Particulate trace metal dynamics in response to increased CO2 and iron availability in a coastal mesocosm experiment
Particulate trace metal dynamics in response to increased CO2 and iron availability in a coastal mesocosm experiment
复制标题
沿海中生态实验中二氧化碳和铁可用性增加的颗粒痕量金属动力学响应
作者：
M. R. Lorenzo;M. Segovia;J. Cullen;M. T. Maldonado
抽象的。大气中二氧化碳浓度的上升正在导致海洋酸化，并将影响海洋过程和微量金属生物地球化学。 2012 年 6 月，我们在 Raunefjord（挪威卑尔根）进行了一项中生态实验，包括对环境和升高的 pCO2 进行完全析因设计和/或添加铁载体去铁胺 B (DFB)。此外，还控制常量营养素浓度以促进球石藻赫胥黎的开花。我们报告了本实验期间颗粒痕量金属浓度的变化。我们的研究结果表明，颗粒状 Ti 和 Fe 以成岩物质为主，而颗粒状 Cu、Co、Mn、Zn、Mo 和 Cd 则具有较强的生物成分。此外，海水中 Cu、Co、Zn、Cd、Mn、Mo 和 P 的颗粒浓度与浮游植物生物量 (μgC L−1) 之间存在显着相关性，支持水华对这些颗粒元素分布的显着影响。 E. huxleyi 水华中这些生物金属的浓度排序如下：Zn < Cu ≈ Mn < Mo < Co < Cd。 CO2 的变化影响总颗粒物浓度和某些金属的生物金属比率 (Me : P)，而 DFB 的添加仅显着影响某些颗粒金属的浓度 (mol L−1)。 CO2 的变化对颗粒铁浓度的影响最为明显和显着，在高 CO2 条件下其浓度降低。事实上，高 CO2 和/或 DFB 促进了颗粒铁的溶解，而铁载体的存在有助于维持高溶解铁。在 DFB 存在的情况下，颗粒铁浓度和溶解铁浓度之间的这种变化，促进了环境二氧化碳处理中赫胥氏艾球藻的大量繁殖。此外，高CO2降低了Co、Zn和Mn的Me : P比率，同时增加了Cu : P比率。这些发现支持了理论预测，即海水溶解形态由自由离子（例如 Co、Zn 和 Mn）主导的金属的金属与磷的摩尔比（Me : P 比率）在海洋酸化下可能会降低或保持恒定。相比之下，高二氧化碳预计会改变与碳酸盐（例如铜）相关的溶解金属的形态，增加其生物利用度并导致更高的 Me : P 比率。
Abstract. Rising concentrations of atmospheric carbon dioxide are causing ocean acidification and will influence marine processes and trace metal biogeochemistry. In June 2012, in the Raunefjord (Bergen, Norway), we performed a mesocosm experiment, comprised of a fully factorial design of ambient and elevated pCO2 and/or an addition of the siderophore desferrioxamine B (DFB). In addition, the macronutrient concentrations were manipulated to enhance a bloom of the coccolithophore Emiliania huxleyi. We report the changes in particulate trace metal concentrations during this experiment. Our results show that particulate Ti and Fe were dominated by lithogenic material, while particulate Cu, Co, Mn, Zn, Mo and Cd had a strong biogenic component. Furthermore, significant correlations were found between particulate concentrations of Cu, Co, Zn, Cd, Mn, Mo and P in seawater and phytoplankton biomass (µgC L−1), supporting a significant influence of the bloom in the distribution of these particulate elements. The concentrations of these biogenic metals in the E. huxleyi bloom were ranked as follows: Zn < Cu ≈ Mn < Mo < Co < Cd. Changes in CO2 affected total particulate concentrations and biogenic metal ratios (Me : P) for some metals, while the addition of DFB only significantly affected the concentrations of some particulate metals (mol L−1). Variations in CO2 had the most clear and significant effect on particulate Fe concentrations, decreasing its concentration under high CO2. Indeed, high CO2 and/or DFB promoted the dissolution of particulate Fe, and the presence of this siderophore helped in maintaining high dissolved Fe. This shift between particulate and dissolved Fe concentrations in the presence of DFB, promoted a massive bloom of E. huxleyi in the treatments with ambient CO2. Furthermore, high CO2 decreased the Me : P ratios of Co, Zn and Mn while increasing the Cu : P ratios. These findings support theoretical predictions that the molar ratios of metal to phosphorous (Me : P ratios) of metals whose seawater dissolved speciation is dominated by free ions (e.g., Co, Zn and Mn) will likely decrease or stay constant under ocean acidification. In contrast, high CO2 is predicted to shift the speciation of dissolved metals associated with carbonates such as Cu, increasing their bioavailability and resulting in higher Me : P ratios.