Nickel utilization in phytoplankton assemblages from contrasting oceanic regimes
Nickel utilization in phytoplankton assemblages from contrasting oceanic regimes
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DOI：
10.1016/j.dsr.2009.12.014
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发表时间：
2010-04-01
影响因子：
2.4
通讯作者：
Barbeau, Katherine
中科院分区：
文献类型：
--
作者：
Dupont, Christopher L.;Buck, Kristen N.;Barbeau, Katherine
在大多数海洋环境中，溶解的镍（Ni）浓度在地表水中随着深度浓度的增加而下降，这意味着生物学在镍的地球化学分布中起着重要作用。对海洋表面浮游植物分离物的研究已经确立了Ni在尿素同化和氧化防御中的生化作用。采用瓶底施肥试验，考察低水平添加镍的效果。在秘鲁和加利福尼亚近海的几个地点以及加利福尼亚湾的地表水中，尿素和Ni+尿素的添加相对于对照和+Ni处理持续促进了浮游植物的生长，除了沿海上升流地点和秘鲁水域。在上升流部位没有观察到任何影响，但在秘鲁水域，尿素添加导致浮游植物色素增加，磷酸盐减少，只有在同时添加Ni时，这表明了生物化学依赖的Ni-尿素共拟。在加利福尼亚湾，不添加尿素的Ni添加导致蓝藻、微真核生物和相应色素的丰度增加，尿素添加表明整个浮游植物群落也是尿素有限的。蓝藻和潜在的微真核生物似乎以生物化学独立的方式受到Ni和尿素的限制。同时，采用基于放射性示踪剂的吸收实验研究了生物镍同化的动力学和空间变异。在这些实验中，添加的放射性示踪剂很少与存在的天然Ni平衡，从而排除了对原位Ni吸收率的估计，并表明大部分天然Ni不是生物可利用的。缺乏平衡可能并不妨碍群落Ni摄取动力学的测量，也不妨碍不同地点之间测量速率的比较。在分层氮耗尽群落中观察到最高的VmaxKp-1值，反映了低浓度下Ni获取的竞争优势，可能以与Ni的生化利用一致的方式将Ni和氮的生物地球化学联系起来。总体而言，在富营养化带群落中，吸收速率高于非富营养化带群落，直接与Ni的营养样深度剖面相吻合。在硝酸盐富营养化贫铁秘鲁站观察到的Ni吸收速率比其他站点低一个数量级。这一结果与计算结果一致，表明细胞表面饱和的Ni和铁（Fe）转运体可能会限制低铁水域的吸收速率。(C) 2010 Elsevier Ltd.版权所有
In most oceanic environments, dissolved nickel (Ni) concentrations are drawn clown in surface waters with increasing concentrations at depth, implying a role for biology in the geochemical distribution of Ni Studies with phytoplankton isolates from the surface ocean have established the biochemical roles of Ni in the assimilation of urea and oxidative defense To determine if these requirements are relevant in natural marine planktonic assemblages, bottle-based fertilization experiments were used to test the effects of low-level additions of Ni. urea, or both Ni and urea to surface waters at several locations offshore of Peru and California, as well as in the Gulf of California Urea and Ni+ urea additions consistently promoted phytoplankton growth relative to control and +Ni treatments, except in a coastal upwelling site and Peruvian water. No effect was observed in the upwelling site, but in Peruvian waters urea additions resulted in increased phytoplankton pigments and phosphate drawdown only when Ni was added concurrently, suggesting a biochemically dependent Ni-urea colimitation In the Gulf of California, Ni additions without urea resulted in increased abundances of cyanobacteria, picoeukaryotes, and the corresponding pigments As urea additions showed the overall phytoplankton community was also urea-limited, it appears that the cyanobactena and potentially the picoeukaryotes were colimited by Ni and urea in a biochemically independent fashion. In parallel, radiotracer-based uptake experiments were used to study the kinetics and spatial variation of biological Ni assimilation. In these experiments, the added radiotracer rarely equilibrated with the natural Ni present, precluding estimates a determination of in situ Ni uptake rates and suggesting that much of the natural Ni was not bioavailable. The lack of equilibration likely did not preclude the measurement of community Ni uptake kinetics, nor the comparison of measured rates between locations The highest VmaxKp-1 values, which reflect a competitive advantage in Ni acquisition at low concentrations, were observed in stratified nitrogen-deplete communities, potentially linking Ni and nitrogen biogeochemistry in a manner consistent with the biochemical utilization of Ni. Overall, uptake rates were higher in the euphotic rather than non-euphotic zone communities, directly reconciling the nutrient-like depth profile of Ni The Ni uptake rates observed at the nitrate-replete Fe-deplete Peru stations were an order of magnitude lower than the other sites This result agrees with calculations suggesting that saturation of the cell surface with Ni and iron (Fe) transporters may limit uptake rates in low Fe waters. (C) 2010 Elsevier Ltd. All rights reserved