Transcript N 2 + 8H + + 8e

This is a presentation created by Prof. Karen Orcutt (Univ of
Southern Mississippi, Dept of Marine Sciences) for the NSTA
workshop titled 'COSEE: The Oceans, They Are A-Changin':
How Might This Affect You?' on Sat, March 21, 2009. The target
audience was middle and high school science educators. Prof.
Orcutt focused the often misunderstood concept of nitrogen
fixation by open ocean primary producers - in particular the
contribution of planktontic filamentous cyanobacteria called
Trichodesmium that live in colonies and contribute significantly to
the global nitrogen cycle by "fixing" nitrogen gas (N2) into more
biologically useful nitrogen-containing compounds (e.g., NH3,
ammonia). She also describes the roles of other oceanic
biological pump and microbial loop "players" such as
heterotrophic bacteria, dinoflagellates and diatoms.
Nitrogen Fixation
Marine Nitrogen Fixation
N2 + 8H+ + 8e- + 16ATP
2NH3 + H2 + 16 ADP + 16 Pi
Marine Nitrogen Fixation
N2 + 8H+ + 8e- + 16ATP
2NH3 + H2 + 16 ADP + 16 Pi
• Important source of N to the ocean
Marine Nitrogen Fixation
N2 + 8H+ + 8e- + 16ATP
2NH3 + H2 + 16 ADP + 16 Pi
• Important source of N to the ocean
• Requires energy (P)
Marine Nitrogen Fixation
N2 + 8H+ + 8e- + 16ATP
2NH3 + H2 + 16 ADP + 16 Pi
• Important source of N to the ocean
• Requires energy (P)
• Needs Fe ≈ 34 Fe atoms
Tuft
Puff
T. thiebautii
Morphologies of
Trichodesmium
http://www.whoi.edu/science/B/people/ewebb/Tricho.html
Trichodesmium form large
surface accumulations
that can be seen from ships ….
http://www.futura-sciences.com/fr/news/t/oceanographie-1/d/les-tresors-biologiques-delocean_9300/
http://www.marine.uq.edu.au/marbot/marineplants/cyanobacteria2.htm
……and seen from aircraft……..
……..and from space!
Photo NASA
Photo: NASA
Katagnymene pelagicum now Trichodesmium
Photo: Annette Hynes
Katagnymene spiralis
now Trichodesmium
Photo: Ed Carpenter
Aphanizomenon flos-aquae
N2 fixation
Heterocysts
http://www.fimr.fi/en/tietoa/algaline_s
euranta/lajistoraportit/lajistoraporttiar
kisto/2006/en_GB/3705/
http://www.soes.soton.ac.uk/staff/tt/nf
/structure/nodspum.htm
Nodularia sp. (N. spumigena)
Richelia inside Hemiaulus sp.
Photo by Dr. Dave Caron
Unicellular cyanobacteria nitrogen fixers
Crocosphaera watsonii (WH8501)
http://www.whoi.edu
/science/B/people/e
webb/
2-6 µm
Photo Kjell Gundersen
Heterotrophic bacteria ( and -Proteobacteria))
Photo: Dr. Frank J. Jochem
AGU Ocean Sciences Meeting 2000, San Antonio, Texas, January 2000
Capone 2008
CO2
N2
Surface
CO2
Fe
P
Phytoplankton
photosynthesis
Deep
© KAREN M. ORCUTT
CO2
+
Nutrients
N
Bacterial
remineralisation
CO2
+
Nutrients
Diatoms - Bacillariophyceae
ASLO image library
www.aslo.org
http://www.olympusmicro.com/primer/technique
s/hoffmangallery/diatom.html
Dinoflagelltes - Dinophyceae
ASLO image library
www.aslo.org
http://www.biologycorner.com/bio1/no
tes_plantlikeprotists.html
http://ux.brookdalecc.edu/staff/sa
ndyhook/plankton/summer.htm
http://www.whoi.edu/science/B/peopl
e/ewebb/Tricho.html
NASA/Goddard Space Flight Center
The SeaWiFs Project and ORBIMAGE
Scientific Visualization Studio.
http://cosee.umaine.edu/cfuser/index.cfm