海洋中生物活性微量元素的分布和理化形态

• 批准号: RGPIN-2014-06170
• 负责人: Cullen, Jay
• 金额: $ 2.33万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=588852
• 关键词: Determining; distribution; physicochemical; speciation; bioactive

The distribution and bioavailability of essential (e.g. Cu, Fe and Zn) and potentially toxic (e.g. Cu, Ag and Cd) trace elements in the ocean can impact marine productivity, ecosystem structure and therefore the air-sea exchange of climate active gases. An understanding of the response of marine biogeochemical cycles to global change must, therefore, include studies of trace element sources, sinks, and chemical speciation. This is because marine microbes have absolute requirements or sensitivities to trace element nutrients and toxins that can help explain temporal-spatial variability in microbial community structure and set upper limits on carbon and nitrogen fixation in the sea. The bioavailability of trace elements to marine microbes is controlled not only by the concentration but the speciation, or chemical form, that metals take in seawater. In turn, microorganisms can affect the distribution and speciation of trace elements through biologically mediated uptake/exudation, redox reactions and the production of strong organic ligands that complex dissolved trace elements in the water column. The long-term goals of my research program are to understand the processes that control the distribution, chemical speciation and resulting bioavailability of trace metals, and how altered physical and chemical conditions in response to climate change are likely to impact the biogeochemical cycling of metals in the ocean. Recently, my research group has made significant progress towards these goals through the development and application of powerful analytical methods in both the field and the laboratory. We have focused on metals that control primary production and community structure (e.g. Fe, Cu and Zn), serve as paleoceanographic tracers that provide important information regarding the oceans role in past climate change (e.g. Cd, Ag), or potentially toxic heavy metals that might negatively impact ecosystem health and function (Cu, Ag and Cd). Over the next 5 years my research objectives are to: 1) examine how changing temperature, pH and light regimes in high latitude ocean surface waters will impact the cycling of biologically important metals; 2) unravel how trace metal fluxes are modified at the ocean margins with an emphasis on sources and sinks at the continental shelves; and 3) determine how the secular trend of decreasing oxygen levels in the ocean will impact the relative distribution of bioactive metals. The work proposed here will help to elucidate the role that trace metals play in shaping community composition and productivity of marine microbes that represent the base of the ocean food chain. Metals can act as essential nutrients and toxins that can modulate the biological production and consumption of climate active gases. Our data will allow for better parameterization of biogeochemical rate processes in coupled atmosphere-ocean models designed to predict the response of marine systems in the subarctic and Arctic to regional warming, ocean acidification, and changing sea ice and light regimes. In addition, a more thorough understanding of what controls the basin scale distribution of trace metals and their relationships with the major algal nutrients will aide in efforts to verify existing and develop new paleoproxies that are essential for reconstructing the oceans role in past climate variability.

海洋中必需的（如铜、铁和锌）和潜在有毒的（如铜、银和镉）微量元素的分布和生物可利用性可影响海洋生产力、生态系统结构，从而影响气候活性气体的海气交换。因此，要了解海洋生物地球化学循环对全球变化的响应，就必须研究微量元素的源、汇和化学形态。这是因为海洋微生物对微量元素营养素和毒素具有绝对需求或敏感性，这有助于解释微生物群落结构的时空变异性，并设定海洋中碳和氮固定的上限。微量元素对海洋微生物的生物利用度不仅取决于浓度，还取决于金属在海水中的形态或化学形式。反过来，微生物可以通过生物介导的吸收/渗出、氧化还原反应和产生强有机配体来影响微量元素的分布和形态，所述强有机配体络合水柱中溶解的微量元素。 我的研究计划的长期目标是了解控制微量金属的分布，化学形态和生物利用度的过程，以及如何改变响应气候变化的物理和化学条件可能会影响海洋中金属的地球化学循环。最近，我的研究小组通过在现场和实验室开发和应用强大的分析方法，在实现这些目标方面取得了重大进展。 我们专注于控制初级生产和群落结构的金属（例如Fe，Cu和Zn），作为古海洋示踪剂，提供有关海洋在过去气候变化中的作用的重要信息（例如Cd，Ag），或可能对生态系统健康和功能产生负面影响的潜在有毒重金属（Cu，Ag和Cd）。在接下来的5年里，我的研究目标是：1）研究高纬度海洋表面沃茨水域的温度、pH值和光照状况的变化将如何影响生物重要金属的循环; 2）揭示微量金属通量如何在海洋边缘发生变化，重点是大陆架的源和汇;以及3）确定海洋中氧气水平下降的长期趋势将如何影响生物活性金属的相对分布。 这里提出的工作将有助于阐明微量金属在塑造代表海洋食物链基础的海洋微生物的群落组成和生产力方面发挥的作用。金属可以作为基本营养素和毒素，调节生物生产和气候活性气体的消耗。我们的数据将允许更好地参数化耦合大气-海洋模型中的地球化学速率过程，该模型旨在预测亚北极和北极海洋系统对区域变暖，海洋酸化以及海冰和光照制度变化的响应。此外，更深入地了解是什么控制了微量金属的流域规模分布及其与主要藻类营养物的关系，将有助于努力核实现有的和开发新的古代用品，这对重建海洋在过去气候变化中的作用至关重要。