EPA Report
April, 1979
UPTAKE OF KEPONE FROM SUSPENDED SEDIMENTS BY
OYSTERS AND OTHER BIVALVE MOLLUSCS
by
Dexter S. Haven and Reinaldo Morales-Alamo
Virginia Institute of Marine Science
Gloucester Point, Virginia 23062
Grant Number R804993010
Project Officer
Tudor T. Davies
Gulf Breeze Environmental Research Laboratory
Gulf Breeze, Florida 32561
Gulf Breeze Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Gulf Breeze, Florida 32561
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DISCLAIMER
This report has been reviewed by the Gulf Breeze Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not sig-nify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
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ACKNOWLEDGEMENTS
The contributions to this work by Dr. Michael E. Bender, Head of the
VIMS Division of Environmental Science and Engineering and Dr. Robert J.
~9^
lluggett, Head of the VIMS Department of Ecology -*«o Pollution and Project
Manager for this research are gratefully acknowledged. Appreciation is also
expressed to Harold D. Slone and his assistants for sample analysis, to
Gloria B. Rowe for her assistance in transcription of this manuscript and to
Kay B. Stubblefield and her staff at the VIMS Art Departnent for preparation
of the figures. Final copy of this report was prepared by the VIMS Report
Center.
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SECTION 1
INTRODUCTION
This report presents results of experiments on uptake of Kepone by
bivalve molluscs conducted between October 1977 and February 1979 by the
Virginia Institute of Marine Science under-a contract with the Environmental
Protection Agency (Grant Identification Number: R804993010). An earlier
report submitted to the EPA contained the results of similar experiments
conducted during the period between October 1976 and October 1977 (Haven and
Morales-Alamo, 1977).
Between October 1977 and February 1979 twelve laboratory experiments
were conducted with the American oyster Crassostrea virginica in trays
receiving suspended sediments contaminated with Kepone. The contaminated
sediments were collected from the James River in the vicinity of Hopewell.
~Two
To similar experiments were conducted with the Asiatic clam Corbicula
manilensis and one with the coot clam Mulinia lateralis. Data on
concentrations of Kepone in oyster biodeposits were collected from five
experiments using contaminated sediments in suspension. In nine of the
experiments with oysters and in the one with M. lateralis, samples of the
contaminated animals were placed in uncontaminated river water for periods of
time ranging between one and three weeks to study depuration.
In addition to the laboratory studies, two series of experiments were
conducted on piers at Skiffes Creek (Fort Eustis Port) and Deep Creek
(Menchville Marina) in which water from the creeks was pumped over trays
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X
:upneatz
holding individuals of the wedge clam Rangia cujineata and oysters,
respectively.
Another group of experiments was conducted at three stations in the
James River (Wreck Shoal, Point of Shoals and Deep Water Shoal) in which
oysters were held in wire trays on the river bottom. Sediment-collecting
containers were also positioried7"on the bottom, adjacent to these trays.
Many details on materials, methods and procedures were described in the
EPA Progress report for the period October 1976 - October 1977Q (Haven and
Morales-Alamo, 1977). Consequently, they have been omitted from this report
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SECTION 2
MATERIALS AND METHODS
Uptake Studies Using Sediment Suspensions in the Laboratory
The experimental procedures and data analysis in these experiments are
given by Haven and Morales-Alamo (1977). Contaminated sediments came from
the vicinity of Hopewell, at Jordan Point and Bailey Creek, in the James
River.
The apparatus used in laboratory studies in which sediment suspensions
contaminated with Kepone flowed over animals in plastic trays was described
earlier (Haven and Morales-Alamo, 1977) and is illustrated again in Figure 1
of the present report. A minor change made in the apparatus consisted of
replacement of the rectangular mixing chamber with a circular one. Water
flowed directly into the circular chamber and out into the experimental trays
through a standpipe with a 1.2 cm diameter opening.
Studies of Accumlation of Kepone in Oyster Biodeposits
Five studies were conducted in which biodeposits produced by oysters
receiving contaminated sediments in suspension were collected and analyzed
for Kepone contents. The oysters were held in the large, compartmentalized,
trays. Biodeposits and sediments settling out by gravity were collected
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rET£
n
"
daily in separate containers. The aggregates accumulated in the containers
at the end of each contamination period were analyzed for Kepone. Each day,
after biodeposits and sediments had been collected, every compartment was
cleaned of any remaining material.
In two experiments conducted between November 1978 and January 1979.no
data were collected for gravity-settling sediments. In the first case, the
experiment was conducted as a part of another study and the sediments
settling out by gravity were not collected. In the other experiment the
concentration of sediments in suspension was so low that volume of sediments
settling out were not measurable.
Uptake Studies Using Water Pumped From Two Contaminated Creeks
Field uptake studies were conducted on piers at tributary creeks of the
James River: Skiffes Creek and Deep Creek, located on the north shore of the
river, 46 and 30 km from the mouth, respectively (Figure 2). The apparatus
used at both stations was the same (Figure 3).
A galvanized steel pipe (A) buried in the bottom and fastened to the
pier structure held in place a small submersible pump (B) about 20-30 cm from
the bottom. Water depth at the Ft. Eustis pier (Skiffes Creek) was about
3.7 m. At the Menchville Marina dock (Deep Creek) it was about 1.5 m. Water
was pumped continuously into a 38-1 rectangular plastic aquarium (C) from
which it overflowed continuously back into the creek. Water was pumped
intermittently out of the aquarium by a submersible pump (D) into a 49-1
plastic storage carboy (E). Water collected in the carboy was used for
determination of Kepone in the suspended particulate matter. Pump D was
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3
connected to an interval timer (F) that regulated pumping at intervals that
fluctuated randomly between two and eight seconds out of every hour.
Water was siphoned out of aquarium C through small-bore tubing (G) into
one or two plastic trays (H) holding the experimental animals and into a
similar control tray without animals. These trays were identical to those
used to contaminate oysters and darns with sediment suspensions in the
laboratory as described in Haven and Morales-Alamo (1977). Water overflowed
out of the trays into a collector trough (I) that emptied into the creek
through a piece of plastic tubing (J). The whole system was enclosed in a
locked^large plywood box that protected it from weather and people.
The experimental site was visited daily. Hydrographic measurements as
well as measurements of the water flow into the experimental trays were made
at that time. The carboy with water accumulated since the previous day was
replaced with an empty one and taken back to the laboratory for extraction of
the particulate matter by centrifugation.
After determination of the total volume contained in the carboy, the
water was centrifuged the same day using a high-speed centrifuge with a
continuous-flow attachment and operated at 14,000 RPM with water flowing at a
rate of 1 1/m. The sediments collected each day were combined for the period
of time that the experimental animals were exposed to contamination, which
was usually- seven days, but at times was shorter or longer. After removing
salts by rinsing in de-ionized water, the sediments were dried, weighed and
analyzed for Kepone.
At the end of an exposure period, samples of the molluscs were taken
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from the trays and deposits (sediments and biodeposits) that had accumulated
in each tray were collected. The trays were rinsed with creek water before
animals were put back. Height (distance between umbo and valve margin) of
molluscs in the sample y&re measured and their meats analyzed for Kepone.
The deposits collected were washed free of salt, dried and also analyzed for
Kepone content.
At the end of each week, new uncontaminated animals were placed in one
of the trays from which all previous occupants had been removed. Thus, that
tray never held animals longer than one week. The data on these animals were
used for comparison with the data obtained by holding other animals for
longer periods of time in similar trays.
Studies in Which Oysters were held in Trays on the James River Bottom
A series of field studies was conducted in which uncontaminated oysters
and/or Rangia clams were exposed to contamination in trays on the river
bottom at three stations in the James River (Wreck Shoal, Point of Shoals and
Deep Water Shoal; Figure 3). At the same time suspended sediments settling
out in the vicinity of the tray were collected in a sediment trap placed on
the bottom adjacent to the tray.
Oysters were lowered to the river bottom at each of the three stations
in a tray made of wire. A 2.5 cm mesh wire cover was fastened to the tray
top. The tray was 103 cm long, 48 cm wide and 10 cm deep and had a 2.5 cm
mesh size. A rope from the tray to the water surface was tied to a stake and
was used to lifj? the tray out of the water for sampling.
Rangia clams were lowered to the bottom at Deep Water Shoal (Figure 2)
AFT
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"—' m ft.
in a galvanized-wire bag with a 2.5 cm mesh. The bag was 61 era long, 30.5 cm
wide and 10 cm deep. A rope from the bag was tied to a stake at the water
surface.
The sediment trap consisted of two plastic bottles held in a truncate
pyramid made of concrete (Figure 4). The base of the pyramid was 44.5 cm on
two sides and 43 cm on the other" and' its height was 16.5 cm. The top was 15
x 15 cm. Two holes side by side on the top of the trap measured 7.3 cm in
diameter and 13.5 cm in depth. Two 500-ml plastic bottles, 16 cm high and
7.3 cm in diameter with a mouth 4.3 cm in diameter were inserted in the holes
to serve as sediment collectors. Tape wrapped around the bottle served to
hold it in the hole by friction. The top edge of the bottle protruded
2.5 cm out of the hole. A rope from the trap bridle was tied to the same
stake that the oyster tray or Rangia bag was tied to.
These stations were visited weekly except when weather or other
unfavorable circumstances interfered and samples of animals were collected
for Kepone analysis. A new group of animals was placed in the tray or wire
bag when the last ones of a group were removed.
At each sampling time the bottles in the sediment trap were removed and
replaced with empty ones. In the laboratory, the sediments collected in one
of the two bottles were washed free of salts, dried and subsequently analyzed
(/V-tL^y
for Kepone.. Sediment in several of the other bottles v&&e stored in a
refrigerator and subsequently selected ones were analyzed for particle size.
Samples for size analysis were washed free of salt and shaken for 24
hours in a wrist-action shaker after addition of sodium hexametaphosphate as
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• 1
r
a dispersant. Sediments were then wet-sieved through a 63^< screen to
separate sands from silt and clays. Sands were oven-dried at 87°C and
weighed without further screening. The silt-clay fraction was transferred to
a 1000 ml cylinder and analyzed by the pipette method (Krumbein and
Pettijohn, 1938).
Additionally, samples of oy'steVs from natural beds and bottom sediments
were collected and analyzed for Kepone. Oysters were dredged up and a sample
of the sediments brought up in the dredge was collected by scooping up a
portion of the surface layer identifiable by its brownish coloration.
Source of Experimental Animals
All oysters used in these experiments were collected from the Piankatank
River (Figure 5) and were found to be free of Kepone at the start of all
experiments. Rangia clams were collected from the fresh water reaches of the
Rappahannock River about 68 km upriver (Figure 5), and were also free of
Kepone.
Corbicula clams were collected from the James River about four km above
Hopewell. Corbicula could not be found further upriver between that point
and Richmond. As expected, the Corbicula collected had Kepone in their
meats. They were held for three weeks in running freshwater in the
laboratory receiving supplementary starch suspensions as food prior to use in
the experiment. However^ they still had Kepone after that period of time.
