Evidence for high iron requirements of colonial Phaeocystis antarctica at low irradiance
Evidence for high iron requirements of colonial Phaeocystis antarctica at low irradiance
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低辐照度条件下南极褐囊藻殖民体高铁需求的证据
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发表时间：
2007
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通讯作者：
G. R. DiTullio
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作者：
P. Sedwick;N. Garcia;S. F. Riseman;C. Marsay;G. R. DiTullio
我们进行了现场和实验室实验，以检查罗斯海南极棕囊藻对铁的需求。 2003 年 12 月，我们在罗斯海冰间湖中进行了铁/光操纵生物测定实验，使用的藻类组合主要是南极褐囊藻，这些藻类是从周围溶解铁浓度约为 0.4 nM 的地表水中收集的。该实验的结果表明，南极洲 P. antarctica 的生长速率在高辐照度（入射表面辐照度的 50%）下得到提高，但不受铁添加的影响，并且辐照度升高导致细胞叶绿素 a 含量显着降低。我们还利用 2003 年 12 月从罗斯海冰间湖采集的单一藻类、非无菌的南极 P. antarctica 菌株和低铁 (<0.2 nM) 过滤海水进行了实验室铁剂量反应生物测定实验。通过使用严格的痕量金属清洁技术，我们在~0°C 下进行了剂量反应铁添加实验，没有使用有机螯合剂来控制溶解铁水平。在本实验相对较低的辐照度下 (∼20 μE m−2 s−1)，估计的硝酸盐特定生长速率作为溶解铁浓度的函数可以通过莫诺关系来描述，产生相对于 0.45 nM 溶解铁生长的半饱和常数。与其他南极浮游植物的估计值相比，该值相对较高。我们的研究结果表明，铁和光可用性的季节性变化在限制罗斯海冰间湖中南极褐囊藻的生长和生物量方面发挥着关键作用。
We have carried out field and laboratory experiments to examine the iron requirements of colonial Phaeocystis antarctica in the Ross Sea. In December 2003, we performed an iron/light-manipulation bioassay experiment in the Ross Sea polynya, using an algal assemblage dominated by colonial Phaeocystis antarctica, collected from surface waters with an ambient dissolved Fe concentration of ∼0.4 nM. Results from this experiment suggest that P. antarctica growth rates were enhanced at high irradiance (∼50% of incident surface irradiance) but were unaffected by iron addition, and that elevated irradiance mediated a significant decrease in cellular chlorophyll a content. We also conducted a laboratory iron dose–response bioassay experiment using a unialgal, non-axenic strain of colonial P. antarctica and low-iron (<0.2 nM) filtered seawater, both collected from the Ross Sea polynya in December 2003. By using rigorous trace-metal clean techniques, we performed this dose–response iron-addition experiment at ∼0°C without using organic chelating reagents to control dissolved iron levels. At the relatively low irradiance of this experiment (∼20 μE m−2 s−1), estimated nitrate-specific growth rate as a function of dissolved iron concentration can be described by a Monod relationship, yielding a half-saturation constant with respect to growth of 0.45 nM dissolved iron. This value is relatively high compared to reported estimates for other Antarctic phytoplankton. Our results suggest that seasonal changes in the availability of both iron and light play critical roles in limiting the growth and biomass of colonial Phaeocystis antarctica in the Ross Sea polynya.