Methodology for Underway Bottle Data

L.A. Codispoti (codispot@hpl.umces.edu)
Horn Point Lab. University of Maryland Center for Environmental Science
P.O. Box 775
Cambridge, MD 21613-0775
410-221-8479

General Comments:

This readme file pertains to the bottle salinity, Winkler dissolved oxygen,
and nutrient data taken from the R/V Revelle's underway pumping system during
JGOFS/AESOPS cruises RR06 (Survey I), RR07 (Process I), RR08 (Survey II) and 
RR09 (Process II). Temperatures from the sensor mounted in the intake near the 
bow are also included.  Other instrumental data (e.g. conductivity) were taken 
from sensors near the intake and in the Revelle's hydro lab, but they are not 
included here since this submitter was not able to perform QA/QC on these data, 
including the temperatures from the sensor near the intake (bow sensor).
Investigators interested in the instrument data may wish to contact Bob Williams
[bob@odf.ucsd.edu] or Prof. John Morrison [john_morrison@ncsu.edu].

No units are given for salinity in this report because the most recent
definitions of salinity define it as a dimensionless number.  Winkler oxygen
values are reported in ml/liter. Nutrient values are  reported in micromolar.
The nutrient values in micromolar can be converted to micromoles per kg, by
combining a temperature of 20 deg. C and the salinity of the sample to compute
density and then dividing the value in micromolar by this number. 

Methods:

In general, the methods employed for the bottle salinity, Winkler dissolved
oxygen, and nutrient analyses did not differ significantly from those described
in the JGOFS protocols that were distributed in 1994 (UNESCO, IOC Manual and
Guide #29).  Minor differences included the following: 1) The protocols give one
a choice of adjusting nutrient methods so that calibration curves are strictly
linear, or opting for more response and taking into account non-linearities.  We
chose the latter method.  2) No corrections were made for "carryover" between
nutrient samples run on the Technicon Autoanalyzer.  Carryover effects in our
nutrient analyses are generally less than ~2% of the concentration difference
between adjacent samples, and were minimized by arranging samples in depth order
and by running some samples in duplicate.  3) Calibration and re-calibration of
volumetric ware were not exactly as described in the JGOFS protocols, but all
volumetric flasks, maxipettors, and dosimats were calibrated.  4) Duplicate
oxygen samples were not routinely drawn.  5) The JGOFS protocols do not describe
an automated technique for the analysis of ammonium concentrations.  We employed
the Berthelot reaction using a method somewhat similar to the method described
by  Whitledge et al. (1981, Whitledge, T.E., Malloy, S.C., Patton,  C.J. and
Wirick, C.D. Automated Nutrient Analyses in Seawater. Brookhaven National
Laboratory Rept.  BNL 51398, 216pp.).  


Salinity:

Salinities were determined with Guildline Autosal salinometers.  New vials of
standard sea-water were used to standardize before and at the end of every run. 

Dissolved oxygen:

The Winkler dissolved oxygen apparatus was built under the direction of Bob
Williams (bob@odf.ucsd.edu) and supplied by the Scripps Institution of
Oceanography's (SIO) Ocean Data Facility (ODF) group.  This system is computer
controlled and detects the end-point photometrically.  Temperatures of the
thiosulfate and standard solutions are automatically monitored by this system.  

Nutrients:

Note that the terminology used to describe nutrients has become somewhat loose
over the years and that silicate = silicic acid, dissolved silicon or reactive
silicate, and phosphate = reactive phosphorus. The terms ammonium and ammonia
tend to be used inter-changeably, and the sum of the two is determined by our
methodology.  Both species co-exist in seawater, but under normal conditions
ammonium is present in higher concentrations.  Nutrient analyses were performed
on a 5-channel Technicon II AA system that was modified and provided by Doug
Masten (doug@odf.ucsd.edu) of the ODF group at the Scripps Institution of
Oceanography. 

Queries:

Questions about these data may be addressed to:

Dr. L. A. Codispoti
Horn Point Lab
University of Maryland - Center for Environmental Science
P.O. Box 775
Cambridge, MD 21613-0775
Codispot@hpl.umces.edu
410-221-8479