The Mulinia clams were hatched and reared at the Virginia Institute of
Marine Science laboratories in Wachapreague, Virginia and came from water
with a salinity of 30 °/oo. They were held in standing water in a
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refrigerator (10°C) at Gloucester Point while the water salinity was lowere
by replacement with York River water. Every 24 hours the water was changed
and an increasing proportion of York River water was added to the container
until the salinity was lowered to that of the York River which was 20 °/oo at
the time. That was accomplished in four days. At the end of that period
they were taken out of the refrigerator and allowed to reach room
• ~ ;•>
temperature. Then they were placed under running York River water at ambient
temperature, which at the time was 28°C.
Preparation of Laboratory Sediment Suspensions
Sediment suspensions used in laboratory experiments were prepared
following in the manner described in Haven and Morales-Alamo (1977). To
improve homogeneity of dosage through the duration of an experiment, slight
modifications were made in the procedure described there. The sediments from
all bags brought in from the James River were mixed together in a large tub.
Small plastic bags were filled to a volume of approximately 500 ml and
numbered in the order they were filled.
Only sediments collected on the same data were used in any one
experiment. Sediment suspensions for the studies were prepared at the same
time from two bags by pairing bags from opposite ends of the numerical
progression created when the bags were filled; for example, the first bag
filled was paired with the last one filled. Thus, successive pairs of bags
showed a simultaneous progression from the lowest number up and the highest
number down.
The resulting paired stock suspensions in 6000 ml flasks were combined
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by siphoning their contents simultaneously into a series of five flasks in
equal volumes (2000 ml) and into two extra containers in volumes
approximately 400 and 200 ml, respectively. Samples in the two extra
containers were used for Kepone and sediment concentration analyses.
The stock suspension in the 2000 ml flasks was the material introduced
into the experimental trays by means' of a peristaltic pump. It was usually
oi . ~) u^ *
diluted with tap water by factors ranging between iwc and 12 before being C t~-H*/fl
pumped into the experimental trays. The dilution factor used depended on the
concentration of Kepone in the stock solution and the final concentration
desired. The flow of York River water used was kept constant and control of
the final suspension was, therefore, determined by the concentration of the
stock suspension being pumped into the trays and the rate at which it was
pumped .
The ratio of particulate material in the stock suspensions prior to
entering the mixing chamber to particulate material in the York River water
at the same point was very large. The concentration of particulate matter in
the stock suspensions usually ranged between 15,000 to 40,000 mg/1 with an
average between 25,000 and 30,000 mg/1 while that in the York River water
usually ranged between 5 and 15 mg/1, with an average of 7 to 10 mg/1.
Therefore, sediment particles in the York River water constituted an
insignificant factor (usually less than 10%) in the final composition of the
particulate matter flowing over the oysters in the experimental trays.
Consequently, the composition of the material found in the oysters' gut at
any time would be, for all practical purposes, that of the original sediments
used to prepare the stock suspensions.
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Determination of Kepone Concentration in Sediment Suspension
The concentration of Kepone in the diluted sediment suspension flowing
over the experimental animals was determined by computation of the product of
four factors:
Kc = (s-c}:, .(kc) (dx) (d2)
where
KC = computed Kepone concentration in diluted suspension, in ppb ( g/1)
sc = sediment dry weight per unit volume in stock suspension, in Kg/1
kc = Kepone concentration determined analytically for dry sediments in
stock suspension, ppm (f!g/g).
d^ = factor by which stock suspension was diluted prior to being pumped
into mixing chambers.
d2 = factor by which the suspension being pumped into mixing chambers
was diluted; determined by the flow rate at which it was being
pumped and the flow rate of York River water flowing simultaneously
into the mixing chamber.
The factor d2 was controlled in each experiment by selection of
peristaltic pump settings that would deliver a desired flow rate of the
sediment suspension into the mixing chamber. Flow of river water was
maintained relatively constant while the flow rate of contaminated sediments
was adjusted so that trays would receive sediment suspensions at different
rates.
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T
Determination of Kepone Concentration in Suspended Sediments
The computations used for determining the concentration of Kepone in the
diluted sediment suspensions flowing over the experimental animals in
laboratory trays are described in Haven and Morales-Alamo (1977). The
following clarification is necessary. The value obtained for concentration
of Kepone in the sediment suspension is given as parts-per-billion. It
should be understood that this represents mass of Kepone per unit volume of
water (J4g/l~). The assumption has been made that the Kepone present is
associated only with the particulate matter. The section entitled
Preparation of Data for Analysis in Haven and Morales-Alamo (1977) is
pertinent to this subject and should be consulted as needed.
A 24*e""field studies in which creek water was pumped into trays with
animals at Skiffes Creek and Deep Creek, the concentration of Kepone in the
sediment suspension flowing into the trays was established as follows: The
concentration of sediments in the water was determined by dividing the weight
of the dried sediments collected by centrifugation by the volume of water
centrifuged. This value was then multiplied by the concentration of Kepone
in the dried sediments to obtain the concentration of Kepone in terms of mass
per unit volume of water. As was the case in laboratory studies, all the
Kepone in the sediment suspension flowing over the animals was assumed to be
associated with the particulate fraction of the suspension.
Determination of Concentration Factors
Two types of concentration factors were computed to compare the •
concentration of Kepone in the meats of the bivalves and in their biodeposits
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with the concentration in the contaminated sediments and the suspensions
derived from them. One was based on the concentration of Kepone per unit
volume of suspension flowing into the experimental trays after the
contaminated sediments were diluted with seawater. The other one was based
A
on the concentration of Kepone actually associated with the sediment
particles (also termed "dry sediments" in our tables and figures) used to
prepare the suspensions.
These two concentration factors represent analogies of the
bioconcentration and bioaccumulation factors in wide use in the literature on
uptake of chemical compounds by aquatic organisms (see, for example, Bahner,
JLL J*L' > 1977). The bioconcentration factor is defined by Hamelink (1977) as
the concentration of a compound in the organism at the steady state divided
by the concentration of the compound in the water (generally understood to
mean in solution in the water). In this case, the compound is being taken
directly from the water by the organism. The bioaccumulation factor is
defined by Bahner- et al. (1977) as the concentration of the compound in a
predator divided by the concentration of Kepone in that predator's prey. In
this case, the compound is taken by an animal through ingestion of another
animal containing that compound.
The processes by which bivalves would take up Kepone from solution in
water and from the fraction adsorbed on the surface of sediment particles are
different from each other. Nevertheless, the technique for computation of
, . ~> .
the corresponding concentration factors is similar, .therefore, the I y
concentration factors may be considered analogous. In both instances the
mass of Kepone in an organism is compared to (and divided by) a known mass of
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"RAi
•a
fj
Kepone contained in a unit volume of water. This analogy justifies our use
of a concentration factor based on the concentration of Kepone in sediment
suspensions diluted to a variety of levels.
Contamination of bivalves by ingestion of sediment particles with Kepone
adsorbed to their surfaces is also akin to the process of bioaccumulation.
Therefore, a concentration factor Based on the Kepone associated with the
sediment particles in suspension (ignoring their concentration per unit
volume of water) can be considered analogues to the bioaccumulation factor as
defined above.
The concentration factor that takes into account the dilution of the
sediment suspensions is emphasized throughout this report. The concentration
factor based exclusively on the Kepone associated with sediment particles is
used to a lesser extent when required to explain certain specific points.
Emphasis on the former was required because the concentration of Kepone per
unit volume of suspension had a direct bearing on the quantity of Kepone
taken up by the bivalves while the concentration in the sediments did not, by
itself, determine the quantity found in bivalves.
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REFERENCES
Bahner, L. H., A. J. Wilson, Jr., J. M. Sheppard, J. >'. Patrick, Jr., L. R.
Goodman and C. F. Ualsh. 1977. Kepone^ bioconcentration, accumulation,
loss, and transfer through estuarine food chains. Ches. Sci.
18:299-308.
Bender, M. E., R. J. Iluggett and W. J. Mar?is, Jr. 1977. KenoneR residues
in Chesapeake Bay biota. In: Proc. 10th National Shellfish Sanitation
Workshop [D. S. Wilt, Ed.], Hunt Valley, Md . , U.S. Food and Dru.e
Administration, pp. 66-71.
Hamelink, J. L. 1^77. Current bioconcentration test methods and theory.
In: Aquatic Toxicology and Hazard Evaluation, ASTM STP 634 (F. L. Mayer
and J. L. Hamelink, Eds.).
Hamelink, J. L., R. C. Waybrant and R. C. Rail. 1971. A proposal: Kxchanpe
equilibria control the decree chlorinated hydrocarbons are biologically
magnified in lentic environments. Trans. A^er. Fish. Soc. 100:207-214.
Haven, D. S. and R. Morales-Alamo. 1966a. Aspects of biodeposition bv
oysters and other invertebrate filter feeders. Lirnnol. Oceanogr.
ll:4S7-498.
and . 1966b. Use of fluorescent particles to trace oyster
biodeposits in marine sediments. J. Cons. Intl. Explor Mer 30:267-269.
and . 1972. Biodeposition as a factor in sedimentation of fine
suspended solids in estuaries. In: Environmental Framework of Coastal
Plain Estuaries (B. W. Nelson, Ed.), deol. Soc. America Memoir 133, pp.
121-130.
and . 1977. Uptake of Kepone from suspended sediments by oysters,
Rangia and Macoma. In: The Role Uptake of Kepone in Estuarine
Environments (R. J. Hugpe'tl'V Project Manager), Proceedings of the Kepone
Seminar II, September 1977,/U.S. Environmental Protection Apency, Region
III, pp. 394-447. .
Haven, D. S., F. 0. Perkins, R. Morales-Alamo and >'. V.'. Rhodes. 1977.
Coliform depuration of Chespapeake Bay oysters. In: Proc. 10th
National Shellfish Sanitation Workshop, [D. S. Wilt, Ed.], Hunt Vallev,
Md., U.S. Food and Drue Administration, pp. 49-59.
yyv^rvXA^jL^JC
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Xracniter, J. N., D. s. Haven and R. Morales-Alamo. O-'P in preparation).
Sediment mixing, by estuarine invertebrate species and communities.
Krumbein, V. C. and F. J. Pettiiohn. 1938. Manual of Sedimentary
Petrography. Appleton-Centnry-Crofts , New York, 5^9 pp.
Mayer, F. L. 1976. Residue dynamics of di-2-ethyIhexyl phthalate in fathead
minnows (Pimephales promelas). J. Fish Res. Bd. Canada 33:2610-2613.
Nichols, M. M. 1972. Sediments of the James River estuary, Virginia. In:
Environmental Framework of Coastal Plain Estuaries (B. W. Nelson, EC'.),
Geol. Soc. America Memoir 133, Dp. 16°-212.
Nichols, M. M. and R. C. Trotman. 1977. Kepone in James River Sediments.
