Vol. 53 - Alaska Resources Library and Information Services

2.2 Laboratory Methodology
2.2.1 Sediment Analysis
Homogenization was accomplished by kneading the sample bag for several
minutes. Following digestion of organics, the samples were wet sieved
on a No. 230 sieve. Material passing through the sieve was then transferred
to a settling chamber; the remainder was dried at 103°C, cooled,
weighed and placed on a nest of sieves of decreasing size (Nos. 5, 7,
10, 14, 18, 25, 35, 45, 60, 80, 120, 170 and 230). The material retained
on each sieve was then weighed. Approximately 30 grams of the
material which passed through the No. 230 sieve were transferred to a
settling chamber; 5 ml of sodium hexametophosphate was added and diluted
to 1 liter with deionized water. The samples were allowed to soak for
12 hours. A settling cylinder was then filled, thoroughly mixed,
returned to vertical position and 25 ml aliquots withdrawn at specified
times and depths. The aliquots were placed in a tared 50 ml beaker
which was covered and dried in an oven at 90°C. The beakers were then
reweighed after cooling for one hour.
2.2.2 Larval Counts
The preserved samples were first either subsampled using a Folsom
plankton splitter or rough sorted for decapod larvae in their entirety.
The decision of whether to sort the entire sample or to split it depended
on its size and condition. The general, subjective rule governing
this decision was that if the sample was "clean" and had a volume
greater than 0.15 liter, it was subsampled. Samples were considered
"clean" if the volume of gelatinous zooplankton was low and there were
no large phytoplankton aggregations, both of which would interfere with
splitting.
Most samples were counted in their entirety; however, as needed,
samples
were sequentially divided with the plankton splitter until 100 to
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