PB81-218331
Behavioral Assays for Effects of
Drilling Muds on Marine Animals
University of West Florida, Pensacola
Prepared for
Environmental Research Lab
Gulf Breeze, FL
Jun 81
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
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EPA 600/4-81-050
June 1981
PB81-218331
BEHAVIORAL ASSAYS FOR EFFECTS OF DRILLING MUDS ON MARINE ANIMALS
by
Paul V. Hamilton
Department of Biology
University of West Florida
Pensacola, Florida 32504
Grant R806121-01
Project Officer
Norman L. Richards
Environmental Research Laboratory
U.S. Environmental Protection Agency
Gulf Breeze, Florida 32561
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
GULF BREEZE, FLORIDA 32561
REPRODUCED BY
NATIONAL TECHNICAL
INFORMATION SERVICE
US. DEPAR1MHI OF COMMERCE
SPRMGFIElO, VA 22161
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rm en IRQ ' TECHNICAL REPORT DATA
tKLjbD . 1DO (Please read Instructions on the revene before completing)
1.REPOHTNO.
EPA-600/4-81-050
2.
PROJECT REPORT
3. RECIPIENT'S ACCESSION NO.
PBM 218331
TITLE AND SUBTITLE
BEHAVIORAL ASSAYS FOR EFFECTS OF DRILLING MUDS ON
MARINE ANIMALS
5. REPORT DATE
June 1981
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
PAUL V. HAMILTON
8. PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME AND ADDRESS
. DEPT. OF BIOLOGY
UNIVERSITY OF WEST FLORIDA
PENSACOLA, FLORIDA 32504
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
R806121
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Environmental Research Laboratory
Office of Research and Development
Gulf Breeze, Florida 32561
. TYPE OF REPORT AND PERIOD COVERED
FINAL(7/l/78-3/31/8Q)
14. SPONSORING AGENCY CODE
EPA/600/4
IS. SUPPLEMENTARY NOTES
ABSTRACT
This report describes an electronic method for monitoring the shell movements
and water pumping of bivalved molluscs, data on the influence of whole drilling mud
and other particulate materials on the shell movements of scallops (obtained using
the electronic monitor), and a Submersible Monitoring Unit (SMU) for recording
these behaviors from bivalves held in field conditions. The electronic monitor
employs integrated circuit chips and receives input from inductance transducer
(shell movements) and thermistor (water pumping) sensors. Whole drilling mud caused
significantly more major Rapid Valve Closures (RVC's) at concentrations of 400 ppm
and higher,.and a significantly greater cumulative magnitude of all RVC's at 200 ppm
and higher. Barite, lignosulphonate and calcium carbonate revealed no clear dose-
response relationship for these two shell movement parameters, but all three of
these particulates produced similar patterns of effect. The SMU is.completely
self-contained; a battery powered circuit and tape recorder permit recording shell
movement data on a magnetic tape, which is later retrieved for analysis.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. , DESCRIPTORS
Organic compounds
Mollusca
18. DISTRIBUTION STATEMENT '
Release to public
b.lDENTIFIERS/OPEN ENDED TERMS
shell movement
water pumping
bivalve molluscs
19. SECURITY CLASS (This Report)
unclassified
20. SECURITY CLASS (This page)
unclassified
c. COSATI Field/Group
06/F
21.
22. PRICE
EPA Form 2220-1 (Rav. 4-77) PREVIOUS EDITION is OBSOLETE
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DISCLAIMER
This report has been reviewed by the Environmental Research Laboratory,
U.S. Environmental Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the views and policies
of the U.S. Environmental Protection Agency, nor does mention of trade names
or commerical products constitute endorsement or recommendation for use.
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FOREWORD
The protection of our estuarine and coastal areas from damage caused
by toxic organic pollutants requires that regulations restricting the intro-
duction of these compounds into the environment be formulated on a sound
scientific basis. Accurate information describing dose-response relation-
ships for organisms and ecosystems under varying conditions is required.