An annual progress report to EPA. In: The Role of Sediments in the
Storage, Movement and Biological Uptake of Kepone in Estuarine
Environments (R. J. tlugRett, Project Manager), Proceedings of ''eoone
Seminar II, September 1977, U.S. Environmental Protection Agency, Region
III, pp. 365-382.
Onishi, Y. and R. N. Ecker. 1978. The movement of Kepone in the James
River. In: The Feasibility of Mitigating Kepone Contamination in the
James River Basin (G. W. Dawson, Project Director). Appendix A, p.
VTI-1 to VII-85. Report by Pacific Northwest Laboratory (Batelle
Memorial Institute, Richland, Washington, to the U.S. Environmental
Protection Agency.
Schneider, M. J. and G. W. Dawson. 1978. Ecological effects of Kepone.
In: The Feasibility of Mitigating Kepone Contamination in the James
River Basin (G. W. Dawson, Project Director). Appendix A, p. VIII-1
to VIII-27 . Renort by Pacific Northwest Laboratory (Batelle Memorial
Institute), Richland, Washington, to the U.S. Environmental Protection
Agency.
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SECTION 3
RESULTS
Laboratory Experiments with Sediments in Suspension
Results from laboratory experiments in which oysters, Corbicula
manilensis and Mulinia lateralis were exposed to suspensions of sediments
contaminated with Kepone are given separately below for each species.
No laboratory experiments with Rangia cuneata were conducted in 1978-79
However, the data collected in 1976-77 are re-introduced in this section to
present some aspects not covered in our previous report.
Unless specified otherwise, the concentration factor used throughout
this section is based on the concentration of Kepone per liter of sediment
suspension. The data are separated into series as a convenient way to
distinguish between experiments conducted at different times.
Crassostrea virginica—
Fourth series—This series of experiments was conducted between 6
October and 4 November 1977 at ambient York River water temperatures. Mean
weekly water temperatures ranged between 15.7 and 19.9°C (Table 1). Mean
weekly salinity ranged between 22.9 and 24.0 °/oo.
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Oysters, ranging in height between 6 and 9 cm, were subjected to two
different concentrations of Kepone in sediment suspensions. The mean hourly
concentration for the different weekly periods ranged between 0.05 and 0.08
//g/1 in one tray and between 0.19 and 0.25,«g/l in the other. Oysters in a
third tray receiving uncontaminated York River water were maintained as a
control.
At the lower mean concentrations (0.05-0 .OS^g/l) oysters concentrated
Kepone by factors ranging between 1372 and 1805 (Table 2). Concentration in
the animal tissues leveled off after the second week of exposure (Figure 6) .
This curve is similar to those obtained in" earlier experiments where a
leveling off after the first or second week was usually suggested. The
highest mean concentration in oysters in any weekly period was 0.13/xg/l (wet
weight).
At the higher mean concentrations (0 .19-0.25/ig/]joysters concentrated T
Kepone by factors ranging between 914 and 1581 (Table 2). Concentration in
the animal tissues increased with the time of exposure through the four weeks
duration of the experiment, up to a level of 0.40/<.g/g (Figure 7). This
increase is associated with the increase in mean hourly concentration of
Kepone in the sediment from one week to another.
Uncontaminated oysters were introduced at the start of the third and
fourth weeks into the tray receiving the higher of the two concentrations of
Kepone and also at the start of the fourth week into the tray receiving the
lower concentrations of Kepone. This was done to compare accumulation of
Kepone between newly-exposed oysters and oysters that had been already
exposed to contaminated sediments for the preceding two and three weeks.
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In all three instances, the newly-introduced oysters showed Kepone
levels only slightly lower than those found in the oysters that had been
exposed to contamination for the preceding two or three weeks (Table 3,
Figure 7).
As part of the fourth series of experiments, oysters were taken out of
the trays in which they were-being exposed to contaminated sediment
suspensions and transferred for depuration to trays receiving uncontarninated
York River water. This was done at the end of the second and third weeks of
exposure to contamination. The three groups of oysters thus subjected to
depuration for one week showed reductions in the level of contamination
between 76 and 80 percent (Table 4, Figure 8). Not much difference was
evident between oysters that had been receiving the higher concentrations of
Kepone and those that received the lower concentrations in terms of percent
reduction. The level attained after depuration by those that received the
lower concentration was only slightly lower than in those that received the
higher concentrations.
Fifth series—The purpose of this series of experiments was to study the
rate at which oysters contaminated with Kepone in the laboratory depurated
when held in flowing, Kepone-free water, also in the laboratory. For that
reason, the concentration of Kepone in the sediment suspensions flowing over
the oysters during contamination was not measured.
The experiments were conducted between December 8, 1977 and January 13,
1978. York River water temperature was raised with heat exchangers to a
range in weekly means between 17.2 and 19.5°C (Table 5). Mean weekly
salinity ranged between 16.3 and 18.4 °/oo.
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Fifty-four oysters were placed in a large tray (81 cm long, 55 cm wide
and 9 cm deep) receiving suspensions of sediment contaminated with Kepone.
At the end of one week (December 15), samples of the oysters were taken out
from Kepone analysis. Eighteen of the oysters were transferred to another
tray receiving Kepone-free oysters from the York River. Another group of 18
Kepone-free oysters from the original stock collected from the Piankatank
River was introduced into the contamination tray at the same time. These
newly-introduced oysters were properly identified to separate them from those
which had already been in the tray for one week.
At the end of the second week (on December 23), samples of oysters from
each of the two groups in the contamination tray were taken out for analysis.
Samples of depurating oysters were also taken out for analysis. The oysters
remaining in the contamination tray were transferred to trays receiving clean
York River water.
Figures 9 and 10 and Table 6 sunmarize the data on uptake and depuration
of Kepone by oysters in the fifth series of experiments. After the first
week of exposure to contamination, three samples of oysters showed an average
concentration of Kepone of 0.42 ppm (Figure 10). Following one week of
depuration, the level of Kepone in samples of this group of oysters decreased
s •—••w
by 65% to 0.14 ppm. In thef followingN two/ weekly period of depuration, the
concentration decreased at a slower rate of 0.07 in the second week and to
0.03 in the third week.
Samples of oysters that remained in the contamination tray for two weeks
showed a mean concentration of 0.68 ppm (Figure 10, solid circles).
Following one week of depuration the average concentration of Kepone in
-------
samples of these oysters decreased by 56% to 0.30 ppm. After the second week
of depuration, concentration had decreased by 85% to 0.10 ppm. During the
third week of depuration there was a slight aberrant increase in
concentration from 0.10 ppm to 0.19 ppm, which probably represents chance in
sampling.
Oysters introduced into'CKe-contamination tray at the end of the first
week an'd sampled one week later had a mean concentration of Kepone of 0.58
ppm (Figure 10). This value was significantly higher than that for oysters
analyzed after exposure during the first week of the experiments, but similar
to that for those exposed for two weeks. We do not have any data for the
-)
concentration of Kepone in the sediment suspensions, but we do|(now that the >
two groups of oysters sampled at the end of the second week were receiving
the same concentration in suspension. The concentration in suspension during
the first week was probably lower than that for the second week.
After one week of depuration, the mean Kepone concentration in samples
of oysters from this group decreased by 75% to 0.14 ppm (Table 6). The rate
of decrease was much lower during the following two weeks. After two weeks
of depuration the mean concentration of Kepone was 0.095 (a total reduction
of 83%) and after three weeks it was 0.09 (a total reduction of 84%).
Sixth series—This series consisted of an experiment in which two groups
of oysters were exposed for one week to contamination with Kepone from
sediments in suspension and subsequently depurated. One group received York
River water at ambient temperature (which at the beginning of the experiment
was 9.0°C) and the other received York River water which had been heated up
to 20-21°C. The total depuration period was 15.6 days. Oysters were sampled
-------
six days after initiation of depuration and again after another 9.6 days.
At the end of the one-week contamination period there was very little
difference in the Kepone concentration between the two groups of oysters,
0.34 vs. 0.36^<_g/g (Figure 11""). The mean temperature for that week in the
ambient-temperature tray was 11.0°C with a range of 9.0-13.8°C (Table 7). In
the tray receiving warm water "the mean was 21.1°C with a range of
10.8-23.5°C. The lower temperature in this range represents a temporary
malfunction of the heat exchanger system.
* Figure 11 also includes contamination and depuration data for experiments
conducted between 12 January and 5 February 1979.
<•- - ^- —
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, ^^~ " "=~" -.'-
-^-" "^ _ ^.v-,-.-'—'?
-i<
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\*c*\d^
-------
There was marked difference between the two groups of oysters during the
first week of depuration (Figure 11, Table 8). Oysters depurating in 23°C
water showed a 69% reduction in their concentration of Kepone. Those
depurating in 13°C showed only a 9% reduction in Kepone concentration.
During the second week of depuration, however, the reduction rate of
Kepone was greater in the oysters held in 15°C water than in those held in
24°C Vater (90% vs. 73%), so that at the end of the two-week depuration
period, the Kepone concentration was the same in the two groups of oysters.
Seventh series--An additional series of experiments was conducted
between 12 January and 15 February 1979 as part of a separate study. The
data are included here because they are pertinent to the subjects covered in
this report. They are summarized in Table 9 and Figure 11.
Oysters received a very dilute suspension of sediments contaminated with
Kepone (mean hourly concentration = 0.12^/:g/l) for 10 days and were
subsequently allowed to depurate at two different temperatures (mean, 10°C
and 16°C). At the end of the contamination period the concentration of
Kepone in the oysters was 0.05//vg/g. Considering the fairly low level of
Kepone in the oysters at the start of depuration, the rate of depuration was
slow at both temperatures. It was significantly slower than what was
observed in the sixth series when the contamination level at start of
depuration was around 0.35/^g/g.
[ Cnx-m.
Following the first week of depuration.oysters held in 16°C water showed > )
a residual concentration of Kepone lower than that in oysters depurated in
10°C water. After two weeks of depuration the relationship between the
-------
Kepone residue in the two groups was similar to that observed after the first
week. Oysters in the warmer (16°C) water had half as much Kepone as those in
the colder (10°C) water.
Kepone in oyster meat vs. Kepone in sediment suspensions—Figure 9 of
the annual report for 1976-77 (Haven and Morales-Alamo, 1977) showed the
regression of Kepone concentration in oyster meats on the Kepone
concentration in the sediment suspensions flowing over the oysters in
laboratory trays. That regression analysis has been updated in the present
report by inclusion of additional data from experiments conducted after
September 1977. Many of the new data correspond to concentrations of Kepone
higher than 0.15//g/l (ppb) in the sediment suspensions. The correlation
coefficient did not change much (0.810 vs. 0.781) with inclusion of the
additional data (Figure 12).
The regression line shows a positive correlation between the
concentration of Kepone in oysters and that in the sediment suspensions.
