Gschwend%20thesis.pdf

-197-
markedly during the late-winter phytoplankton blooms of 1977 and 1978.
.-.
Oxidation of algal unsaturated fatty ac!d~ may also produce these alde-
hydes in coastal seawater as suggested for open-ocean seawater.
In addition, C12-C15 aldehydes occurred at very high concentrations
in February, 1978. Tridecanal was recovered at more than 100 ng/kg.
Cultures in log and stationary growth phase of Thalassiosira nordenskioeldii,
the predominant diatom found in the late-winter bloom, did not produce
these aldehydes. Oxidation by zooplankton or photochemically-produced free
radicals may be necessary to produce these aldehydes from algal metabolites.
Dimethyl di-, tri-, and tetrasulfides were found at up to 20 ng/kg
in coastal seawater. The observation that the first 2 hours of stripping
frequently recovered less of these polysulfides than Æn additional 2 hours
of stripping led to the conclusion that formation of these volatile sulfur
compounds must occur within the sample. Marine microorganisms are known
to produce methyl mercaptan, which may be oxidized to dimethyldisulfide.
Reaction 0~methyl mercaptan or dimethyldisulfide with elemental sulfur
will yield other polysulfides. These polysulfides may also be derived
from degradation of other polysulfide metabolites.
Ci- and C1-benzenes in Coastal Seawater
Additional work was performed to describe the sources of the C2- and
C3-benzenes to coastal seawater. Short-term studies carried out over
sumer weekends showed that large inputs of these pollutants occurred at
these times (2-10 fold concentration. increases). The highest concentrations
ever found coincided with ski boat activity in the immediate vicinity of
the sampling site. The C2- and C3-benzene isomer distribution of the