Vol. 53 - Alaska Resources Library and Information Services

Such information can be used to gauge the movement of crab larvae in
currents relative to origins and surface speeds of oil movement. These
exercises have been done by Leendertse and Liu (1981) and Sonntag, et
al. (1980).
Following hypothetical oil spills or well blowouts in these models, oil
is moved by winds and currents, mixed by storms, and transported to the
benthos by several processes. It may then impact crab populations by
direct exposure, loss of food and over-competition, or accumulation in
tissues and gametes. Oil concentrations in the water column and benthic
sediments are modeled as a function of the magnitude of an initial oil
spill and its duration, time of year, location, and loss of certain oil
fractions by processes such as volatilization. Model outputs show the
trajectory and extent of oil coverage and concentration at various times
after each hypothetical mishap. From data and assumptions on lethal
levels, distribution and abundance of animals, sensitive life-history
stages and physiological events (e.g., molting of crustaceans), predictions
are made of the proportion of a year-class or population killed
and the eventual ramifications such losses pose to commercial fisheries.
Scenarios considered by participants of the 1981 Anchorage OCSEAP
Workshop included only spills or blowouts that released 50,000 barrels
(bbl) which is a quantity far less than might be expected from mishaps
involving modern tankers. Oil spill in scenarios used during the North
Aleutian Shelf synthesis meeting in Anchorage (March 1982) were even
smaller. Spills of 10,000 bbl were modeled by Pelto and Manen (1983)
and covered relatively small areas of the NAS (20 km by less than 1 km).
Spill
scenarios modeled by the 1980 Asilomar Workshop included both a
100,000 mt (1.11 x 106 bbl) spill over two days and a release of 5,000
mt day[superscript]-
1
(55,500 bbl) for 20 days (Sonntag, et al. 1980). After mixing
oil to 50 m depth and a loss of 25 percent of the volatile fraction, an
area of 7,500 km 2 was polluted at or above 0.2 mg 1- 1 (considered a
lethal threshold in that model).
If as suggested by Armstrong, et al.
399