However, the slope of the line indicates a sharp decrease in the ratio of
Kepone in oysters (in/<:g/g or ppm) to Kepone in the sediment suspension
(in/,'g/l or ppb) as the latter increases. This relationship is better
illustrated in Figure 13 where data extracted from the regression line in
Figure 12 are plotted in terms of the concentration factor against Kepone in
the sediment suspension. There is a sharp drop in concentration factor
between concentrations of 0.001 and 0.05/ig/l in the suspension. The
decrease is much slower at concentrations higher than 0.1
Kepone in oyster meats vs. Kepone in sediment particles — Al 1
concentration factors presented so far have been based on the concentration
-------
of Kepone in the suspensions of sediments flowing over the experimental
animals. The quantity of Kepone per unit volume of suspension was determined
by the quantity of Kepone adsorbed to sediment particles as well as by the
extent to which the sediments were diluted by the water flow volume used to
transport them over the animals. It was, therefore, considered advisable to
compare the Kepone in oysters with the Kepone in the sediment used to prepare
the suspensions after they were dried (Table 10).
We found no evidence of a correlation between the Kepone concentration
in oyster meats and the Kepone concentration on the sediment particles
(Figure 14). Similarly, there was a lack of correlation between the
concentration factor based on the Kepone adsorbed on sediment particles and
the Kepone on the sediment particles (Figure 15). Hence, our data fail to
relate the concentration of Kepone in the sediments with that in oyster
meats, even though those sediments are the source of all the Kepone in the
sediment suspension flowing over the oysters.
However, our data show that the Kepone concentration in oyster meats was
correlated with that in the sediment suspension given as mass of Kepone per
volume of water (Figure 12). Examination of the data on Table 10 shows that
when the same or similar concentration of Kepone in dry sediments is diluted
by different factors, resulting in different concentrations in suspension,
the Kepone in oysters is also correspondingly different. For example, on
week 4 of the period 24 February-27 March 1977 the Kepone in dry sediments
was practically the same in the three experiments conducted (1.03-1.05) but
they were diluted to three different levels. The result was that oysters
receiving the more dilute suspension had a lower concentration of Kepone in
-------
their meats than those receiving the less dilute suspensions. Observations
made for all other weekly periods were similar to the above concentration in
the oysters varied in direct relation with the extent to which the original
sediments were diluted and independently from the concentration in the
original dry sediments.
The concentration factor "biased on Kepone adsorbed on sediment particles
shows "that the Kepone taken up by oysters constitutes only a small fraction
of the Kepone associated with the sediment particles. In most instances,
Kepone in oysters was under 20% of that on the sediments and the maximum
accumulation in oysters was 27.5%.
Kepone in oyster biodeposits—Biodeposits collected from trays holding
oysters that were receiving contaminated sediments in suspension exhibited a
compartmentalization of Kepone relatively similar to that reported in the
1976-1977 annual report (Haven and Morales-Alamo, 1977). The concentration
of Kepone in feces was, in most cases, between one and nine times higher than
the concentration in pseudofeces (Table 11). In one exceptional case the
proportion was 88 to 1.
The data collected in 1976-1977 showed that the concentration in
pseudofeces and in sediments settling out by gravity were similar. In most
cases it was higher in the sediments than in the pseudofeces but not by a
great margin. The 1978-1979 data, however, showed sediments with a
concentration between two and seven times greater than in the pseudofeces
(Table 11).
-------
l\
Regression analysis shotted that there was a high correlation between the
concentration of Kepone in oyster feces and gravity-settling sediments and
the concentration in the sediment suspensions (expressed as the mean hourly
concentration for the weekly period immediately preceding collection of the
oyster sample). The correlation coeffic/Sints were 0.839 and 0.906, S C
pseudofeces and the concentration in the sediment suspensions was 0.685
(Figure 18).
Range of the concentration factors (based on Kepone mass per liter of
suspension) for feces was between 15,275 and 133,333 (Table 11). In
pseudofeces it ranged between 1,260 and 39,167. Concentration of Kepone in
gravity-settling sediments was between 7,897 and 8,828 times higher than that
in the sediment suspensions.
Oyster meats were analyzed for Kepone in only two of the five
experiments presented in Table 11. In those experiments the concentration
factor in oysters were 813 and 4,167. Mean temperature for each of the three
contamination periods were: 16-25 August, 29.2°C; 6-13 October, 20.7°C; and
13-20 October, 19.0'C.
The combined data on biodeposits for the years 1977 to 1979 are
presented here in relationship to the concentration of Kepone adsorbed on the
sediments used to prepare the suspensions flowing over oysters (Table 12).
The concentration factors (based on the Kepone associated with sediment
particles) ranged from 0.757 to 2.236 in feces and from 0.032 to 0.563 in
pseudofeces. The concentration in gravity-settling sediments was between
-------
0.217 and 0.903 times that in the original sediments used to prepare the
suspensions.
Translated into percentages, the concentration factors show that the
Kepone in the feces was between 62 and 224 percent of that found in the
original sediments. Likewise, Kepone in the pseudofeces was between 3 and 56
percent that in the original - sediments* while in the gravity-settling
sediments it was between 22 and 90 percent.
Regression analysis showed a positive correlation between Kepone in
feces and that in the original dry sediment (r = 0.932). The same was true
for pseudofeces (r = 0.709) and gravity-settling sediments (r = 0.915).
These correlations are similar to those found between feces, pseudofeces and
gravity-settling sediments and Kepone in the sediment suspensions.
Rangia cuneata—
Kepone in Rangia meats vs. Kepone in sediment suspensions—No laboratory
experiments were conducted with Rangia cuneata between October 1977 and
January 1979. The data collected in the laboratory between October 1976 and
October 1977 are used in the present report to examine certain relationships
not dealt with in the 1976-77 report.
The relationship between Kepone in the meats of Rangia clams and Kepone
in the sediment suspension flowing over them in laboratory trays is
illustrated by the data plotted in Figure 19. The data used appear in Tables
2 and 3 of our previous report (Haven and Morales-Alamo, 1977). A moderate
positive correlation of 0.614 was found. As was the case for oysters, the
ratio of Kepone in the animal meats to that in the sediment suspension
-------
decreased sharply as the latter increased.
This suggested that the concentration factor of Kepone for Rangia was
also negatively correlated to the Kepone in suspension. Figure 20
illustrates the relationship between these two parameters. The correlation
coefficient was negative but low. and the slope of the regression line was not
s
significantly different f ronr zero at P = 0 .05. although it was different from
/ .x^ V V >^ x
Bfmrt V XOiO/alLli
lkfr
f G
ui.i zero at P = 0.10. Due to
these low correlation coefficients no inferences will he made from these
data.
A plot of Kepone in Rangia against Kepone on the sediment particles
showed no correlation between the two (Figure 21; Table 13). Neither was
there any evidence of a relationship between the concentration factor in
Rangia (based on the Kepone adsorbed on the sediment particles) and the
Kepone on the particles (Figure 22; Table 13).
As was shown for oysters, the extent to which sediments containing a
specific concentration of Kepone are diluted in water will determine the
concentration of Kepone in Rangia clams receiving the sediment suspension.
Corbicula manilensis—
One contamination experiment was completed in the laboratory using the
Asiatic clam Corbicula manilensis between 6 October and 4 November 1977. The
Corbicula clams were obtained about 6.5 km upriver from Jordan Point in the
Qs
James River and, consequently, were found to be contaminated with Kepone. We
tried unsuccessfully to depurate them before start of the experiment. They
were placed in running freshwater from a ground well (Temp. = 17°C) with a
A
-------
supplementary supply of cornstarch and York River sediments in suspension.
They were active during the three weeks that they were held under depuration
conditions and mortalities were less than 3%. Although those conditions were
considered satisfactory for depuration, no reduction in Kepone was observed.
Therefore, the experiment was started with animals which already had
some Kepone in their tissues - (-CK 12^g/g) . The Corbicula in the control tray,
receiving a cornstarch suspension in ground well water, did not appear to
fj t&S JL lo/jse any Kepone during the four weeks of the experiment (Figure 23; Table
>• 14). Temperatures during the experiments ranged between 17.1 and 20.7°C
(Table 1).
The concentration of Kepone in the tissues of animals receiving sediment
suspensions with low Kepone concentrations (ranging between 0.05 and 0.08
/Xg/1) did not show much change during the first three weeks of the experiment.
There was an increase to 0.19 g/g at the end of the fourth week.
The clams receiving a high concentration of Kepone in the sediment
suspensions (mean ranging between 0.18 and 0.25/^g/l) showed very little
change from the original level during the first three weeks. During the
fourth week, there was an increase to O.SS^g/g. The two samples of oysters
analyzed at the end of that period had very different concentrations (0.084
vs. O.SS^g/g, Table 14) and the lower value was ignored because it appeared
unrealistically low.
Height of the clams used in this experiment ranged between 3 and 5 cm.
-------
it
Mu1inia lateral is —
A single experiment was conducted with the clam Mulinia lateralis (a
common bivalve in the lower James River estuary) between August 29 and
September 19, 1978. The clams were exposed to sediment suspensions
contaminated with Kepone for 16 days and subsequently depurated in
uncontaminated York River water"" for a little over six days.
The sediments used to prepare the suspensions were collected inside
Bailey Creek at Hopewell and had a high concentration of Kepone (around 14
.g/g). Consequently; the diluted suspensions flowing over the Mulinia were
much higher than any used in previous experiments of this type, 0.75 and 1.14
(Table 12).
After the first week of contamination the Mulinia meats showed a mean
Kepone concentration of 0.50/cg/g (Table 15; Figure 24). At the end of the
second weekly period the mean concentration in the meats was 0.54xu:g/g.
These values represented concentration factors of 537 and 529, respectively.
The clams left in the tray after the second week samples were taken out
were depurated in uncontaminated York River water for another six days. At
the end of that period, analysis of two samples of the clams showed
concentrations of 0.03 and 0.02//<;g/g, respectively, a reduction of 95% in
their Kepone content.
Mean height of the darns used and water temperature and salinity during
this experiment appear in Table 16.
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Ifr
Field Uptake Experiments
Two groups of experiments under field conditions in the James River were
conducted with oysters and Rangia to gather data for comparison with the
information collected in the laboratory. In one group, uncontaminated
animals were held in trays receiving contaminated water pumped from creek
tributaries of the James (Deep;-Creek and Skiffes Creek). These experiments
were basically identical to those conducted in the laboratory because the
animals were held in the same type of trays and received similar water flows.
the second group of experiments was conducted in the James River proper by
s
holding uncontaminated oysters in large wire trays sitting on the river
bottom. These experiments were designed to determine the time period it took
oysters and Rangia to reach a steady state in their natural habitat, the
level of contamination attained under natural conditions and as a check on
results obtained in the laboratory.
Uptake by Oysters at Deep Creek—
Five experiments were completed in trays receiving water pumped from
near the bottom of Deep Creek at Menchville (Table 17). Three of them
involved exposure periods of 7-8 days. Two others involved exposure periods
of 15 and 22 days, respectively.
