Gschwend%20thesis.pdf

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On the other hand, a phytoplankton source cannot be ruled out.
Little work has been done to isolate volatile compounds from phyto-
plankton.
Specific Volatiles; C6-CiO Aldehydes
The C6-CIO straight chain aldehydes were observed in the Peru
upwelling region samples predominantly in surface waters (figure
2-9). These aldehydes may be produced by phytoplankton. The linear
correlation coefficients for hexanal and heptanal with chlorophyll ~
were 0.55 and 0.76 respectively. Other workers have found aldehydes
as constituents of freshwater diatoms (Kikuchi et al., 1974) and
fresh water yellow-green algae (Collins and Kalnins, 1965).
Alternatively, these aldehydes may be intermediate oxidation
products of algal organic matter by heterotrophs. For example ,
hexanal has been obtained from the metabolism of linoleic and linolenic
acids (Jadhav et aL., 1972). In order to see if these aldehydes
might be produced by remineralization processes in the seawater off
Peru, the aldehyde concentrations were plotted against oxygen
(figure 2-12). Rather than the expected inverse correlation, a strong
direct correlation was observed for hexanal and heptanal (linear
correlation coefficients of 0.78 and 0.89). Octanal showed a weaker
correspondence (r = 0.67), whereas the trace levels of nonanal and
decanal precluded useful testing. The direct correlation of aldehyde
concentrations with oxygen suggests that these compounds were not
produced by heterotrophs during remineralization. Instead, the
observed correlation suggests another source for the C6-CIO aldehydes,
chemical oxidation. Possibly higher oxygen concentrations cause this
reaction to proceed more quickly and therefore result in higher aldehyde
levels.