The Environmental Research Laboratory, Gulf Breeze, contributes to this
information through research programs aimed at determining:
. the effects of toxic organic pollutants on individual species
and communities of organisms;
. the effects of toxic organics on ecosystems processes and
components ;
. the significance of chemical carcinogens in the estuarine
and marine environments.
Over the past decade, oil and gas drilling operations have resulted
in millions of cubic feet of drilling muds and other byproducts being
released into the marine environment. This report describes a project
directed toward improving methods of determining the sublethal effects
of drilling muds and components on scallops. The results of this study
will be used to aid in the assessment of the potential impact of drilling
mud. discharge on marine organisms and ecosystems.
nos
Di rector
Environmental Research Laboratory
Gulf Breeze, Florida
TIT
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ABSTRACT
This report describes an electronic method for monitoring the shell
movements and water pumping of bivalved molluscs, data on the influence of
whole drilling mud and other particulate materials on the shell movements of
scallops (obtained using the electronic monitor), and a Submersible Monitor-
ing Unit (SMU) for recording these behaviors from bivalves held in field
conditions. The electronic monitor employs integrated circuit chips and
received input from inductance transducer (shell movements) and thermistor
(water pumping) sensors. Whole drill!ing mud caused significantly more major
Rapid Valve Censures (RVC's) at concentrations of 400 ppm and higher, and a
significantly greater cumulative magnitude of all RVC's at 200 ppm and
higher. Barite, lignosulphonate and calcium carbonate revealed no clear
dose-relationship for these two shell movement parameters, but all three
of these particulates produced similar patterns of effect. The SMU is
completely self-contained; a battery powered circuit and tape recorder
permit recording shell movement data on a magnetic tape, which is later
retrieved for analysis.
iv
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r
CONTENTS
Foreword i i i
Abstract iv
Figures vi
Overview vi i i
Acknowledgements ix
1. Section 2 1
An Electronic Method of Monitoring Valve Gaping Water
Pumping in Bivalved Molluscs , 1
Apparatus 4
Monitoring Frame 4
She! 1 Movement Ci rcui t 7
Water Pumping Circuit, 9
Voltage-to-Frequency Converter 15
Frequence-to-Vol tage Converter 15
2. Section 3 , 17
Effects of Drilling Muds and Selected Mud Components on
the Shel 1 Movements of Seal 1 ops.. 17
Materials and Methods .-,,...... 19
Results 23
Discussion 33
3. Section 4 38
A Submersible Monitoring Unit for the Behavior of Scallops
and Other Bivalves. 38
Basic Framework and Components ... 39
Monitoring Frame .-.;..... 39
Circuit Housing 43
Sampl e Data 45
Possible Modifications of the SMU 45
Section 5. References 49
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FIGURES
Number Page
2.1 Frame used to hold a test scallop in position while
moni tori ng i ts valve movements 5
2.2 Schematic diagram of the shell movement circuit 8
2.3 Rapid valve closures exhibited by a scallop, Argopecten
irradians, during normal filter feeding behavior and
series of rapid valve closures associated with swimming
attempts 10
2.4 Paired traces of the water pumped by a scallop and the
simultaneous shell movements of the same scallop 12
2.5 A simple single-thermistor sensor circuit for monitoring
water pumping by a scallop or other filter feeding
organi sm 13
2.6 Paired trace of water pumped by a scallop and the
simultaneous shell movements of the same scallop 14
2.7 Schematic diagram of the frequency-to-voltage converter 16
3.1 Relationship between the concentrations of five materials and
the average change they caused in the distance the values
of scallops are gaped '24
3.2 Relationship between the concentrations of five materials and
the average change they caused in the magnitude of Rapid
Val ve Cl osures 25
3.3 Relationship between the concentrations of five materials and
the average change they caused in the number of all RVC's.. 27
3.4 Frequency distributions for the magnitude of all RVC''s exhib-
ited by each of two scallops during 54-minute pre-dose
moni tori ng peri ods 28
3.5 Relationship between the concentration of whole mud and the
paired sea water controls, and the average change they
caused in the number of major RVC's 30
VI
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Number Page
3.6 Relationship between the concentrations of barite, ligno-
sulphonate and calcium carbonate, and the average
change they caused in the number of major RVC's 31
3.7 Relationship between the concentration of whole mud and the
paired sea water controls, and the average change they
caused in the cumulative magnitude of all RVC's 32
3.8 Relationship between the concentration of barite, ligno-
sulphonate and calcium carbonate, and the average
change they caused in the cumulative magnitude of all
RVC' s 34
4.1 Photographs of the entire SMU 40
4.2 Block diagram showing the components contained in the circuit
housing of the SMU : 44
4.3 Two segments of a 60 minute record of valve movements made by
the scallop Argopecten irradians 46
vn
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SECTION 1
OVERVIEW
The research funded by this grant had the following three objectives:
1. To develop an apparatus for remotely recording water pumping
and valve movements by scallops in a laboratory environment.