During the period that these experiments were conducted, 12 July-4
August 1978, the concentration by weight of suspended sediments in the water,
determined from a composite sample for each of the three weekly periods
included, ranged between 25 and 29 mg/1. Corresponding Kepone concentrations
in the sediment collected by centrifugation for the same periods ranged
-------
between-iDt.06 and O.OSy^g/l. Kepone concentration in the sediment suspensions
flowing-,tpver the oysters, computed from those data, ranged between 0.001 and
0.002/i-g/d. They appear in parentheses over the corresponding values for
Kepone in oyster meats on Figure 25.
Oysters exposed to the above sediment suspensions for weekly intervals
showed mean Kepone concentrations in their tissues ranging between 0.05 and
0.065^x^/1. The concentration factor based on the concentration of Kepone in
the sed.rment suspensions ranged between 27,000 and 43,000 (Table 17).
Oystters exposed to Deep Creek water for two weeks (12-28 July) had a
slight Ly/i higher mean Kepone concentration than those exposed for one week
(Figure,52,5) . The concentration factor was 55,555. Oysters exposed for three
weeks CKt July-4 August), however, showed concentrations of Kepone similar to
those found in oysters exposed for one/week. Their concentration factor was
28,261. orThe relationship between the mean concentration of Kepone in the
sedimeat:-suspensions for the weekly period before oysters were analyzed and
the Keptfcne concentration in oyster meats agrees very well with the data
collect-ad in the laboratory. They fit the regression line in Figure 12
adequately. Thus, these field data support the laboratory finding of a
relationship between Kepone in oysters and the concentration in suspension
during the week prior to sampling.
Table 18 presents the concentration factor based on the Kepone
associa-tted with the sediment particles, disregarding their dilution in water,
for thersame groups of oysters that appear in Table 17. These factors
indicate that the Kepone in oyster meats was between 71 and 108 percent of
that fcsuad on the sediment particles. These figures are much higher than
-------
those recorded in the laboratory experiments, which only ranged between 2 and
27%.
The concentration of Kepone in the deposits that accumulated in the
trays was similar in all trays for any one weekly period, with one exception
(Table 19). The concentration in Tray #1, which held oysters, was much
greater than in the other two'trays sampled at the end of the 12-19 July
period. It was also much greater than that found for any other tray in the
following two weekly periods.
The weight of the biodeposits and sediments that collected in the trays
holding oysters was between 83 and 87 percent greater than the deposits that
collected in the control trays without oysters. The difference was observed
for all three weekly periods.
Water temperature and salinity measurements made once a day at the Deep
Creek experimental site showed the following ranges for each of the three
weekly periods: 12-19 July, 25.0-27.5°C and 11.89-12.95 °/oo; 19-28 July,
27.0-29.5°C and 11.22-12.89 °/oo; 28 July-4 August, 28.2-29.8°C and
11.08-12.43 °/oo (Table 20).
Uptake by Rangia Clams at Skiffes Creek--
Six experiments were completed in which Rangia cuneata clams in plastic
trays received water pumped up from near the bottom at Skiffes Creek (Fort
Eustis). Exposure period in four of the experiments ranged between 5.1 and
10.0 days. Duration of exposure in the other two was 17.0 and 22.1 days.
-------
r » IT*"
\ In experiments of 5 to 10 days duration, the concentration of sediments \
I suspended in the water flowing over the animals ranged between 37 and 46 mg/1
(Table 21). The concentration of Kepone in the suspended sediments ranged
between 0.04 and 0.15/cg/g. The combination of these two measurements in
each experiment resulted in a range of concentrations of Kepone in the
sediment suspensions between 0.001 and 0.007/,/g/l (Figure 25).
Rangia held in trays for 17 days between June 2 and 19 had a mean Kepone
concentration of 0.10^g/g at the end of that period. This concentration is
not too different from that observed for the clams held in trays only during
the last 10 days of that period (9-19 June"; Expt. No. 3, Table 21). During
those ten days both groups of clams were exposed to the same concentration of
Kepone in the sediment suspension (0.007^/^/1) and concentration factors for
both groups were based on that value. Clams exposed for 10 days showed a
concentration factor of 12,857 and those exposed for 17 days showed a factor
of 15,000.
Clams held in trays for about three weeks (2-26 June) had a mean Kepone
concentration of O.ll^g/g in their tissues. That concentration was only
slightly higher than the concentration in clams held in trays for the last
five days of the same period (20-26 June; Expt. No. 4, Table 21).
Concentration factor for the clams exposed for 22 days was 36,667 while that
for clams exposed for five days was 26,667.
Table 18 presents the concentration factor based on the Kepone
associated with the sediment particles, disregarding their dilution in water,
for the same group of darns that appear on Table 21. These concentration
factors show that the Kepone in the clams was between 60 and 150 percent that
-------
found on the sediment particles. As in the case of oysters, these figures
are much higher than those observed in laboratory experiments.
Both water temperatures and salinity increased progressively during the
period of time included by these studies (Table 16). Single daily
measurements at Skiffes Creek showed the following ranges, respectively. for C
each of the time periods included in the studies: 17-25 May. 19.7-23.0°C and
0.14-0.55 o/oo; 2-9 June, 24.4-25.3°C and 0.64-1.20 o/oo; 9-19 june)
24.0-26.0°C and 1.07-3.40 °/oo; 20-26 June, 25.7-27.2°C and 3.19-3.74 °/0o •
The increases in temperature and salinity did not appear to affect the
results obtained.
Deposits that accumulated in the trays during each of the experimental
periods did not differ much in Kepone concentration (Table 22).
Concentrations recorded in the control trays without clams (Tray #4) were not
different from those recorded in trays holding clams, except that during the
week of 17-25 May-. Kepone in the tray without clams was higher than in the
tray with clams.
Weight of the material that accumulated in the trays was greater in
trays holding clams than in the control tray without clams. In most cases
the difference was greater than or approached 50%.
Tray Experiments in the James River—
Oysters— Salinity at the three stations selected for field experiments
was low in May (Table 23). Therefore, no oysters were set out until the
first week of June. Salinity at Deep Water Shoal continued low through June
and most of July. For that reason, most of the data on uptake by oysters was
-------
collected at Wreck Shoal and Point of Shoals (Figure 2).
The data from oysters held in bottom trays at Wreck Shoal showed no
evidence that length of exposure beyond the first week affected the
concentration of Kepone in the oyster meats (Table 24; Figure 26). Oysters
exposed for 52 days had a mean concentration of Kepone very similar to that
in oysters exposed for time per-iods of four, 14 or 24 days (Expt. No. 1, 5
June-27 July). Individual values in oyster samples for each of the six
exposure periods ranged between 0.06 and 0.12/xg/g. These extremes were not
correlated with length of exposure. Mean concentration of Kepone in two
other groups of oysters exposed for seven days each on successive weeks (27
July-10 August) was 0.09 and O.lly^g/g.
There was a similar lack of correlation between Kepone in oyster meats
and length of exposure after the first week at Point of Shoals.
Concentration of Kepone in individual samples of oysters ranged between 0.10
and O.n^g/g (Table 25; Figure 26). The level reached after 34 days did not
differ greatly from that attained after 10 days. Two other groups of oysters
held in trays at Point of Shoals for seven days each on successive weeks
(following the end of the 34-day experiment mentioned in the preceding
paragraph) showed a mean concentration of 0.19 and 0.12^^/g, respectively.
The mean concentration of Kepone was similar in two groups of oysters
exposed in bottom trays at Deep Water Shoal for equal time periods of seven
days on two successive weeks (27 July-3 August and 3 August-10 August; Table
26, Figure 26) .
Ten pairs of oyster samples collected from the trays and from the
-------
natural bottom population on the same date at the same stations were compared
by regression analysis (Table 27). The correlation coefficient for the 10
i^ was 0.764 (Figure 27).
A t-test comparison of the means for individual tray and bottom oyster
samples collected on the same date at the same station showed no evidence of
a difference between them at'Wreck Shoal and Point of Shoals (Figure 28).
Values of the individual samples used appear in Tables 24 and 25. The paried
samples collected at Point of Shoals on August 3 (Table 25) were not included
in the comparison because of the great difference between them (79%). "t"
value for the Wreck Shoal data was 0.568 ('d . f . = 17) and for the Point of
Shoals data, it was 0.146 (d.f. = 13). No such comparison was made for Deep
Water Shoal because of the few data available.
The above comparison indicates that the data for tray and bottom oysters
are comparable and represent the same population of oysters. The variations
found may be explained as arising from the natural variations within the
popul at ion.
Sediments at oyster tray stations — <^ — s
- -•« }
s
Kepone concentration in sediments collected in bottom sediment traps
ranged between 0.02 and 0 .08^
-------
collected at Wreck Shoal because the large expanse and thickness of the
oyster beds did not permit our dredge to pick up any in the immediate
vicinity of our tray stations. No correlation was found between the Kepone
in tray or bottom oysters with Kepone in either the bottom sediments or the
sediments collected in the bottom trays.
Concentration Factors for Oysters—Concentration factors based on the
Kepone concentration in the sediment suspensions over the oysters on the
bottom were not computed in these tray studies. We did not have the data
required to obtain a good estimate of the suspended load available to the
oysters.
Data for the concentration of Kepone on sediment particles collected in
the vicinity of the experimental trays are available. We can, therefore,
compute the concentration factors based on the Kepone associated with those
sediment particles, without regard to their dilution in the water. Table 28
presents the computed concentration factors.
Most of the concentration factors were greater than one. The maximum
for computations based on the Kepone in trap sediments was 5.375 and the mean
was 2.745. The maximum, based on the Kepone in bottom sediments, was 12.500
and the mean was 5.043.
Rangia—As was the case with oysters, Kepone concentration in the
tissues of Rangia cuneata was not associated with the length of the exposure
period.
Concentration factors for Rangia—No data were available on the
concentration of suspended solids over Deep Water Shoal during these studies.
-------
Therefore, a concentration factor based on Kepone in the sediment suspension
over the clams in the wire tray could not be estimated.
Concentration factors based on the Kepone associated with sediment
particles, without regard to their dilution in the water, for the Rangia held
in a wire bag at Deep Water Shoal appear in Table 28. All values were
greater than one. The average '"f or factors based on trap sediments was 1.631
with a range between 1.000 and 2.125. The mean for three factors based on
bottom sediments was 2.903 with a range between 1.375 and 5.500.
Size analysis of trap sediments — Ten samples of the sediments which
accumulated in sediment traps at the three tray stations were analyzed for
size distribution. Results appear on Table 30 and Figure 30.
Most of the sediments collected in the traps at all three stations fell
in the 8-16 and 16-32 size fractions. With one exception (Wreck Shoal, 3
August) the individual fractions smaller than 4/<^- were significantly lower in
weight than the fractions between 8 and 32/^_ and those >32 .
Combination of the fractions into three major ones, <8/^, 8-34^ and
showed that the 8-32/x- fraction is the dominant one in every case (Table 31).
The other two fractions were similar in most instances.
