Gschwend%20thesis.pdf

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A third set of seawater samples was collected at 6 stations in
March, 1978 on cruise 73 of the R/V Knorr to the upwelling region off
the coast of Peru (figure 2-1). A single 30-liter Niskin was used.
Water was drawn from the bottle through a polypropylene tube and an
in-line filter (precombusted 142 mm glass fiber filter in a stainless
steel holder) which were rinsed with a portion of the sample. Reagent
bottles (2-liter) with ground-glass stoppers were filled with seawater,
poisoned with O. 5ml HgCl2 solution (40 mg HgCl2 per ml water), and
then tightly stoppered. Filtering and poisoning were done to prevent
biological activity from altering the volatile organic compound
content of the samples during storage.
. 0
Samples were stored at 4 C in
the dark for 3 to 6 weeks until being returned to the lab at Woods Hole.
IIi order to check for the effects of filtering and poisoning
treatments, some replicate samples were left untreated while others
were only poisoned. Untreated samples were always drawn first, then
unfiltered samples, and finally those that were filtered.
Samples for salinity, oxygen, nutrients, chlorophyll ~, and
phaeophytin were drawn from the same Niskin bottle and analyzed on
board.
Analysis of Volatile Organic Compounds
The seawater samples from the Sargasso Sea and the western
Equatorial Atlantic were analyzed for volatile organic compounds
using the "Tenax method." Details of this method are provided in
Appendix I. It is chiefly adapted from methods reported in the
literature (Zlatkis et al., 1973; Bellar and Lichtenberg, 1974; May
et aL., 1975).