Vol.1 part 4-5 - Department of Invertebrate Zoology

Lead-210 was determined by measuring
the growth of the bismuth-210 (Bi-210) daughter (Beta
of 1 .2 Mev) . The Bi-210 activity was determined utilizing
a gas proportional anti-coincidence counting system
. The system has a background of approximately 0 .5
cpm and a counting efficiency of 30% for Bi-210 beta
particles . Final assays were made 20 to 40 days after the
isolation of Pb-210 (i .e . to allow sufficient Bi-210
growth) from the sediment samples .
2. Biota
a. Collection
Fish and epifaunal samples were collected by
diving, angling, and trawling . The proposed method of
obtaining pelagic fish attracted to the platforms was by
angling, with emphasis on snappers and grouper . However,
after little angling success on Cruise I, this was
modified to include diving on a special "fishing"expedition,
Cruise II-B . When "pelagic" fish were not angled,
divers speared fish at platforms to meet the contract requirements
for "pelagic" fish . Divers also collected attached
bivalved mollusks to meet "epifauna" requirements
when these were not met by trawling for epifauna
and demersal fish .
Equipment (fishhooks, spears, tongs, etc .)
was of stainless steel whenever possible and rigorously
cleaned plastic ; i .e ., acid-washed ice chest for temporary
storage and uncoated nylon trawls and dive bags .
Samples taken during diving went directly from the
water into ice chests and those from trawls into a stainless
steel sorting tray where they were immediately
hand-sorted using acid-washed rubber gloves . Individual
samples were then placed in prelabeled, acid-washed
polyethylene bags and frozen . For both trace metals and
hydrocarbons samples, care was taken to avoid contamination
from on-deck equipment and activities by immediate
processing in an established routine . Experience
indicates two keys to avoiding on-deck contamination :
maintaining the sample processing area upwind of engine,
galley and other exhausts, and frequent washdown
of everything with plenty of seawater .
b .
Initial Preparation and Digestion
(1) Pelagic Fish
On arrival at the onshore laboratory,
transfer of custody documents was completed and all
samples were inventoried according to the preprinted
sample inventory form and stored in a walk-in freezer .
For analysis, five individual sample specimens were
thawed and dissected on a clean bench using Tefloncoated
forceps and stainless steel surgical instruments .
Tissues (flesh, gills, liver, and gonads) were removed
and pooled in acid-washed, preweighed 250-m1 polyethylene
beakers . Pooled samples were composed of individual
organisms of approximately the same size and developmental
stage which were collected from approximately
the same area . During dissection procedures,
separate instruments were used for separate species and
tissue groups to avoid cross-contamination . Between
use, all dissecting instruments were cleaned according to
normal laboratory procedures then washed with O.1N
nitric acid and rinsed with distilled water . Before dissection
procedures began, all samples were rinsed with distilled
water .
The first dissection procedure was to
open the visceral cavity from the gular region to the vent
with stainless steel scissors . The alimentary system was
snipped above the stomach and pulled from the abdominal
cavity, mesenteries when necessary, exposing the
liver and gonads (where developed) . This allowed for
excision of the liver and gonads . The second dissection
procedure involved removing filets of skeletal muscle
from the lateral musculature. The epidermis and scales
were removed and the muscles from both sides of the
specimen were fileted with a stainless steel knife. The
third dissection procedure was excision of the gills. The
operculum was raised and the gill arches removed at the
dorsal and ventral connections of the gill cavity with
stainless steel scissors . Gills were collected from all specimens,
whether the gonads were developed or not, as a
backup for insufficient gonadal tissue . The entire gill
structure-arches, rakers, and gill filaments-was analyzed
.
After the five specimens within a group
were dissected, each tissue-liver, flesh, gonads, and
gills-was placed in a pre-weighed 250-m1 beaker . The
beakers were weighed to obtain wet weights of the tissues
. Beakers were sealed with polyethylene sheets, frozen
(0 C) and placed in a Labconco Model 75010 freeze
dryer for 48 hrs . The freeze-dried samples were reweighed
to determine water loss, then ground to ensure
complete mixing of the sample in a Virtis "45" homogenizer
(The Virtis Company, Inc ., Gardiner, New York)
using stainless steel blades .
The possibility of Cr, Fe, and Ni contamination
of the samples through microcorrosion of the
stainless steel blades was investigated by Tillery (1980x) .
Shrimp tissues were prepared with the Virtis "45" homogenizer
and were also ground with an agate mortar
and pestle . No evidence of contamination was found .
The finely ground samples (0.5 g) were
weighed into tared PyrexO ashing boats and placed into
a low temperature asher (LTA-505, LFE Corporation,
Waltham, Massachusetts) . They were ashed for 16 hrs
at 450 watts of forward power using an oxygen plasma .
The asking boats were removed from the asher and 1 ml
of 70% HN03 (Suprapur) was added to solubilize the
ash and retain it in the asking boat during the transfer to
a clean bench . The ash was quantitatively transferred
into a Teflon bomb with distilled water and 3 ml of 70%
HN03 (Suprapur) was added . The Teflon bomb was
sealed and placed in a steam bath (90-110 C) for 2 hrs .
The bomb was allowed to cool and the digestant was
quantitatively rinsed into a 15-m1 polyethylene centrifuge
tube using three rinsings (both cap and cylinder) of
distilled water . The sample was centrifuged for 10 min
at 3000 RPM and the supernatant decanted into a 25-m1
volumetric flask without disturbing the precipitate . The
precipitate was rinsed with 2 ml of distilled water and recentrifuged
for 10 min . This rinse was then decanted
into the volumentric flask and brought to volume with
distilled water . This solution was used to determine the
different analyte metals using flame or flameless AAS
and NAA . Concentrations of the different elements determined
the method of AAS analysis . Aliquots were
taken for Ba and V analyses by NAA .
(2) Macroepifauna and Demersal Fish
Pooled samples of macroepifauna and
demersal fish were composed of individual organisms of