-------
SECTION 4
DISCUSSION
Study of uptake of Kepone from sediments in suspension by oysters and
other filter-feeding organisms is important to the understanding of the
eventual distribution of Kepone in the James River estuary as well as its
effect on populations of these animals exposed to it. Information thus
obtained can be used to compare the relative importance of Kepone adsorbed on
sediments and Kepone in solution in the contamination of this important
segment of the James River fauna.
Our studies were directed towards establishment of the extent to which
oysters and other bivalves are able to pick up Kepone from contaminated
sediments flowing over them. A basic assumption in our laboratory
experiments was that whatever amount of Kepone oysters would pick up would
derive from Kepone adsorbed onto the organic and inorganic particulate matter
in the prepared suspensions. This assumption was based primarily on the fact
that the carrying agent for the contaminated sediments (York River water)
would be free of Kepone initially and would not be expected to strip Kepone
from the sediments to any significant extent.
The above assumption is supported by the statement of Schneider and
Dawson (1978). that in the James River, sediments represent the massive source
-------
of Kepone available to the biota. Indications are that the concentrations of
Kepone in solution in the James River are extremely low. In spite of the
assumption made, the possibility that some Kepone in solution is taken up by
oysters and other filter feeders is not completely disregarded.
The major observations made from the data collected during these studies
1. Oysters and Rangia clams attain a steady state for concentration of
Kepone in their tissues in at least one week.
2. Depuration of oysters in the laboratory to levels below the FDA
action limit was accomplished in one week but some Kepone was still
present after three weeks.
3. The concentration of Kepone in the tissues of oysters and Rangia
increases as the concentration of Kepone in the sediment suspension
also increases.
4. The concentration factor based on the concentration of Kepone in the
sediment suspension decreases as the concentration of Kepone in the
sediment suspension increases.
5. There was no relationship between the concentration of Kepone in the
sediments used to prepare the contaminant suspensions and the Kepone
concentration in oysters or between the concentration factor based
on the Kepone in the dry sediments and that in oysters.
6. Although many of the values for the concentration factor based on
Kepone per unit volume of the sediment suspension were very high,
-------
f
the actual concentration of Kepone in laboratory oysters was between
2 and 28% of that in the dry sediments used to prepare the
suspensions, depending on the concentration of the sediment
particles in the suspension. In Deep Creek studies, however, Kepone
in oysters was between 71 and 108% that in the sediment particles.
7. Oyster feces contained much higher concentrations of Kepone than
pseudofeces or sediments settling out by gravity in the laboratory
experimental trays.
8. The weight of material deposited in t.r ays (ho Id ing oysters or Rangia,
/ ^ --
and receiving water pumped from two tributary creeks of the James
River), exceeded by a wide margin that which deposited by gravity
alone in trays without animals.
9. Data collected in field experiments confirmed results obtained in
laboratory experiments.
10. There are indications that part of the Kepone in the tissues of
oysters may derive from Kepone in solution in the James River.
These and other observations are discussed below.
Curves for concentration of Kepone in oysters plotted against exposure
time suggest that oysters reach a steady state in the concentration of Kepone
in their tissues within one week. ) Beyond the first week there is no furthog-
increase in concentration in the sediment suspensions remains fairly
constant. This was shown by the normalized curves presented in the 1976-1977
annual report (Haven and Morales-Alamo, 1977). Figures 6 and 18 in the
present report also substantiate this conclusion. The data of Bahner et al .
-------
um
(1977) for oysters exposed to dissolved Kepone showed they attain equilibri
within 8 to 17 days.
Two other sets of data support the conclusion that a steady state is
reached within one week. Introduction of uncontaminated oysters into trays
holding oysters which had already been exposed to contamination for the
preceding one to three weeks resulted in both groups of oysters having
similar concentrations of Kepone at the end of one week. Those results.and
the excellent correlation found between the concentration in oysters and the
mean hourly concentration in the sediment suspensions for the week preceding
s ampling^ show that it is the concentration in the suspension during the week
before sampling that determines the concentration in the oysters. Thus, the
steady state for concentration in oysters must be reached within one week.
The steady state seems to be achieved within one week regardless of the
concentration in the sediment suspension. The level at which the steady
state plateau occurs will increase but it will still be attained by the end
of one week.J>As concentration in the sediment suspension increases, the
magnitude of the increase in the steady state level becomes progressively
smaller, in agreement with the relationship illustrated in Figure 12 where
the ratio between Kepone in oyster to Kepone in the sediment suspension
decreases as the latter increases.\ The experiments conducted at Deep Creek
in which oysters in plastic trays received water pumped from the creek
substantiated the conclusion based on laboratory studies that the steady
state is attained in one week. They also showed that the concentration of
Kepone present in suspension during the week previous to sampling determines
the concentration of oysters. The data collected in studies in which oysters
-------
were held in wire trays on the bottom of the Janes River also corroborated
the observations made in the laboratory and at the Deep Creek pier concerning
the attainment by oysters of the steady state within one week and the
determinant role of the Kepone concentration in sediment suspensions on the
week before sampling.
Attainment of a steady state in one week (or possibly sooner) implies
that oysters are capable of making quick adjustments to changes in the level
of Kepone in suspension and that the effects of short term disturbances that
would increase the levels of Kepone in suspension temporarily would dissipate
quickly as the levels in suspension decrease. The quick adjustment to levels
in suspension are evident when oysters are allowed to depurate in
uiicontaminated water-
Bahner et al . (1977) found that oysters contaminated in Kepone solutions
in the laboratory depurated themselves of Kepone to non-detectable levels in
7 to 20 days.) Our laboratory studies showed that oysters gijgi lose most of X — -Jl
their Kepone in one week but t-kaJ: — ilT'TTD'ut-d take a much longer period of time
fjc«r"tfeem to rid themselves of all their Kepone. \ The rate of depuration,
£
however, wt«4d"" dependjon water temperature.
Data collected separately by one of us (Haven, unpublished data) showed
that contaminated oysters held in trays suspended from a pier in the York
River at Gloucester Point did not depurate themselves of Kepone at
temperatures under 8°C (Table 32, Figure 32). Oysters from the James River,
with a Kepone concentration of 0.19 Mg/g, were placed in the York River trays
on 22 January 1976 when the water temperature was 2.5°C. Samples of the
oysters analyzed one month later, on 18 February, showed that the oysters
-------
retained practically all of the original Xepone. During that period of 26
days the water temperature exceeded 8°C only during the last 24 hours and
then only for half that time.
During the following week (18-26 February), however, the oysters lost
53% of their Kepone at water temperatures ranging between 7.4 and 10.6°C.
Eighty-two percent of that time water temperature was under 9.0°C and it was
« ^
under 8°C only 16 % of the time. Between 26 February and 12 March (15 days),
when the water temperature was mostly between 9 and 13°C, the oysters reduced
their Kepone by 75%. The total reduction between 18 February and 12 March
(23 days) was 88%.
These results show that oysters are separately able to eliminate Kepone
at temperatures as low as 8°C and that they are definitely active in
depuration of Kepone at 9°C. In the same study, however, oysters held in
laboratory trays in water whose temperature had been raised to 15°C depurated
much faster during the period 18-26 February than those held at ambient
temperatures in pier trays (Figure 32). These data and other data presented
in this report indicate that oysters are more efficient in depurating
themselves of Kepone at temperatures of 15°C and higher, but that they will s
continue to eliminate Kepone at lower temepratures until the limiting
temperature of 8°C is reached. They also showed that there was very little
further reduction in Kepone between 0 .01-0 .02 //g/g regardless of how warm the
water was.
Bender et al. (1977) have shown that it takes oysters much longer to
depurate at the lower winter temperatures than during the summer.
Nevertheless, there are indications that oysters lose-Kepone throughout the
-------
7
winter months as shown in Figure 3 of the same paper. The moving average
decreases steadily between December 1975 and April 1976 and between December
1976 and March 1977. There is a similarity between that decline in the
residue levels of Kepone in oysters during the winter and separate
observations made on the depuration of coliform bacteria by oysters in the
lower Chesapeake Bay ./7Haven ej^ _al^- (1977) found that when water temperatures
are lowered, there is an inhibition of the pumping and filtration activity in
oysters,^ accompanied by an inhibition of accumulation of coliform bacteria.
^
C
but apparently not an inhibition of elimination of inactivation of the same
bacteria resulting in a net loss of coliform b-acteria from the shellfish
during that period.^The processes involved in elimination of bacteria and of
Kepone by the oysters may be different, but it appears that temperatures which > C«r»*•**•-'
cause oysters to become almost completely inactive physiologically do not
prevent the loss of both of these contaminants.
Our data also suggest that the rate at which oysters depurate iCepone is
not a constant for the animal. Support for this concentration is provided by
the depuration rates shown in Figure 8 for oysters that had been exposed to
contamination for three weeks and subsequently allowed to depurate for one
week. Even though the difference in Kepone levels at the start of depuration
was large (0.25 vs. 0.13 Mg/g), depuration efficiency was almost identical in
both groups of oysters (77 and 76 percent; Table 40y. The rate of elimination SiA/oU*3*X-
and/or accumulation of Kepone by the oyster may vary according to exchange
equilibria between the sediment suspension and the oyster's tissue fluids as
was proposed by Hamelink et al^. (1971).
-------
The laboratory data collected during the studies reported here showed a
high positive correlation between the concentration of Kepone in oysters and
that in the sediment suspensions used to contaminate them. On the other
hand, no correlation was evident between the Kepone concentration in oysters
and that in the dry sediments used to prepare the contaminant suspensions.
It is thus evident that the extent to which the contaminated particles are
diluted when suspended in water will be as important in determining the level
of contamination in oysters as would be the concentration of Kepone in the
sediments making up the suspension.
Although the Kepone adsorbed on the sediments used to prepare the
suspensions was the source of all the Kepone in the suspensions, it could not
be related to the concentration in the oysters because the extent to which
they were diluted in York River water apparently affected the rate of uptake
by oysters. The data on Table 10 show that as the dilution of the original
dry sediments increased the concentration in oysters decreased. The less
Kepone available to the oyster in any given time period, the less it will
take up, because the animal maintains a continuous flow of the material
through the gut with continuous ingestion and defecation. In such a process,
time becomes a significant factor and since dilution affects the quantity of
sediments and, consequently, the quantity of Keponey that the oyster can
ingest and accumulate in its gut in a given time interval, it also affects
the quantities of Kepone it will take up into its tissues.
The positive correlation between Kepone in oysters and Kepone in a
sediment suspension will probably cease to exist only at the point where the
-------
concentration of sediments (or total solids) in suspension is so high that it
will cause the oyster to cease pumping.
The positive correlation cited above justifies the use of a
concentration factor for Kepone in oysters and other filter feeding bivalves
based on the concentration of Kepone per unit volume of the sediment
suspension. It is also justified because, as was stated earlier, this
concentration factor is analogous to the bioconcentration factor of other
investigators.
