Iron requirements of the pennate diatom Pseudo-nitzschia: Comparison of oceanic (high-nitrate, low-chlorophyll waters) and coastal species

• Main Authors: Adrian Marchetti, Maria T. Maldonado, Erin S. Lane, Paul J. Harrison
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Pacific; Subarctic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.1686; http://www.aslo.org/lo/toc/vol_51/issue_5/2092.pdf

We quantified and compared physiological parameters and iron requirements of several oceanic Pseudonitzschia spp., newly isolated from the high-nitrate, low-chlorophyll waters of the northeast subarctic Pacific, with coastal Pseudo-nitzschia spp. and the oceanic centric diatom Thalassiosira oceanica at a range of iron concentrations. In iron-replete conditions, the iron (Fe) : carbon (C) ratios in the six Pseudo-nitzschia isolates ranged from 157 mmol Fe mol C 21 to 248 mmol Fe mol C 21, with no apparent differences between oceanic and coastal isolates. In low iron conditions, all Pseudo-nitzschia spp. exhibited marked reductions in photosynthetic efficiency, whereas the extent of the reductions in specific growth rates varied among species. When iron-limited, the Fe: C ratios decreased significantly in all oceanic Pseudo-nitzschia species, with the lowest ratios ranging from 2.8 mmol Fe mol C 21 to 3.7 mmol Fe mol C 21. Combined with faster growth rates, lower Fe: C ratios in oceanic isolates of Pseudo-nitzschia resulted in significantly higher iron-use efficiencies relative to their coastal congeners and T. oceanica. The wide range between iron-replete (Fe-Qhigh) and iron-limited (Fe-Qlow) quotas indicates that oceanic Pseudo-nitzschia spp. have an extensive plasticity in iron contents relative to other diatoms grown at similar iron concentrations reported in the literature; the Fe-Qhigh: Fe-Qlow ratios for oceanic species were 46 to 67, whereas for coastal Pseudo-nitzschia species they were 16 and 43. We suggest that the ability of oceanic