Vol. 53 - Alaska Resources Library and Information Services

the second pre-spill sample (immediate pre-spill sample in this investigation) to the third
post-spill sample (September, 1982).
No progressive changes in adjusted dry weights or
weight-length regressions were observed in S. groenlandicus from the other bays.
decrease in weight per unit shell length or adjusted to a standard shell length indicates a
decrease in the condition or nutritional status of the mollusc.
A
Although Bay 7 was
considered a reference bay, it did receive 50-100 ppb of dispersed oil in the first few days
after the discharge (Green et al., 1982). S. groenlandicus from the 7-meter depth in Bay 7
accumulated hydrocarbons to higher levels immediately after the spill than did the same
species from the 7-meter depth in the other bays (See Section 2 of this report). S.
groenlandicus from Bays 9 and 10, which received much higher levels of dispersed oil,
probably were narcotized and/or stopped filtering, and therefore became less
contaminated than animals from Bay 7.
S. groenlandicus differed from the other filterfeeding
mollusc studied, Mya truncata, in that it preferentially retained in its tissues a
high molecular weight saturated hydrocarbon assemblage as well as the toxic highly
alkylated naphthalenes, phenanthrenes, and dibenzothiophenes.
partially explain the apparent impact of oil on S. groenlandicus from Bay 7.
Whereas S. groenlandicus
These observations may
is a filter-feeder and accumulates petroleum
hydrocarbons primarily from the water, Macoma calcarea is a deposit-feeder and
accumulates petroleum hydrocarbons primarily from contaminated sediments.
Thus, as
reported in the bioaccumulation section of this report, M. calcarea from Bay 7 did not
accumulate significant body burdens of hydrocarbons because very little of the waterborne
hydrocarbons entering the bay were deposited in the sediments. In the other three
bays, substantial amounts of oil were deposited in bottom sediments and M. calcarea
became the most heavily contaminated. Hydrocarbon body burdens in the deposit-feeders
increased between the first and second post-spill samplings. Cross and Thompson (1982)
and Cross et al. (1983) reported that M. calcarea from Bay 7 underwent a seasonal cycle
of increasing length-adjusted tissue dry weight between August and September in both
1981 and 1982. This probably represented a natural cycle of fattening and gonadal
maturation in the animals.
However, M. calcarea from the other bays did not show
evidence of this cycle, and in clams from Bay 9, there actually was a decrease in lengthadjusted
tissue dry weight between August, 1981 (pre-spill) and September, 1981 (second
post-spill sampling).
These results suggest that petroleum contamination of sediments
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