Oysters concentrated Kepone by factors ranging between 1,000 and 55,000
times that found in a unit volume of suspension. The highest concentration
factor, computed for field data from Deep Creek, was related to the lowest
concentrations of Kepone in the suspensions. As shown in Figure 13, there is
a negative relationship between this concentration factor and the
concentration of Kepone in the sediment suspensions with the sharpest decline
in the concentration factor occurring between concentrations of 0.001 and
0.05y^g/1 in the sediment suspension. The difference between the
concentration factor at a concentration of 0.001/,'g/l in suspension and that
at a concentration of O.Olpg/1 is 89%. Between concentrations of 0.01 and
0.05 /Ig/1 , the difference in concentration factor is 71%, while between 0.05
and 0.1 /*'g/l it is only 31%. At concentrations in suspension higher than
0.1 tig/I the difference between concentration factors for successive
/
increments of 0.1 decreases at a much slower rate. It would appear that
oysters are most efficient in concentration of Kepone from sediment
suspensions when the sediment suspensions are extremely dilute. This is
paradoxical and requires an explanation.
-------
1"
It could be that the oyster ingests most of the particles (and Kepone)
it is able to accommodate in its gut (and body tissues) at a very low
concentration of sediments (and Kepone) in suspension and relatively very
little more Kepone is picked up from suspension as the concentration in the
suspension increases beyond that point. However, this possiblity is negated
by the following computations made _using values extracted from the regression
line in Figure 12. At a Kepone concentration of 0.001 /-(g/l in suspension
oyster meats would have 0.072/'g/g of Kepone. Increasing the concentration
by 100 times to 0.1 //g/1, doubles the Kepone in the meats to 0.16/;'g/g. To
double the Kepone in the meats once again from, that point we only have to
increase the Kepone in the sediment suspension by a factor of three to
0.3 ^'g/g, resulting in 0.33 /.'g/g of Kepone in the meats. The Kepone in the
I ''
meats can be nearly doubled again to 0.60/?g/g by inreasing the concentration
/ ' "
in suspension to 0.5/^g/g, an increase by a factor of only 1.7.
Therefore, an increase in Kepone in suspension by a factor of 1.7
between 0.3 and 0.5 /'.g/l accomplishes the same rate of increase in Kepone in
the oyster meats that required an increase by a factor of 100 at the lower
concentrations in suspension of 0.001 and 0.1 /(g/1. Obviously, the oyster is
still capable of ingesting and assimilating significant amounts of Kepone at
the higher concentrations in suspension included in our data.
Some other explanation is required for the reduction in concentration
factor as the concentration in suspension increases. It could have resulted
from an increase in elimination of Kepone at the higher, exposure
concentrations as was suggested for fish by Mayer (1976). It could also be
an indication of a breakdown in the mechanisms that account for accumulation
-------
of Kepone in the oysters, as the concentration in the suspensions increases,
due to toxic effects on some physiological process involved in uptake or
elimination as suggested by Hamelink (1977).
However, it is interesting to note that the reduction appears to be
related to the fact that the regression line in Figure 12 intersects the
vertical (y) axis above the zero point (at a Kepone value of 0.072.('g/g in
oyster meats). Consequently, any reduction in the value for Kepone in the
sediment suspension below 0.01 /''g/1 (or even below 0.1 /'g/g) results in a
/ /
very large increase in the concentration factor because the resultant
decrease in the value for Kepone in the oyster meats is extremely small. The
fact that the regression line crosses the y-axis where it does may be
considered an artifact of our computations. However, the field data
collected at Deep Creek fit the regression line in Figure 12 adequately and
provide/ supportive evidence that the line is a good representation of the
true relationship between the two parameters. Consequently, the regression
line shows oysters with Kepone in their tissues, as much as 0.07/'vg/g, even
/
when apparently there is no Kepone in the sediments in suspension, since we
assumed that all Kepone available was adsorbed on particulate matter. We
interpret this to mean that oysters are obtaining Kepone from a source other
than the particulate matter in suspension. That source is likely to be
Kepone in solution in the water. This matter will be discussed further
b e 1 ow.
We found no correlation between the Kepone concentration in the
sediments used to prepare the contaminant suspensions (labeled "dry
sediments" in figures and tables) and the concentration of Kepone in oyster
-------
meats. Neither was there a correlation evident between the concentration of
Kepone in oyster meats and the concentration factor based on the Kepone
concentration in the dry sediments. This was so because the concentration of
the sediment particles and of the associated Kepone available to the oysters
was affected by the extent to which the sediments were diluted in river water
before flowing over the oysters. Sediments having the same concentration of
Kepone when analyzed dry resulted in different concentrations in the oyster
meats when diluted to different concentrations in suspension. Examples of
this effect are found in Table 10, particularly for the period 13 May-19 June
1977.
Consequently, the concentration in suspension of particles (living or
dead) carrying a contaminant should be taken into account in studies to
determine bioaccumulation factors as usually defined in other current
investigations. The concentration of the prey animal in the experimental
container will have a bearing on how much of the compound the predator will
accumulate in its tissues, since a higher concentration of the prey animals
will enhance their capture by the predator-
There was also a lack of correlation between Kepone in the sediments
collected in sediment traps and that in oysters held in trays at the bottom
of the James River or in those collected from the natural oyster beds.
Correlation coefficient for Wreck Shoal was 0.205 and for Point of Shoals it
was 0.329. Lack of a correlation could be due to the fact that the extent to
which these sediments are diluted in suspension is not being taken into
account.
Although the concentration factor based on the Kepone concentration in
the dry sediments was not correlated to the Kepone in the oyster meats.it T
-------
A
provides information that contrasts markedly with that obtained in the
laboratory and which could be useful in establishing the main source of
Kepone for oysters and other filter feeders. Kepone concentration in the
meats of oysters approached or exceeded that found in the dry sediments
passing over them in suspension at Deep Creek. In the laboratory studies,
Kepone in the meats was usually no greater than 20% of that found in the
sediment particles.
It appears that oysters in the field were able to extract Kepone from
the suspension more efficiently than those in the laboratory experiments.in ?
spite of the fact that the sediments used in the laboratory experiments had a
much higher concentration of Kepone when analyzed dry than those collected
from the Deep Creek water»and that the concentration in suspension was also
much higher in the laboratory studies. Once again the possibility appears
that some of the Kepone being accumulated by oysters, especially those in the
field, may come from solution.
The process of biodeposition by oysters and other filter feeders has
been suggested as an important element in estuarine sedimentary processes
(Haven and Morales-Alamo, 1966a). It would likewise be expected to play an
important role in the distribution of Kepone in the James River and for that
reason we conducted several experiments in which Kepone in biodeposits was
measured.
Oyster feces collected in those experiments contained much higher
concentrations of Kepone than pseudofeces or sediments settling out from
suspension by gravity. This difference is probably due to selective
-------
ingestion by oysters of particles associated with Kepone either because of
their small size or their chemical nature (organic). Between 80-95% of the
particles in oyster feces and pseudofeces are smaller than 3 or 4. and feces S tc**""
as well as sediments settling out by gravity contain higher levels of organic
carbon than pseudofeces (Haven and Morales-Alamo, 1966a, 1972). This
difference in organic carbon between pseudofeces and gravity-settling
sediments would explain why the latter had more Kepone than pseudofeces.
Pseudofeces are composed of particles rejected by oysters and, by selection,
they apparently are lower in the organic carbon than Kepone.
Although the sediments that settled out by gravity have not been
subjected to such a selection process, they have, however, settled out Sf ^A~v^'
selectively by size and/or mass. The larger and heavier particles that
settle out faster probably constitute the bulk of the sediments that settled
in the laboratory trays. These larger particles would also contain the least
amount of Kepone of all particles (Nichols and Trotman, 1977). Therefore,
their Kepone concentration would be lower than that in the original sediments
used to prepare the suspension. It would be lower than that in feces because
the two selective processes mentioned favor a higher concentration in feces.
The concentration of Kepone in feces, pseudofeces and in sediments
settling out by gravity was correlated to the concentration in the sediment
suspensions flowing over the animals. It was also correlated to the
concentration in the dry sediments used to prepare the suspensions. This is
a reflection of the manner in which oysters take food in from suspension.
The process is a near continuous one with particles being ingested and
passing through the gut with little interruption. At any one time interval
-------
the concentration of Kepone in biodeposits is going to be dependent on the
levels of Kepone in the sediment suspension and in the sediment particles
during the same interval. However, the differential concentration in the
biodeposits and sediments show how the feeding method of the oyster makes the
animal very susceptible to contamination with Kepone and how the sorting
processes during feeding can affect^the distribution of Kepone in the bed
sediments around it.
Oysters appear to select for ingestion fine particles which are
generally associated with high organic contents. These are the type of
particles most likely to have Kepone adsorbed on their surface.
Consequently, the feces produced by the oysters will reflect the effect of
that selective ingestion. Feces should contain higher concentration of
Kepone than pseudofeces and gravity-settling sediments and should concentrate
Kepone by fairly high factors. That is precisely what our data show. The
concentration in the feces ranged between 15,000 and 133,000 times (mean =
47,578) the concentration in the sediment suspensions and it ranged at
between 62 and 224 % (mean = 114.2%) of the concentration in the dry
sediments used to prepare the suspension. Not only will oyster feces be rich
in Kepone.but the quantities produced magnify their significance
considerably.
As measured during the experiments at Deep Creek, the quantities of
material that accumulated in the experimental trays holding oysters were much
greater than those that settled out by gravity in the trays without animals.
In those trays, between 83 and 87% of the material accumulated can be
attributed to biodeposition. These figures are almost identical to those
-------
found in earlier investigations (Haven and Morales-Alamo, 1966a). Therefore,
accumulation of these biodeposits proceeds at a faster rate than natural
deposition. Although the Kepone concentration in the material deposited in
the trays with animals was not different from that in the trays without
animals, the difference in quantity of the material accumulated would still
make biodeposition a more significant factor than in the deposition by
gravity in the accumulation of Kepone in bottom sediments. The lack of a
difference in the concentration of Kepone in the trays with animals and those
without animals is probably due to the fact that pseudofeces and
gravity-settling sediments would dilute the higher concentration of Kepone in
the feces and considerably reduce the value for the mixture of the three.
The magnitude of biodeposition was illustrated in a previous publication
(Haven and Morales-Alamo, 1966a) where it was estimated that one acre of
oysters 5 to 8 cm in size would deposit about 405 kg (dry weight) per week of
feces and pseudofeces with a possible maximum of 981 kg/week. Larger oysters
would produce even greater quantities.
It has been suggested several times above that oysters in the James
River may be obtaining some of the Kepone in their tissues directly from
solution in the water. This possibility appears real and deserves further
consideration. Schneider and Dawson (1978) have suggested that
bioconcentration (i.e., uptake directly from solution) is the mechanism which
is important in determining the amount of Kepone that will he picked up by
the biota of the James River. They acknowledge, however, that the amount of
Kepone available for bioconcentration is relatively small because it rarely
and other filter
ingest suspended sediments will have greater access to the
C\C pUIlC HV a. 1 J. clU X C i-U L U XUUXJUV- tMlU L Cl 1- J.WU 10 1. ^ XQ\_ ± v ^ j__y 01
trfT ) exceeds 0.008 /fg/U and that organisms such as oysters
V feeders which ingest suspended sediments will have grt
-------
11
Kepone available since sediments represent the major source of Kepone in the
James River.