2. To obtain data on the effects of whole drilling muds and selected
mud components on filter feeding, using the appartaus developed
in the first objective.
3. To adapt the apparatus developed in the first objective to
permit recording these data from scallops held in field
conditions, and to perform field tests of this Submersible
Monitoring Unit (SMU).
These objectives are covered by the following three sections of this
final report.
vvn
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ACKNOWLEDGEMENTS
R.K. Pegg and M. Winter, my primary research assistants on this
> .
project, made many significant contributions and willingly worked many
hours beyond the call of duty. I also thank C. Ashton, G.S. Gripe, R.
Cripe, R.L. Koelling, D. Morton, N. Rubenstein, J.M. Sprouse, D. Thompson,
A.F. Tomlinson and E. Winter for technical suggestions and assistance, and
N.L. Richards for loan of equipment. This work was supported by an
Environmental Protection Agency Grant, R806121-01.
'IX
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Section 2: An Electronic Method of Monitoring Valve Gaping and Water
Pumping in Bivalved Molluscs
Filtering organic material from water is a common feeding strategy
among marine and aquatic animals, and is the dominant strategy among primary
consumers (J^rgenson, 1966). Because bivalved molluscs are one of the
largest groups of filter feeding animals, numerous studies have been con-
ducted on the mechanism of filter feeding and, particularly, on how various
factors (e.g., salinity, size and concentration of particles, pollutants)
influence filter feeding.
There exist several measurable components of filter feeding behavior
in bivalves. First, the valves must be gaped for water to flow through the
mantle cavity; consequently, the incurrent and excurrent aperture sizes in-
fluence the rate of water flow. Hence, the width the valves are gaped
comprises one measure of filter feeding activity. Second, the water current
passing through the mantle cavity is produced by the beating of cilia on the
gill. Hence, the rate of water flow comprises another measure of filter
feeding activity. Finally, eulamellibranch bivalves sort particulate matter
collected on the incurrent gill .surfaces, and form aggregates of- uningestible
particles called 'pseudofeces.' When sufficient pseudofeces are..collected,
the valves are rapidly closed, driving water out of the mantle cavity in
all directions, including out the normally inhalent opening. Pseudofeces
are carried out of the mantle cavity by this flow of water. Subsequently,
the valves are opened and the cilia recommence beating (Yonge, 1947; Owen,
1966). Because the rate of pseudofeces ejection depends on the concentration
of uningestible particulate matter in the water, the frequency of these
1
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single rapid valve closures comprises a third measure of filter feeding
activity in bivalves.
