Aquatic Sciences Meeting, Albuquerque 2001
| PC13 Phytoplankton: Trace Metals and Biochemistry |
| Date: Thursday, February 15, 2001 |
| Location: Southwest Hall |
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| Lenes, J, M, University of South Florida, St. Petersburg, USA, lenes@seas.marine.usf.edu |
| Darrow, B, P, University of South Florida, St. Petersburg, USA, bdarrow@seas.marine.usf.edu |
| Cattrall, C, , University of South Florida, St. Petersburg, USA, chris@monty.marine.usf.edu |
| Heil, C, A, University of South Florida, St. Petersburg, USA, cheil@seas.marine.usf.edu |
| Callahan, M, , University of South Florida, St. Petersburg, USA, callahan@seas.marine.usf.edu |
| Vargo, G, A, University of South Florida, St. Petersburg, USA, vargo@seas.marine.usf.edu |
| Byrne, R, H, University of South Florida, St. Petersburg, USA, byrne@seas.marine.usf.edu |
| Prospero, J, M, University of Miami, Miami, USA, jprospero@rsmas.miami.edu |
| Bates, D, E, University of Miami, Coral Gables, USA, bates@physics.miami.edu |
| Walsh, J, J, University of South Florida, St. Petersburg, USA, jwalsh@seas.marine.usf.edu |
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| IRON FERTILIZATION AND THE TRICHODESMIUM RESPONSE ON THE WEST FLORIDA SHELF |
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| The role of Trichodesmium in nutrient dynamics of oligotrophic continental shelves remains a mystery. Due to a high iron demand, laboratory studies of Trichodesmium had shown increased nitrogen-fixation in response to Fe-stimulation. Summer delivery of iron, in the form of Saharan dust, to offshore surface waters of the West Florida Shelf may provide a similar explanation for Trichodesmium blooms. During ECOHAB field studies, background levels of 0.1-0.5 nmol Fe kg-1 were found at the surface during periods of minimal dust delivery in May 2000 and October 1999. In contrast, total dissolved iron concentrations of ~16 nmol Fe kg-1 were measured at the West Florida shelf-break after a July 1999 Saharan dust event. The Trichodesmium response following this dust event was a 100-fold increment over background biomass, reaching a surface stock of ~20 colonies l-1. These diazotrophs excrete up to ~50% of their nitrogen-fixation as dissolved organic nitrogen. Consequently, their associated surface summer DON pools were found to be 3-4 fold greater than background stocks of ~5 umol DON kg-1, compared to nitrate stocks of <0.5 umol NO3 kg-1. |
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