Assessing the impact of global change on the distribution and physicochemical speciation of bioactive trace elements in seawater

必需微量元素的分布和生物有效性可影响海洋生产力、生态系统结构和温室气体的海-气交换。因此，对海洋生物地球化学循环对全球变化的响应的理解必须包括对微量元素来源、汇和化学形态的研究。这是因为海洋微生物对微量元素营养有绝对需求，这有助于解释微生物群落结构的时空变异性，并为海洋中的碳和氮固定设定上限。海洋微生物对微量元素营养的生物有效性不仅受海水中必需元素的浓度控制，还受海水中必需元素的形态或化学形态控制。反过来，微生物可以通过生物介导性的吸收/渗出、氧化还原反应和产生可使水体中的痕量元素溶解的强有机配体来影响微量元素的分布和形态。拟议的研究计划将调查变化的水文和海洋酸化将如何影响海洋表层水域中微量元素营养的生物有效性，并继续研究控制沿海和开阔海洋环境中海洋微生物与痕量金属之间相互作用的主要机制。该方案的长期目标是了解生物活性痕量金属对海洋微生物的分布和有效性的变化如何影响：1)流入和流出表层海洋的碳和氮通量的大小，以及2)向海洋内部下沉的颗粒物通量的元素和同位素组成。

The distribution and bioavailability of essential trace elements can impact marine productivity, ecosystem structure and air-sea exchange of greenhouse 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 for trace element nutrients 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 element nutrients to marine microbes is controlled not only by the concentration but the speciation, or chemical form, that essential elements 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 proposed research program will investigate how changing hydrography and ocean acidification will affect the bioavailability of trace element nutrients in marine surface waters and continue studies of the dominant mechanisms that control interactions between marine microbes and trace metals in coastal and open ocean environments. The long term goals of the program are to provide an understanding of how changes in the distribution and availability of bioactive trace metals to marine microbes affect: 1) the magnitude of C and N fluxes into and out of the surface ocean, and, 2) the elemental and isotopic composition of the sinking flux of particulate matter to the ocean interior.