The number of techniques used for monitoring filter feeding in bivalves
almost equals the number of studies completed. Water puinping by bivalved
molluscs has been measured directly by inserting a rubber tube into the
gill cavity or by attaching a rubber sleeve to the shell, and then by
permitting the exhalent water to fill a calibrated measuring chamber
(Galtsoff, 1926: Nelson, 1936; Loosanoff and Engle, 1947; Loosanoff and
Tommers, 1948; Odlaug, 1948; Tammes and Oral, 1955; Loosanoff, 1961;
Drinnan, 1964) or to drip onto a pair of electrodes (Davids, 1964). Other
studies have measured water flow by observing movements of dye (Cough!an
and Ansell, 1964) or various particles. For example, Hersh (1960) used
cinematography to study the movement of particles, including tobacco mosaic
virus. Still other researchers have studied water pumping indirectly by
measuring the removal of suspended material by organisms. Haven and
Morales-Alamo (1970) used a Coulter counter to compare the concentration
of particles in water entering a chamber containing oysters to that leaving
the chamber, while Tammes and Oral (1955) used a colorimeter for the same
purpose. Chipman and Hopkins (1954) and Dorn (1976) measured clearing and
uptake of radioactively labelled plankton and diatoms. Some of these
latter studies also obtained information on retention of different sizes
of particles.
Over the past 15 years, several researchers have used thermistor flow-
meters in the field to measure the water flow produced by such filter
feeding organisms as sponges (Reiswig, 1971; LaBarbera and Vogel, 1976),
brachiopods (McCammon, 1965) and tunicates (Fiala-Medioni, 1978). Different
2
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speeds of water, flow take up different amounts of heat from a thermistor;
hence, because the amount of electrical current passing through a
thermistor changes with the thermistor's temperature, changes in the speed
of water flow produce electrical changes. I have found no studies using
thermistors to monitor bivalve water pumping.
Valve movements in bivalved molluscs have primarily been measured
using simple mechanical linkages to pens on kymographs (Loosanoff and
Engle, 1947; Loosanoff and Tommers, 1948; Butler et al., 1960; Lossanoff,
1961). More recently, Davenport (1979), Manley and Davenport (1979),
and Davenport and Manley (1978) monitored shell movements using a strain
gauge. The electrical current flowing through this type of component
changes as its shape is physically changed. Scallop shell movements
have also been monitored using strain gauges by researchers studying
swimming as an escape response (Thomas and Gruffydd, 1971; Stephens and
Boyle, 1978).
Many of the techniques described above are somewhat cumbersome and. it
1s difficult to envision using them effectively in field conditions. Further-
more, in most cases the data are expressed in a visual format, thus requiring
tedious conversion to achieve compatibility with a magnetic tape recorder
for storage or a computer for analysis.
Herein I describe an electronic method for monitoring filter feeding
in bivalves. Shell movements are continuously monitored by arv inductance
tranducer, thus providing data on gape width, frequency of pseudofeces
ejection and, in swimming species such as scallops, the frequency of
swimming attempts. Water pumped from the mantle cavity is monitored by a
thermistor positioned outside the exhalent aperture. Changes in shell gape
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and water pumping rate result in changes in output voltages from their
respective monitoring circuits. These voltages may be portrayed directly
on a chart recorder or they may be converted to frequency-modulated audio
signals and stored on magnetic tape for subsequent analysis.
This system of monitoring filter feeding in bivalves has been used
in laboratory studies on the effects of pollutants on scallops (section 3),
and has been modified, to permit long-term recordings in the field (section
4).
APPARATUS
Monitoring Frame
The scallop (or other bivalve) is attached to a monitoring frame
which holds the inductance tranducer, its mechanical linkage, and the
thermistor probe (see Figure 2.1). The framework of the holding apparatus
was constructed from 1.3 and 1.9 cm (I.D.) PVC pipe and fittings; the
shapes of some fittings were modified for specific purposes. The rubber
'\
plunger portion of a PLASTIPAK 50cc syringe was used as a form-fitting seat
for the scallop. After cleaning and drying the lower valve of the scallop
(the right valve), a small wire loop was attached to this valve using an
epoxy putty. A hook attached to one end of a threaded shaft passed through
a hole in the seat and seat support, and a wing nut on the opposite end of
the shaft permitted the scallop to be drawn down against the rubber seat.
A miniature nylon clevis was attached to the upper valve of the
scallop (the left valve) using form-fitting epoxy putty and PERMABOND.
