Fe availability drives phytoplankton photosynthesis rates during spring bloom in the Amundsen Sea Polynya, Antarctica
Fe availability drives phytoplankton photosynthesis rates during spring bloom in the Amundsen Sea Polynya, Antarctica
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DOI：
10.12952/journal.elementa.000043
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发表时间：
2015-04-08
影响因子：
3.9
通讯作者：
Arrigo, Kevin R.
中科院分区：
文献类型：
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作者：
Alderkamp, Anne-Carlijn;van Dijken, Gert L.;Arrigo, Kevin R.
为了评估南极阿蒙森海洋水华(ASP)春季水华期间浮游植物光合作用速率的驱动因素，我们研究了南极洲棕囊藻(Haptophyceae)水华期间浮游植物的生物量、光合作用速率和水柱生产力，并在甲板培养箱中进行了生物测定实验，测试了铁(Fe)和光照对这些参数的影响。浮游植物生物量和生产力最高(20mug叶绿素a L-1和6.5gCm(-2)d(-1))，在ASP中部，海冰融化和地表变暖增强了层结，减少了混合层深度，增加了光能利用率。相反，最大光合作用速率(P*(Max))、光合作用-光照曲线的初始光限斜率(a*)和光系统II的最大光化学效率(F-v/F-m)在靠近Dotson和Getz冰架潜在铁源的南部ASP最高。在中央ASP，P*(Max)、a*和F-v/F-m均较低。在12个培养中的3个中，Fe的添加提高了浮游植物的生长速度，并且当所有实验被综合分析时达到显著水平，这表明在春季水华形成期间，Fe的有效性可能限制了ASP的几个区域的浮游植物的生长。此外，在几乎所有的实验中，与未修改的对照相比，添加铁增加了P*(Max)、a*和F-v/F-m。与弱光培养相比，强光培养也增加了P*(Max)，但降低了F-v/F-m和a*。这些结果表明，与靠近冰架的区域相比，ASP中部的P*(Max)、a*和F-v/F-m值较低，这是由于铁的有效性较低而不是光的有效性较低。我们的研究表明，更高的铁可利用性(例如，来自更高的冰架融化速度)将提高中央ASP的光合作用速率，并潜在地将水柱生产力提高1.7倍，使ASP比现在更具生产力。
To evaluate what drives phytoplankton photosynthesis rates in the Amundsen Sea Polynya (ASP), Antarctica, during the spring bloom, we studied phytoplankton biomass, photosynthesis rates, and water column productivity during a bloom of Phaeocystis antarctica (Haptophyceae) and tested effects of iron (Fe) and light availability on these parameters in bioassay experiments in deck incubators. Phytoplankton biomass and productivity were highest (20 mu g chlorophyll a L-1 and 6.5 g C m(-2) d(-1)) in the central ASP where sea ice melt water and surface warming enhanced stratification, reducing mixed layer depth and increasing light availability. In -contrast, maximum photosynthesis rate (P*(max)), initial light-limited slope of the photosynthesis-irradiance curve (a*), and maximum photochemical efficiency of photosystem II (F-v / F-m) were highest in the southern ASP near the potential Fe sources of the Dotson and Getz ice shelves. In the central ASP, P*(max), a*, and F-v / F-m were all lower. Fe addition increased phytoplankton growth rates in three of twelve incubations, and at a significant level when all experiments were analyzed together, indicating Fe availability may be rate-limiting for phytoplankton growth in several regions of the ASP early in the season during build-up of the spring bloom. Moreover, Fe addition increased P*(max), a*, and F-v / F-m in almost all experiments when compared to unamended controls. Incubation under high light also increased P*(max), but decreased F-v / F-m and a* when compared to low light incubation. These results indicate that the lower values for P*(max), a*, and F-v / F-m in the central ASP, compared to regions close to the ice shelves, are constrained by lower Fe availability rather than light availability. Our study suggests that higher Fe availability (e.g., from higher melt rates of ice shelves) would increase photosynthesis rates in the central ASP and potentially increase water column productivity 1.7-fold, making the ASP even more productive than it is today.