In-Situ Determination of Iron Limitation in the Peruvian Upwelling System

中尺度铁施肥试验存在一定的争议，其成本过高，在许多开阔的海洋环境中难以进行，也不适合进行精细尺度的海洋生态研究。铁限制的原位诊断指标可以避免上述问题。研究人员将与痕量金属化学家和生物学家合作，探索利用原位生化和生物物理指标来评估其实用性和有效性的适用性。在这样做的过程中，科学家们还将参与调查秘鲁沿海上升流系统是铁有限的假设。将研究的两种原位指标包括：(1)使用快速重复率荧光仪测量光化学效率；(2)定量测量（使用高效液相色谱和毛细管电泳相结合的方法）藻类中铁氧还蛋白和黄氧还蛋白浓度，作为铁营养状况的指标。这两种方法将为宏观营养丰富的秘鲁上升流区藻类铁限制提供补充证据。此外，将使用14C色素标记来测量藻类的分类群特异性生长速率，以帮助解释和支持其他研究人员对环境铁浓度的测量，以及铁添加实验的结果，这些实验将同时在秘鲁上升流地区的一个样带上进行。

Mesoscale iron fertilization experiments are somewhat controversial, prohibitively expensive, logistically difficult to perform in many open ocean environments and not suitable for fine scale ecological ocean studies. In situ diagnostic indicators of iron limitation can circumvent the above stated problems. The investigators will collaborate with trace metal chemists and biologists to explore the applicability of utilizing in situ biochemical and biophysical indicators to assess their usefulness and validity. In so doing, the scientists will also participate in investigating the hypothesis that the Peru coastal upwelling system is iron-limited. The two in situ indicators that will be investigated include (1) photochemical efficiency measurements using a fast repetition rate fluorometer and (2) quantitative measurements (using a combined high performance liquid chromatography and capillary electrophoresis method) of ferredoxin and flavodoxin concentrations in algae as an indicator of iron-nutritional status. These two methods will provide complimentary evidence regarding algal iron-limitation in the macro-nutrient replete Peru upwelling region. In addition, taxon-specific growth rates of algae will be measured using 14C pigment labeling to help interpret and support measurements by other investigators of the ambient iron concentration as well as the results from iron-addition experiments that will be run concomitantly on a transect across the Peru upwelling region.