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Molecular assessment of phosphorus and iron physiology in Trichodesmium populations from the western Central and western South Atlantic
Author(s) -
Webb Eric A.,
Jakuba Rachel Wisniewski,
Moffett James W.,
Dyhrman Sonya T.
Publication year - 2007
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.2007.52.5.2221
Subject(s) - trichodesmium , transect , phosphorus , diazotroph , biology , phosphorus deficiency , limiting , nitrogen fixation , phosphate , chemistry , nutrient , biochemistry , ecology , bacteria , genetics , mechanical engineering , organic chemistry , engineering
Trichodesmium is capable of responding to low phosphorus (P) and low iron (Fe) concentrations through the induction of alkaline phosphatase (AP) activity (an enzyme that hydrolyzes inorganic phosphate from phosphomonoesters) and the IdiA protein (an iron deficiency protein that putatively binds iron), respectively. We monitored AP activity and IdiA expression as molecular diagnostics of P and Fe stress in Trichodesmium field samples on a transect from the western central to the western South Atlantic and compared the expression of these markers with physical, chemical, and N 2 fixation measurements. Trichodesmium AP activity was detected at many stations, whereas IdiA expression was not. Incubation additions of inorganic P at one station resulted in a loss of AP activity and an increase in N 2 fixation. Our data suggest that P, and not Fe, is the constraining factor limiting Trichodesmium N 2 fixation along most of the transect. These results support previous modeling efforts predicting that diazotrophs in this region are P‐stressed and further validate the use of molecular diagnostics of nutritional physiology, in concert with more traditional approaches, for identifying constraints on marine N 2 fixation.