| Summary: | <p>At each station, CTD casts measured temperature, salinity and PAR. Water samples collected at depths of 700, 500, 300, 200, 100, 80, 60, 40, 20 m, and the surface were filtered and preserved for nutrient analysis. In the upper 80 m, water samples were gravity filtered and preserved for microscopic enumeration of both Trichodesmium colonies and free trichomes. For each nitrogen fixation sample, the number of puffs, number of rafts, and amount of carbon was measured. Individual carbon per colony values were estimated by regressing carbon content with number of puffs and number of rafts. Bowtie carbon content per colony was assumed the same as puff carbon per colony.</p> <p>The sampling program included daily stations with associated nitrogen fixation experiments beginning at approximately 10:00 a.m. local time. Trichodesmium colonies for on-board incubation experiments and genetic assays were picked individually with pipettes from water collected at the surface (5-15 m) and at depth (20-70 m). Surface and deep samples were collected by pumping water through a 150 µm sieve on OC469 and by MOCNESS with 150 µm nets on OC471. Additional surface samples were taken by net tow (150 µm) on both cruises. After initial collection, the largest and most intact individual colonies were isolated using eyedroppers and transferred to filtered seawater for incubation experiments in order to assemble sufficient biomass to produce measurable rates. Nitrogen fixation was measured by acetylene reduction assay (Capone and Montoya, 2001).</p> <p><strong>Related References:</strong></p> <p>Capone, D. G. and J. P. Montoya, 2001: Nitrogen fixation and denitrification. Marine Microbiology, J. H. Paul, Ed., Academic Press, Methods in Microbiology, Vol. 30, 501-515, doi: <a href=\"http://dx.doi.org/10.1016/S0580-9517(01)30060-0\" target=\"_blank\">http://dx.doi.org/10.1016/S0580-9517(01)30060-0</a>, URL: <a href=\"http://www.sciencedirect.com/science/article/pii/S0580951701300600\" target=\"_blank\">http://www.sciencedirect.com/science/article/pii/S0580951701300600</a>.</p> <p><strong>Related Dataset:</strong></p> <p>Tricho N Atlantic - OC471: http://www.bco-dmo.org/dataset/505567</p>
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