Gschwend%20thesis.pdf

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and a subsurface maximum of about 2 ~g/kg at 70 - 90 m. Hence fairly
. low phytoplankton productivity was encountered. Due to variable
sample contamination of the volatiles on the western Equatorial
Atlantic cruise, only pentadecane provided useful data (Table 2-1).
Surface values varied considerably and were as high as 40 ng/kg.
Some thermocline samples contained 20 to 30 ng/kg, while most of the
samples between 100 and lOOO m had less than 3 ng/kg. Curiously, 3
of the 4 deep water samples showed elevated concentrations of penta-
decane between 10 and 30 ng/kg.
The hydrographic data (figure 2-4) from the
Peru upwelling region
demonstrated the presence of active upwelling inshore of station 3
during the sampling. The nutrients were relatively high at station i
and then reduced in the offshore stations to relative minima at stations
4 and 6 (figure 2-5). An oxygen deficient subsurface layer was
encountered at all stations at about 100 m (figure 2-6). Chlorophyll a
was very high (greater than 10 ~g/kg) in the surface waters offshore
of station 2 (figure 2-6). Phaeophytin did not reveal any marked
trends beyond being higher in surface seawater than in deeper samples
(figure 2-6).
The seawater samples from the upwelling region near Peru contained
detectable levels of several groups of volatile organic compounds.
The individual C2~alkylated benzenes were found at less than LO ng/kg;
surface seawater samples contained 2 to 3 times more of these aromatic
hydrocarbons than did samples from 1000 m (figure 2-7).
An unknown compound was found to be coeluting with ethyl benzene
in several surface seawater samples. Mass spectral evidence suggested
that this was an octatriene. A molecular weight of l08 was determined
for this compound based on the presence of m/e 109 (M+I), 137 (M+29) 0