Gschwend%20thesis.pdf

sample was enriched relative to adj acent samples of the
-65.,
same depth.
This atypical result may be caused by organisms which are particularly
rich in pentadecane (or somehow capable of producing pentadecane)
and which migrate vertically during the day. This interpretation
also suggests the involvement of zooplankton in the formation of
pentadecane.
Three deep samples from the western Equatorial Atlantic (13/
2376 m, i 7 /1896 m, and 24/1923 m) showed unexpectedly high values
of pentadecane. Other workers (Iliffe and Calder, 1974; Barbier et
al., 1973) have reported increased total hydrocarbon concentrations
with depth after an initial subsurface concentration decrease. These
higher concentrations may represent relic hydrocarbons produced by
organisms in surface seawater at the site of deep-water
formation.
Blumer et aL. (1971) noted the relative stability of the saturated
hydrocarbons, and these compounds have been proposed as water mass
tracers (Illife and Calder, 1974). It seems unlikely that in situ
production or remineralization of materials transported from the
surface could generate the pentadecane found at these depths.
Specific Volatiles; C2-benzenes
The individual C2-benzenes were found at less than 10 ng/kg.
The mean value for the meta + para xylenes in 5- and 50-m samples
from off Peru was 4 ng/kg. Values declined to less than 3 ng/kg at
lOOm.
Less than 2 ng/kg were found in the deepest samples. This
~
pattern suggests a surface or atmospheric source. Biological sources
of these compounds are unknown. Since the recently upwelled waters
at station i also have 4..5 ng/kg of these compounds ,the transfer
from the source must be very rapid. If the atmosphere :were the
l , .