Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 4 3 2007 10.5194/bg-4-283-2007 http://www.biogeosciences.net/4/283/2007/ http://www.biogeosciences.net/4/283/2007/bg-4-283-2007.html http://www.biogeosciences.net/4/283/2007/bg-4-283-2007.pdf 283 296 2007-05-24 DON as a source of bioavailable nitrogen for phytoplankton D. A. Bronk bronk@vims.edu J. H. See P. Bradley L. Killberg Department of Physical Sciences, The College of William and Mary, Virginia Institute of Marine Science, P.O. Box 1346, Gloucester Point, VA 23062, USA Geo-Marine Inc., 2201 K. Avenue, Suite A2, Plano, TX 75074, USA Relative to inorganic nitrogen, concentrations of dissolved organic nitrogen (DON) are often high, even in regions believed to be nitrogen-limited. The persistence of these high concentrations led to the view that the DON pool was largely refractory and therefore unimportant to plankton nutrition. Any DON that was utilized was believed to fuel bacterial production. 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