Gschwend%20thesis.pdf

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Zsolnay (l973, 1976) has reported the correlation of chlorophyll a
and nonaromatic hydrocarbon concentrations in seawater samples from
the upwelling region off Northwest Africa and in the slope waters
between the Gulf Stream and Nova Scotia. This has been taken as
evidence for a phytoplanktonic source of these hydrocarbons. Plots
of pentadecane concentration versus chlorophyll ~ for the western
Equatorial Atlantic and the Peru cruises are shown in figures 2-l0 and ll.
If one considers all samples from a region, the correspondence in
these parameters is very poor. However, if the sample locations are
noted, additional insight may be found. In the western Equatorial
Atlantic, 4 of t.he 5 high-pentadecane observations were from shallow
samples of the two westernmost stations (l3 and 24). Possibly these sites were
populated with a biological community capable of greater pentadecane
production than the stations to the east. Similarly, if the Peru
upwelling region samples are divided by sample locations, the station
6 samples fall into one region while the other surface samples are
found in another. Thus, the relationship of pentadecane and chloro-
phyll a seems to be dependent on site specific parameters.
The station 3 surface samples from the Peru upwelling region
were collected at different times of day relative to the other shallow
samples (about 18: 00 instead of IO :00 for the 5-m sample and vice
versa for the 20-m sample). Time of day appears to affect the
chlorophyll ~ and phaeophytin values. These pigments always built
up during the day (Gagosian, pers. comm.) and consequently show
uncharacteristically high values at station 3/5 m and low values at
3/20 m. Pentadecane seems to vary in the opposite fashion (i. e. ,
diminishing during the day). Sample 3/5 m had quite low pentadecane
concentration relative to other neighboring samples while the 3/20 m
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