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The elemental stoichiometry and composition of an iron‐limited diatom
Author(s) -
Price Neil M.
Publication year - 2005
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2005.50.4.1159
Subject(s) - thalassiosira weissflogii , ammonium , nitrate , limiting , stoichiometry , nitrogen , nutrient , composition (language) , chemistry , chlorophyll a , nuclear chemistry , analytical chemistry (journal) , zoology , botany , biology , environmental chemistry , biochemistry , phytoplankton , linguistics , philosophy , mechanical engineering , organic chemistry , engineering
We grew Thalassiosira weissflogii to steady state over a range of Fe‐limiting conditions with nitrate or ammonium as the N source. Nitrate‐dependent cells had faster Fe‐uptake rates, contained significantly higher intracellular Fe quotas, and grew faster than cells cultivated with NH 4 + when Fe was most limiting. Under these conditions, carbon (C) : chlorophyll a ratios and the minimum fluorescence yield per chlorophyll a increased, but N source had no effect on either parameter. The ratio of variable to maximum fluorescence (F v F m −1 ) declined little with Fe limitation m even when T. weissflogii was grown at 25% of its maximum rate (µ max ). C:N ratios were higher in nitrate than in ammonium‐grown cells and were constant at all Fe levels. Protein was independent of Fe and N, and amino acids were lowest in cells using NO 3 − . The P content of T. weissflogii (mol P L −1 cell volume) increased by 1.5 times as Fe became most limiting to growth, causing N: P and C: P ratios to decline significantly. The elemental stoichiometry for Fe‐limited new production of T. weissflogii (0.25µ max ) was thus 70C : 10N : 5.9Si : 1P : 0.00074Fe (by mols) compared with 97C : 14N : 4.7Si : 1P : 0.029Fe for nutrient‐replete conditions. Uptake rate ratios of NO 3 − : PO 4 3− showed the same dependence on Fe as the cellular N: P quotas, decreasing as [Fe] decreased. Iron limitation influenced the elemental composition of this marine diatom and will alter the assimilation ratios of C, N, and P in the high nitrate, low chlorophyll regions of the sea.