This clevis permitted mechanical linkage of the upper valve to a loop of
3.6 kg-test nylon line. This line was routed around two 2.54 cm diameter
nylon pulleys and its tension was set with a miniature brass turnbuckle.
4
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TB
Figure 2.1. Frame used to hold a test scallop in position while monitoring
Its,.valve movements. (S=scallop's right valve; RS=rubber seat; WM=wing nut
for tightening hold-down hook; NC=nylon clevis attachment; TB=adjustab1e
boom with thermistor at its tip; RC=reference coil; JB=junction box; SC=
sensor coil; SS=steel slug; NL=nylon line; TB=turnbuckle; P=pulley; CC=main
connecting cable) 5
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On the same side of the loop as the scallop, a 2.5 mm diameter, 20 mm long
steel slug (section of galvanized 8 d nail), sheathed in plastic (heat-
shrink tubing),.was attached to the line using miniature brass eyebolts
glued (PERMABOND) to the plastic sheath. As the scallop moved its upper
valve, the steel slug travelled vertically through a plastic tube (9mm inside
diameter) around which the sensor coil was wound. The coil was 20 mm long
and had an estimated inductance of 437 microhenries with an air core.
Movement of this slug changed the inductance of the coil. The brass eye-
bolts had no appreciable effect on the coil's inductance. A second coil,
identical to the first except for lacking the steel slug, was attached
elsewhere on the monitoring frame and served as a reference coil.
Friction of the nylon pulleys was negligible. The clevis and steel
slug (3 gm total) were located on one side of the loop of nylon line while
the turnbuckle (1 gm) was located on the opposite side. Thus the scallop's
hinge ligament had to lift the difference in these weights, 2 gm, in the
process of opening the valves. The adductor must have been aided in its
action by the weight of these objects. This is the identical situation
encountered by scallops whose upper valves havevarious organisms attached
to them in nature (e.g., solitary tunicates, Crepidula, chitons, serpulid
worm tubes, hydrozoan colonies). I have frequently encountered scallops
with more than 5 gm (total dry weight) of these organisms on the
upper valve. Consequently, I conclude that this procedure for monitoring
valve gaping exerts counterforces upon the movement of a scallop's valve
that are less than those exerted by natural shell encrusting organisms.
The thermistor was embedded in the tip of an adjustable plastic
boom. This boom was positioned so the sensor thermistor was located just
6
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outside the large posterior exhalent aperture of the scallop. While some
water flows out anterior to the hinge, in Argopecten irradians the greatest
exhalent flow is posterior during normal filter feeding behavior; this is
generally the case among other non-gastropod molluscs. Dakin (1909)
reported similar observations for Pecten maximus. Water may be driven
out anterior from the hinge during swimming (Outsell, 1930).
Sensors were connected by waterproof cables to a section of the mon-
itoring frame designated as the junction box. This area was waterproofed
with wax after all connections were made. One large waterproof cable
connected this portion of the frame to the associated circuitry and
recording equipment located elsewhere.
Shell Movement Circuit
A sine-wave oscillator (1240 Hz @5.5 vac output) has its output
connected to both the reference and sensor coils. Two full-wave rectifiers
sample the voltage drops across the coils; when the coil inductances are
equal, equal voltage drops occur across them. Since the rectifiers rectify
the 1240 Hz voltages they sample in opposite polarities, their outputs
cancel exactly and 0 vdc is fed to the recording device. As the steel slug
moves into the field of the sensor coil, its inductance increases and the
voltage drop across it increases. Since the reference coil's inductance
remains unchanged, the output of the positive full-wave rectifier becomes
greater than that of the negative full-wave rectifier; after their.effects
are combined at the output potentiometer, a positive voltage is fed to the
recording device.
