Vol. 53 - Alaska Resources Library and Information Services

overnight or even for several days in a refrigerator before freezing. The most variable
set of samples was that from the first post-spill collection. Examination of the field log
book indicated that these samples were collected over a 10-day period (from Bay 9 on
8/28, 29 and 31/81; from Bay 10 on 8/29-30/81; from Bay 11 on 8/21/81; and from Bay 7
on 8/31/81). The simulated spill of oil alone in Bay 11 was on 8/19/81 and the simulated
spill of dispersed oil in Bay 9 was on 8/27/81.
Thus, clams from the bay receiving oil
alone (Bay 11) were sampled two days after the spill, while those from bays receiving
dispersed oil were sampled up to four days after the spill. Thus, it is difficult to compare
acute responses of clams to the different treatments.
Collection of the pre-spill and
second post-spill samples also took place over several days, but the interpretive problem
in these cases is less severe. It also should be pointed out that samples for hydrocarbon
analysis were not always taken at the same time as samples for biochemical analysis at a
given bay and station.
Despite these problems, some conclusions can be drawn from the results of
these biochemical studies on Mya truncata. Based on results of the biochemical analyses,
truncate soft-shell clams were not severely stressed by either dispersed or undispersed oil
at the contaminant levels attained in the BIOS experiment. Although all treatment groups
were exposed to and subsequently accumulated some petroleum, and therefore there was
no true control or reference group of animals, clams from Bay 7 were the least heavily
contaminated. Therefore, they can be used, in lieu of a true reference. Clams from Bay
11 (undispersed crude oil) differed the most from clams from Bay 7, particularly in the
second post-spill sample. Clams from Bay 10 (dispersed crude oil) became more heavily
contaminated with petroleum hydrocarbons than clams from the other dispersed oil bay
(Bay 9) and showed greater differences than the latter in several biochemical parameters,
as compared to clams from Bay 7. These differences were most marked in the first postspill
survey. Thus, we can conclude that chemically dispersed oil may cause more severe
acute effects than undispersed oil in benthic infaunal molluscs, but longer-term impacts
of undispersed crude oil may be more severe than those of chemically dispersed oil. This
is undoubtedly related to the observations documented in the Section 2 of this report that
petroleum contamination of filter-feeding molluscs was greatest in the bays receiving
dispersed oil and reached a peak in the first post-spill samples, decreasing in the second
post-spill samples. On the other hand, contamination of clams in the bay receiving oil
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