This is a presentation created by Prof Karen

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 (N 2) into more biologically useful nitrogen-containing compounds (e. g. , NH 3, 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 N 2 + 8 H+ + 8 e- + 16 ATP 2 NH 3 + H 2 + 16 ADP + 16 Pi

Marine Nitrogen Fixation N 2 + 8 H+ + 8 e- + 16 ATP 2 NH 3 + H 2 + 16 ADP + 16 Pi • Important source of N to the ocean

Marine Nitrogen Fixation N 2 + 8 H+ + 8 e- + 16 ATP 2 NH 3 + H 2 + 16 ADP + 16 Pi • Important source of N to the ocean • Requires energy (P)

Marine Nitrogen Fixation N 2 + 8 H+ + 8 e- + 16 ATP 2 NH 3 + H 2 + 16 ADP + 16 Pi • Important source of N to the ocean • Requires energy (P) • Needs Fe ≈ 34 Fe atoms

Tuft T. thiebautii Puff 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-de -locean_9300/ http: //www. marine. uq. edu. au/marbot/marineplants/cyanobacteria 2. 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 N 2 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 (WH 8501) 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

CO 2 N 2 Surface Fe P Phytoplankton photosynthesis Deep © KAREN M. ORCUTT CO 2 + Nutrients N Bacterial remineralisation CO 2 + 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/bio 1/no tes_plantlikeprotists. html http: //ux. brookdalecc. edu/staff/san dyhook/plankton/summer. htm

http: //www. whoi. edu/science/B/peopl e/ewebb/Tricho. html

NASA/Goddard Space Flight Center The Sea. Wi. Fs Project and ORBIMAGE Scientific Visualization Studio.

http: //cosee. umaine. edu/cfuser/index. cfm