A schematic diagram of this circuit is shown in Figure 2.2. Portions
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B
#344
oo
REFERENCE COIL
f
OUTPUT
SENSOR COIL WATERPROOF
CABLE
POSITIVE FULL-WAVE RECTIFIER
(AS ABOVE BUT WITH DIODES REVERSED)
Figure 2.2. Schematic diagram of the shell movement circuit. It is comprised of an oscillator and
sensor coils (A) and two full-wave rectifiers (B). All resistors have a .5-W rating and 5% tolerance,
except for the 20K and 20K fixed resistors which have a 1% tolerance. The 741 integrated circuits are
powered by *15 vdc. The output may lead to a chart recorder or a voltage-to-frequency converter for
recording on a magnetic tape.
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of this circuit were modified from Jung (1974). Resistor Rl comprises the
primary load for the oscillator output as the coils themselves comprise
only a small load; the large capacitors (272 mfd)5p>ovide dp' isolation
from ground but little capacitive reactance for the oscillating signal.
Potentiometer R2 permits zeroing the circuit output when the steel slug is
out of the sensor coil. Only the schematic of- the positive full-wave
rectifier is shown in detail; the negative rectifier is identical except
the polarities of its two diodes are reversed. An offset null adjust (R3)
is used for the second amplifier of each rectifier to insure that zero out-
put is produced when there is no input signal.
A log-log plot of the relationship between output voltage and slug
insertion is approximately linear, and can be described by the following
equation: .—
log x -log y + 2.31
2.07
where, x= slug insertion (mm)
y= output voltage (mv)
Sample traces of valve moments associated with normal filter feeding
behavior are shown in Figures 2.4 and 2.6. Figure 2.3 shows a trace of
the repeated rapid valve movements associated with normal filter feeding.
Argopecten i rradi ans.
Water Pumping Circuit
Initially, I attempted to develop a thermistor sensor circuit that
would operate through a range of ambient current velocities while retaining
sensitivity to the small currents produced by a pumping scallop. I modified
' g ' . ' • .
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. 60 sec.
Figure 2.3. Rapid valve closures exhibited by a scallop, Argopecten
irradians, during normal filter feeding behavior (top) and series of rapid
valve closures associated with swimming attempts (bottom). Most swimming
attempts lasted less than 5 seconds. The single rapid valve closures
(top), which are frequently associated with a visible pseudofeces or feces
ejection, are typically followed by a step-wise or "staircase" reopening
of the shell. This situation was also noted by Thomas and Gruffydd (1971)
for Pecten maximus.
10
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the thermistor current meter described by LaBarbera and Vogel (1976:Figure
•
1A,B) so that both thermistors were exposed to water currents; one was
positioned above the scallop and was exposed to the ambient water current
only, while the other was positioned outside the posterior exhalant aperature
of the scallop and was exposed to both the ambient water current and the
exhalant water flow of the scallop. The circuit produced a de voltage
proportional to the difference in water flow over the two thermistors. I
used YSI-44002A precision thermistors and modified the other components
of LaBarbera and Vogel's bridge circuit appropriately.
This circuit worked adequately in calm water, as shown in Figure
2.4. However, the water pumping trace became somewhat irregular (noisy)
when aeration was begun in the tank, and temporal changes in water pumping
by the scallop became completely disguised by noise when even the slowest
water current was induced by the paddles. These irregularities in the trace
did not result from insufficient electrical current being fed through the
thermistors. I suspect the trace irregularities were caused by irregular
water flow patterns in the vicinity of the thermistor whose magnitudes ..,..-.,.
were greater than the water current produced by the pumping scallop.
Since this problem would affect any thermistor regardless of the
sophistication of its associated monitoring circuit, I developed a much
simpler circuit for monitoring water pumping of scallops of other bivalves
in calm water. The circuit is illustrated in Figure 2.5 and paired traces
are shown in Figure 2.6. Only a single YSI-44002A thermistor is used.
Resistor Rl sets the electrical current flow through the bridge, thus
adjusting the sensitivity of the thermistor for different water temperature
conditions. Resistor R2 balances the bridge for zero output when the scallop
11
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/i
. 60 sec .