Although the concentration of Kepone in solution in the James River is
very low, the potential for bioconcentration by oysters could be great enough
to magnify that concentration by a significant factor. This potential for
bioconcentration should not be ignored until proven to be otherwise.
Therefore, we will use our data and those of others to estimate the fraction
of the total Kepone concentrated by oysters that may derive from Kepone in
solution in the James River.
The concentrations in sediments collected in the traps set out in the
James River are comparable to the data collected by Onishi and Ecker (1978)
for suspended sediments at different tidal stages at Burwell Bay in the James
River. Concentration in the trap sediments ranged between 0.02 and
0.11 Mg/g. Concentration in the Burwell Bay suspended sediments ranged
between <0.012 to 0.143. Therefore, Kepone in the trap sediments appears to
be a close approximation of the Kepone in the suspended sediment load.
The concentration of Kepone in the sediments centrifuged from water
pumped out of Deep Creek fell within the above range, toward the higher end.
The similarity between these three sets of data indicates that they are a
good representation of the concentration of Kepone in the suspended sediments
of the James River in the area over the most productive oyster beds and will
be used in the computations that follow.
The mean concentration of Kepone for all oyster samples (tray and
bottom) collected at Wreck Shoal was 0.08 Mg/g. The mean for all oyster
-------
samples from Point of Shoals was 0. 13 i>,g/g. From the regression analysis
presented in Figure 12. we obtained the complementary regression line for
Kepone in sediment suspensions on Kepone in oysters. The line is not plotted
in Figure 12 (it is the complement of the line drawn in that figure) but its
equation is: X = 0.746Y - 0.019, where X is Kepone in sediment suspension
and Y is the Kepone in oysters-^SoS&ssRjy^the equation for the mean values jmO^
Kepone in the sediment suspensions that would correspond to those values in
Wreck Shoal it would be 0.04^/1 and at Point of Shoals it
is ion. their S CffY*^
would be 0.08
i
The mean concentration of Kepone in sediments collected in the bottle
traps at Wreck Shoal was 0.041 /'g/g. At Point of Shoals it was 0.036 /'g/g.
In order for sediments with that concentration of Kepone (0.04 /'g/g) to
attain a concentration of 0.04 and 0.08 ('g/l in suspension.
concentration by weight in the suspension would have to be between 1000 and
2000 mg/1. The concentration of suspended solids over the oyster-producing
areas of the James River are usually only a small fraction of that.
The concentration by weight of suspended solids over the principal
oyster rocks in the James River, between Horse Head Rock and Wreck Shoal
r\
Rock, range^on the average between 20 and 40 mg/1 (Nichols, 1972). At Deep
A
Water Shoal the average concentration by weight of solids is between 60 and
100 mg/1, this being the maximum turbidity area in the estuary and the inner
limit of salty water. Because of the low salinity in that region, oyster
production in Deep Water Shoal is low. Therefore, we will limit our
discussion to the Horse Head to Wreck Shoal area.
-------
Based on our data for sediments collected in traps and those centrifuged
from Deep Creek.we will assume that 0.08 //g/g is the highest concentration of
S i
Kepone to be found most frequently over the oyster beds. Then at
concentrations of 20-40 mg/1, the concentration of Kepone in the sediment
suspensions (particulate and dissolved) over the oysters would range between
0.002 and 0.003 /,-rg/l. These values are similar to the levels found in Deep
/" - ' •--
Creek suspended sediments and those predicted for particulate Kepone by
Onishi and Ecker (1978). Contamination level in oysters, corresponding to
those concentrations in sediment suspension, would be 0.07 /'g/p (as L dn*a/*
' )
extrapolated from the regression line in Figure 12). These values for
oysters and the sediment suspensions are very similar to what was actually
observed at Deep Creek and lend credibility to our computations.
The predicted value of 0.07 /6'g/g is also close to the mean obtained for
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Wreck Shoal oysters (0.08 /^g/g) , which we had indicated would require a
i
concentration of 0.04/^g/l in the sediment suspension for its attainment.
Hence, we have a very low concentration of Kepone in a sediment suspension
producing a concentration many times higher in the sediment suspension. We
see in this an indication that there may be another source contributing to
the uptake of Kepone by oysters. The computations that follow explore that
possibility further.
Bahner et al. (1977) exposed oysters to Kepone dissolved in water for 28
days at two different concentrations, 0.03 and 0.39//g/l. Oyster samples
t
analyzed at the end of that period showed Kepone concentrations of 0.21 and
2.2/g/g, respectively. Connecting those two points in a plot of the
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concentration of Kepone dissolved in water (in//g/l) against the
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corresponding concentration in oysters (in/Ag/g)jwe obtain the line shown i
Figure 31. This line will be used for other extrapolations in the following
paragraphs.
Assuming that the calculated distribution coefficient between sediments
and water is accurate for field levels of solids, Onishi and Ecker (1978)
predicted a concentration of dissolved Kepone averaging between 0.0048 and
0.008l/g/l for the James River. Values for the concentration of Kepone in
oysters corresponding to those two levels of dissolved Kepone were
extrapolated from Figures 31 and they were, respectively, 0.038 and 0.061
/.'g/g. Addition of these values to the one obtained earlier for oysters
(0.07/-;g/g) when the Kepone concentration in sediment suspensions was
/
estimated at 0.002-0.003 /'g/1 results in a total concentration in oysters
/
between 0.11 and 0.13 /--'g/g for the combined sources of Kepone.
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The range 0.10-0.13 /'g/g falls well within the values reported by Bender
et al. (1977) for James River oysters. The moving average of the monthly
samples for the years 1976 and 1977 shows extremes of 0.8 and 2.0/.-g/g with a
median of about 0.16 ,, g/g. The concentration of Kepone oysters picked up
from the dissolved state and from the sediment-bound state, as calculated
above, is representative of the actual concentrations found in oysters
collected from the James River.
^
Thus, our calculations show that between 30 and 46 7* of the Kepone
concentrated by oysters may originate by uptake from the dissolved state. We
recommend that detailed studies be conducted to establish the relative
importance of sediment-bound and dissolved Kepone in uptake by oysters and
other filter feeding organisms.
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Jtl
No laboratory uptake studies were conducted with the wedge clam Rang ia
cuneata during the contract period October 1977 to September 1978. The data
presented in our previous report for the period December 1977 to September
1978 included four uptake studies in the laboratory.
Those earlier studies suggested that the Kepone uptake trends in Rnngia
were similar to those in oysters. 'As with oysters, there were indications
that the concentration of Kepone in Rangia reaches a steady state in about
one week given a relatively constant concentration of Kepone in the sediment
suspension. They also indicated that, as was also the case with oysters, a
steady state in the concentration of Kepone in Kangia clams is attained in
about one week. A good correlation was obtained between Kepone in Rang ia and
the mean hourly concentration of Kepone in the sediment suspensions during
the week preceding sampling of the animals.
The information obtained in the laboratory was corroborated by the data
collected during the two types of field studies with Rangija conducted in
1978. Clarns held in plastic trays receiving water pumped from Skiffes Creek
at Fort Eustis, as well as those held in a wire bag on the bottom at Deep
Water Shoal, showed that the uptake curve levels off beginning with the first
week. The Skiffes Creek study included data that showed that clams exposed
to Kepone in suspended sediments for one week contained almost as much Kepone
as darns in their second or third week of exposure when the exposure period
of the groups of clams coincided in the same experiment.
Another similarity in the uptake behavior of oysters and Rangia was the
inverse relationship between the concentration factors for the animals and
the Kepone concentration in the suspended sediments. .The differences in
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slope and Y-intercept between the regression lines for oysters and Rangia
would probably be rendered not significant by the associated variation in the
two sets of data. An inference on uptake of Kepone from solution similar to
the one made for oysters could also be made for Rangia based on the
similarity of the data collected.
As with oysters, we found no evidence of a correlation between Kepone in
Rangia and Kepone on the sediment particles or between the concentration
factor based on the Kepone adsorbed on the sediment particles and the Kepone
on the particles.
The results obtained fron analysis of the material (biodeposits and
gravity-settling sediments) that accumulated in the plastic trays during the
experiments at Skiffes Creek and Deep Creek point^ out another similarity in
the biodepositional activity of oysters and Rangia. In both groups of
experiments, the Kepone concentration in the control trays without animals
was usually as high as in the trays holding oysters or clams. This lack of a
difference has been discussed already in reference to oysters.
Discussion of the data collected for the wedge clam Rangia cuneata may
be summarized by stating that the activity of Rangia in concentration of
Kepone and its subsequent biodeposition parallels that of oysters. These two
bivalves cover together a large portion of the James River and are found
there in large numbers. Therefore, the activity of these animals becomes a
factor of major significance in retention or dispersion of Kepone in the
James River.
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We only conducted one experiment each with the clams Macoma balthica and
Mulinia lateralis. Those experiments showed that these animals are also able
to concentrate Kepone with great efficiency. The data collected for Macoma
were presented and discussed in the previous report. No further data were
collected during the period covered by the present report. Mulinia clams
appeared to reach a body tissue equilibrium with Kepone in the sediment
suspensions in one week and, as did oysters and Kangia, they depurated
themselves of Kepone very quickly. They lost almost all their Kepone in less
than one week. These few data po i n t £1,*** t o the ease with which different t c^t%jV
groups of bivalve molluscs pick up Kepone and the apparent ease with which
they lose i t .
Experiments with the Asiatic clam Corbicula mani lensi s%were hampered by
*
the apparent inability of this clam to function "normally" under our
experimental conditions in the laboratory. Further efforts to obtain
acceptable data were deemed unjustified in view of the time and funding
restrictions. However, further investigations in uptake and depuration
behavior of this organism are recommended since Corbicula is a significant
component of the freshwater fauna of the James River above and below
Hop ewe 11 .
Several attempts were made to study uptake of Kepone by the bloodworm
Glycera dibranchiata but were aborted when we ran into difficulties with
extraction of the pesticide from the worm tissues. Modified procedures used
consumed an extremely long time for a very few samples and recovery was only
20-30% at a concentration of Kepone of less than 0.2y[-|g/g.
/
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It is concluded that filter-feeding molluscs concentrate Kepone quickly
from the surrounding suspended sediments and water and deposit it in a
concentrated form on the bottom during biodeposition. Biodeposits initially
deposited on the surface (together with any contaminants such as Kepone) may
be mixed to depths ranging down to 12 cm in several weeks by benthic
invertebrates (Haven and Morales-AVaroo, 1966b; Kraeuter, Haven and
Morales-Alamo, MS in preparation). Such buried substances are then no longer
subject to transport or resuspension, except perhaps in case of a major
storm.
_ j
nay C
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