Confirmation of iron limitation of phytoplankton photosynthesis in the equatorial Pacific Ocean
Confirmation of iron limitation of phytoplankton photosynthesis in the equatorial Pacific Ocean
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DOI：
10.1038/383508a0
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发表时间：
1996-10-10
期刊：
影响因子：
64.8
通讯作者：
Falkowski, PG
中科院分区：
文献类型：
--
作者：
Behrenfeld, MJ;Bale, AJ;Falkowski, PG
赤道东太平洋是仅有的三个开放海洋区域之一，尽管常年硝酸盐和磷酸盐营养浓度很高，但浮游植物叶绿素生物量仍然很低。1993年，在该区域内的一个区域人工富集了单一剂量的可溶性铁，以测试浮游植物是否在生理上被低天然铁浓度阻止利用可用的营养物质（2，3）。虽然光合作用得到了刺激（4），但观察到的水华的缺乏或营养物质浓度的显著下降不能明确归因于浮游动物的摄食（5-7）、进一步的铁限制或次生营养物质限制（2，4）。1995年，进行了第二次铁富集实验（IronEx II），其中添加了相同的铁总剂量，但超过8天（8）。大量浮游植物大量繁殖，显著降低了地表水的养分和二氧化碳浓度（8-10）。在这里，我们报告在IronEx II期间的荧光原位测量，该架子铁富集引发浮游植物的光合装置的生物物理改变，导致在整个实验中增加光合能力，因此，观察到的水华。这些结果明确地建立了浮游植物的生理限制铁的高硝酸盐，低叶绿素的现象，在这个海洋区域的原因。
THE eastern equatorial Pacific Ocean is one of only three open-ocean regions where low phytoplankton chlorophyll biomass persists despite perennially high nitrate and phosphate nutrient concentrations'. In 1993, an area within this region was artificially enriched with a single dose of soluble iron to test whether phytoplankton are physiologically prevented from utilizing the available nutrients by the low natural iron concentrations(2,3). Although photosynthesis was stimulated(4), the observed lack of a bloom or a significant decrease in nutrient concentrations could not he attributed unequivocally to zooplankton grazing(5-7), further iron limitation or secondary nutrient limitation(2,4). In 1995, a second iron-enrichment experiment (IronEx II) was conducted in which the same total dosage of iron was added, but over eight days(8). A massive phytoplankton bloom developed, significantly reducing surface-water nutrient and CO2 concentrations(8-10). Here we report in situ measurements of fluorescence during IronEx II, which shelf that the iron enrichment triggered biophysical alterations of the the phytoplankton's photosynthetic apparatus, resulting in increased photosynthetic capacities throughout the experiment and, hence, the observed bloom. These results unequivocally establish physiological limitation of phytoplankton by iron as the cause of the high-nitrate, low-chlorophyll phenomenon in this ocean region.