Figure 2.4. Paired traces of the water pumped by a scallop (bottom) and
the simultaneous shell movements of the same scallop (top), obtained
using a modified version of LaBarbera and Vogel's (1976) thermistor
current meter. Traces were recorded in calm water (no aeration, paddles
stopped).
12
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WATERPROOF
CABLE
Figure 2.5. A simple single-thermistor sensor circuit for monitoring water
pumping by a scallop or other filter feeding organism. Paired traces
obtained using this circuit are shown in Figure 2.6.
13
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. 60 sec.
Figure 2.6. Paired traces of water pumped by a scallop (bottom) and the
simultaneous shell movements of the same scallop (top), obtained using
the simple thermistor circuit shown in Figure 2.5. Interestingly, these
traces showed a rapid increase in water pumping after a rapid valve
closure but a much slower reopening of the valves. Because the valves
rarely close completely, this effect may be related to the increased
velocity of water flowing through a smaller aperture.
14
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Is not pumping. Neither of these circuits is temperature compensated and
neither measure absolute current flow. These features are not considered
problems because the circuits would necessarily be used in a controlled
laboratory environment and researchers are usually most interested in
changes in water pumping, or in measuring pumping as percent of normal
response.
Voltage-to-Freguency Converter
For storage of data from the shell movement circuit on magnetic tape,
we employed the basic circuit described by LaBarbera and Vogel (1976:Figure
1C). However, we replaced their 15K resistor linking the input to pin 7
of the 555 timer with a 23K resistor. Also, we deliberately adjusted the
output potentiometer of the shell movement circuit (R2) for about 2.3 vdc
output when the slug was out.of the sensor coil so the timer would always
have some voltage biasing this pin. (We adjusted R2 for 0 vdc when the
output was fed directly to a chart recorder.) With this bias, the timer
pulses at about 1 KHz. As the slug enters the coil, the pin 7 input
increases as does the timer pulse frequency. Timer output is connected ..:
directly to the input of a tape recorder.
Frequency-to-Voltage Converter
To retrieve the data from the magnetic tape, we modified the circuit
described by LaBarbera and Vogel (1976:Figure ID). Our circuit is shown
in Figure 2.7. In order to reduce extraneous noise, magnetic tape casettes
were played back with the best quality tape recorder available, (We used a
WOLLANSAK 2551.)
15
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INPUT
•i f- i
- j ( j
°\ r
1 I 1
6A 1K
i C *. \ . Y
[1N914 ]
<
S II 1
r
DoOpr
1
>
5 100K
5100K
'
i
5!
I
55
(
)
01
in — '
= .05
hJ
Kit ^
<,
1Meg,
<:
i
>
>
•
>
i^
1Meg^
1
1Me
r\
r*'-^
r^
L "
_L
a o
<"
10K
<-15v
OUTPUT
O
1N914
Figure 2.7. Schematic diagram of the frequency-to-voltage converter I modified from LaBarbera and
Vogel (1976). The 741 integrated circuit is powered by ±15 vdc.
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Section_3: Effects of Drilling Muds and Selected Mud Components on the
Shell Movements of Scallops.
During the process of drilling for oil in the marine environment,
quanities of drilling muds and drilled-up solids (cuttings) are discharged
into the surrounding water. Drilling muds are chemically complex and con-
tain both water soluble and water insoluble components. A visible plume
containing drilling mud and cuttings is produced by the prevailing water
currents. Thus this material is distributed in the water column and on the
bottom in the area around the drilling rig (McGuire, 1975; Monaghan et al.,'
1976;^ Richards, 1977). ..'/'.!
Few critical studies have been directed toward evaluating the influence
of whole mud or its components on the environment. Effects of whole drilling
mud or its important components have been documented on the composition of
benthic communities (Tagatz et al., 1977, 1978a, 1979b; Tagatz and Tobfa,
1978; Cantelmo and Rao, 1978a,b; Cantelmo et al., 1979). Thompson and
Bright (1977) studied the sediment clearing response of hermatypic coral
polyps. Polyps were unable to remove whole drilling muds but could remove
equal doses of barite, aquagel and calcium carbonate. Studies on other
species and other behaviors are lacking.
