Vol. 53 - Alaska Resources Library and Information Services

decision based on GC 2 . Oil levels of ~1.0 ppm would contain individual component
concentrations (i.e., n-alkanes) of ~.01 ppm (or 10 ng/g). Due to significant biogenic
background in the GC 2 traces, this level of individual components was often too low to
see in the GC 2 traces. Thus UV/F becomes a key to assessing oil concentrations in
sediments. However, in several cases in Bay 7 sediments, low UV/F levels (~0.3 ppm),
generally associated with background levels, were shown by GC 2 to contain small amounts
of oil. The weathering of oil while in transit to Bay 7 with resulting loss of water-soluble
aromatics and a concomitant decrease in UV/F response caused whatever oil was seen in
Bay 7 sediments to be relatively enriched in saturates (not detectable by UV/F). Thus the
two techniques of UV/F and GC 2 proved to be an extremely powerful complementary set.
Water-borne oil in Bay 11 was initially confined to the surface (0-2 meters) layer
during which time large-scale transport of oil to the benthos via sorption and sinking did
not occur. Through large volume water samples, low levels (ppb) of oil were detected in
mid-depth and bottom waters largely in a particulate form, prior to any possible crosscontamination
from the dispersed oil spill occurring a week later. That oil did impact the
sediment in Bay 11 prior to the dispersed oil spill is evident from uptake patterns of all of
the benthic animals, especially those of the deposit-feeders Macoma and Nuculana and of
the filter-feeder Serripes which all revealed uptake of oil, albeit at lower levels relative
to those which were acquired in the dispersed oil scenario, prior to any possible crosscontamination
from Bays 9 and 10. We do know that the dispersed oil's influence was farranging
including a transient water column impact at Bay 7 causing elevated levels of oil
in all benthic biota, especially the filter-feeders Mya and Serripes. Thus it may be logical
to "subtract" the observed Bay 7 animal levels from the Bay 11 values to derive a "pure"
Bay 11 result for the second post-spill sampling. Using this logic, it can be concluded that
although low levels of oil are acquired in Bay 11 by the filter-feeders, the major Bay 11
impact is on the deposit-feeders which are more closely linked to the sediments and which
acquire weathered oil from off of the beach face.
The most significant findings of the study concern the relationship between
water-borne levels of oil, sediment concentrations and levels in benthic biota. Initial
uptake of oil by Mya and Serripes is from the water column wherein oil is acquired
through pumping of contaminated seawater through gills. Most of this oil initially resides
in the animal's gut as confirmed through Serripes dissections. Chemically, even the initial
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