Vol. 53 - Alaska Resources Library and Information Services

spills need consideration.
The effects of oil spills in the nearshore zone are well documented
(see Clark, 1982). Incorporation of oil into the subtidal sediment and
its subsequent loss are functions of the circumstances of the particular
spill and the energy of the nearshore zone. Because of its high energy
the nearshore zone of the North Aleutian Shelf appears likely to have oil
incorporated into and readily lost from subtidal sand following a spill.
Whereas prediction of the probable occurrence, magnitude and extent of an
oil spill reaching the nearshore subtidal habitats of the smallest
juvenile king crab is beyond the scope of this study, there is little
doubt that should a significant spill reach the nearshore zone there could
be substantial acute, lethal and sublethal effects. Substantial immediate
effects including the oiling and mortality of intertidal crabs occurred
during the AMOCO CADIZ spill (See review by Conan et al, 1981).
Substantial mortality of juvenile king crab would require water column
concentrations of 4.2 ppm total hydrocarbons by IR, the 96-h LC 50 for
moribundity found by Brodersen et al (1977) for juvenile king crab exposed
to WSF of Cook Inlet crude oil. The concentrations of oil in the
sediment that would produce mortality in the juvenile king crab are not
known. If a spill should produce acute mortality in the smallest juvenile
king crab, any substantial loss of yearling crab could be felt as decrease
in year class strength in the commercial fisheries 8 years later when the
crabs would have reached harvestable size.
Chronic indirect effects persisting beyond a spill could derive from
loss or reduction in the macro or meiofaunal food of the smallest
juveniles. Meiofaunal groups vary considerably in their resistance to oil
contamination and can recover quickly (Giere, 1979). In studying a
refinery effluent Dicks and Hartley (1982) report that oligochaetes had
decreased density at stations near the refinery and showed a gradient in
density paralleling that of sediment concentrations of aliphatic
hydrocarbon. The immunoassay identified oligochaetes as a dietary item
for the smallest juvenile crab. In subtidal recruitment studies
Vanderhorst (Unpublished data; see Vanderhorst, 1984) found significant
reductions in the numbers of species of polychaetes, mollusks and
crustaceans recruiting into sand contaminated with crude oil at total oil
levels initially at 2000 ppm and falling to below 1000 ppm in 3 months.
Densities of a crustacean and a polychaete selected a priori for detailed
analysis were reduced to 1/4 and 1/3, respectively, of the densities in
control sand. From intertidal recruitment studies Vanderhorst et al.
(1981) predicted full recovery of the infauna to take 31 months following
an initial contamination of the sand at 1800 ppm. An oil spill in the
shallow nearshore zone can reasonably be expected to reduce the density of
food important to juvenile crabs, but prediction of the extent of such
restriction in the crab's food supply requires prediction of the salient
features of such a spill.
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