The evolution and termination of an iron-induced mesoscale bloom in the northeast subarctic Pacific
The evolution and termination of an iron-induced mesoscale bloom in the northeast subarctic Pacific
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DOI：
10.4319/lo.2005.50.6.1872
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发表时间：
2005-11-01
影响因子：
4.5
通讯作者：
Ramaiah, N
中科院分区：
文献类型：
--
作者：
Boyd, PW;Strzepek, R;Ramaiah, N
我们发起并绘制了硅藻水华在东北亚北极太平洋同时加入溶解铁和示踪剂六氟化硫的中尺度补丁的高硝酸盐，低叶绿素沃茨。水华以羽纹硅藻为主，监测时间为25 d，足以观察水华的演变和终止以及大部分衰退期。快速重复率荧光法表明，硅藻铁充满，直到第12天，随后由4-5-D过渡到铁限制。这一过渡时期的特点是相对较高的藻类生长和营养吸收率，这表明硅藻使用胞内储存的铁。到第16-17天，水华可能同时受到铁和草酸供应的限制，因为低草酸浓度是明显的。建模模拟，使用我们的研究数据，提供了一个估计的临界阈值藻类聚集。在水华期间观察到的硅藻丰度超过了这一阈值之间的第13和17天。在第21天，在50英寸深的表面系留的自由漂流沉积物捕集器中记录了硅藻和硅藻聚集体的大量沉积。虽然水华的终止可能是由铁和草酸的可用性控制，我们不能排除藻类聚集的作用。水华的减少很可能是由大量沉积的开始引发的。在我们的研究中，硅藻物种演替和物种特异性聚集的证据都指向藻类营养胁迫和藻类聚集的启动之间的重要联系。
We initiated and mapped a diatom bloom in the northeast subarctic Pacific by concurrently adding dissolved iron and the tracer sulfur hexafluoride to a mesoscale patch of high-nitrate, low-chlorophyll waters. The bloom was dominated by pennate diatoms and was monitored for 25 d, which was sufficiently long to observe the evolution and termination of the bloom and most of the decline phase. Fast repetition-rate fluorometry indicated that the diatoms were iron-replete until day 12, followed by a 4-5-d transition to iron limitation. This transition period was characterized by relatively high rates of algal growth and nutrient uptake, which pointed to diatoms using intracellularly stored iron. By days 16-17, the bloom was probably limited simultaneously by both iron and silicic acid Supply, because low silicic acid concentrations were evident. Modeling Simulations, using data from our study, provided an estimate of the critical threshold for algal aggregation. Observed diatom abundances during the bloom exceeded this threshold between days 13 and 17. Mass sedimentation of diatorns and diatom aggregates was recorded in surface-tethered free-drifting sediment traps at 50 in in depth on day 21. Although the termination of the bloom was probably controlled by the availability of both iron and silicic acid, we cannot rule out the role of algal aggregation. The bloom decline was likely triggered by the onset of mass sedimentation. During our study, evidence of both diatom species succession and species-specific aggregation point to important links between algal nutrient stress and the initiation of algal aggregation.