Dataset: N15_uptake
Deployment: TT049

See Platform deployments for cruise specific documentation

   PI:              Raymond Sambrotto
   of:              Lamont-Doherty Earth Observatory
   dataset:         N-15 uptake rates for nitrate, ammonium and urea;
                    Concentration of ammonium, urea and particulate C and N
   dates:           July 18, 1995 to August 11, 1995
   location:        N: 22.5346  S: 9.9258  W: 57.3012  E: 68.75
   project/cruise:  Arabian Sea/TTN-049 - Process Cruise 4 (Middle SW Monsoon)
   ship:            Thomas Thompson
 
   Note from R. Sambrotto:
 
   The data served as of August 12, 1997 have been modified in the
   following ways from the data served prior to this date:
   1) More particulate nitrogen, particulate carbon and nanomolar
   ammonium data have been added that were not included with the
   initial data release.
   2) The uptake rates for nitrate, ammonium and urea needed to be
   recomputed using the correct 15N isotope addition concentrations.
 

  Methodology:

      1. Ammonium - nanomolar ammonium concentrations, as measured by a
spectrophotometric procedure based on the Berthelot reaction followed
by an extraction step to concentrate the indophenol.
         References: 
		  a) Brzezinski, M.A. (1987) Colorimetric
		     Determination of nanomolar concentrations of
		     ammonium in seawater using solvent extraction.
		     Marine Chemistry, 20, 277-288.
		  b) Selmer, J.S. and F. Sorensson (1986) New
		     Procedure for extraction of ammonium from natural
		     waters for 15N isotopic ratio determinations.
		     Applied Environmental Microbiology, 52, 577-579.

      2. Urea - urea concentration as measured by a spectrophotometric 
procedure based on the diacetylmonoxime reaction.
         Reference: 
		    Whitledge, T.E., S.C. Malloy, et al. (1981)
		    Automated nutrient analysis in seawater. Department
		    of Energy and Environment, Brookhaven National
		    Laboratory, Upton, NY.

      3. N-15 uptake - 

            A. Uptake rates for nitrate and urea were measured by incubation
experiments to follow the incorporation of trace additions of N-15
labeled substrate into particulate material collected by Whatman GF/F
filters.
         Reference: 
		    Sambrotto,R.N., J.H. Martin, et al. (1993) Nitrate
		    utilization in surface waters of the Iceland Basin
		    during spring and summer of 1989. Deep-Sea Research II.
                    Vol. 40, No.1/2, 441-457.

            B. Methodology for ammonium rates was similar to that for
nitrate and urea, except that modified isotope dilution model was used
to calculate uptake.
         Reference: 
		    Glibert, P. M., F. Lipschultz, et al. (1982).
		    Isotope dilution models of uptake and remineralization
                    of ammonium by phytoplankton. Limnology and 
                    Oceanography 27: 639-650.

      4. Particulate carbon and nitrogen - the concentration of either
particulate carbon or nitrogen as measured by collection on Whatman
GF/F filters, followed by Dumas combustion, cryogenic separation and
manometric analysis.