The commercial scallop, Argopecten irradians,was chosen for study of
the effects of drilling muds for several reasons. First, most of what com-
prises drilling mud consists of fine particulate matter which remains in
suspension for varying amounts of time. Hence, it would seem that filter
feeding organisms would be the first to come in direct contact with this
material. Second, scallops can swim and, according to some biologists,
they are supposedly capable of migration. Although the.migration question
17
-------
is far from answered (see Baird, 1966; Hartnoll, 1967), scallops do swim
in response to predators (e.g., Thomas and Gruffydd, 1971; Stephens and
Boyle, 1978). Since Ensis and other normally infaunal bivalves will sometimes
swim in response to degraded water quality, (Ansell, 1969), it was anticipated
that scallops, for which swimming is a much more common behavior, might
swim and be carried horizontally by ambient water currents when exposed to
poor water quality. Similar strategies are involved in the migrations of
eel elvers (Creutzberg, 1963), portunid crabs (Venema and Creutzberg, 1973)
and shrimp (Hughes, 1969), and may occur in other molluscs (Hamilton and
Ambrose, 1975; Schuhmacher, 1973). Third, scallops are found in areas of
the Gulf of Mexico where drilling occurs. The bay scallop, Argopecten
irradians, was once very common in Mobile Bay, Alabama, and the Pensacola
estuary, though it is less so now. (The mud sample tested in this study
came from a drilling rig at the,mouth of Mobile Bay.) The calico scallop,
Argopecten gibbus, is found further offshore in the Gulf of Mexico where
drilling operations occur more frequently. Finally, scallops are com-
mercially important. The fishery for bay scallops has markedly declined
over the past 10 years in Florida and the calico scallop fishery is currently
following a sharp downward trend (Florida Landings).
This study was designed to measure the effects of different doses of
whole drilling mud and of two major particulate components on the filter
feeding responses of the bay scallop, Argopecten irradians. These effects
were compared to those caused by equal doses of calcium carbonate and by
clean but unfiltered sea water (the control). Because the valve movements
of a bivalve have not been analyzed in detail before, it was not known
18
-------
which parameters would clearly reveal responses to participate matter and
which ones would not. Therefore, this study also comprises an analysis of
the relative reliability of several different valve movement parameters
as indicators of response to particulate material.
METHODS AND MATERIALS
Valve movements of scallops were monitored using the frame and electronic
circuitry described in. Section 2. Water pumping was not measured because
the necessary monitoring circuit had not yet been perfected at the time
these studies were begun. Two scallops mounted on individual monitoring
frames were maintained in each of two tanks while their behavior was re-.
-corded. Each tank contained 126 liters of unfiltered ambient sea water.
The outputs of the four valve gape monitoring circuits were recorded on two
OMNISCRIBE B-5000 dual-channel chart recorders (Houston Instrument Co.),
operating at 2.5 cm/min.
The circular test tanks were custom made following the basic design
of Creutzberg (1963) and Venema and Creutzberg (1973). The inside diameter
of the tanks was 61 cm and the inside diameter of the paddle-containing ,.
cylinder in the center was 30 cm. Each tank possessed a cone-shaped bottom;
a centered drain lead to an air-lift pipe which ran up the outside wall of
the tank and.into the outer portion. The cone shape and air-lift permitted
continuous recycling of the tank contents, thus keeping the particulate
materials in suspension. The paddles in the two tanks were driven with a
single^ Craftsman (.5 hp, 115 vac) variable-speed motor. A pulley reduction
array, a variable transformer and adjustable-pitch paddles permitted accurate
control of current speed. The current speed in the outer portion of the
tank (where the scallops were located) was 5.85 cm/sec during all tests
19
-------
described here. Two fluorescent bulbs were centered over each tank. The
tanks and all associated apparatus were housed in a small room from which
all people were excluded during test runs.
Adult scallops (shell height s45 mm) were collected periodically from
shallow grassflats in East Bay, Panama City, Florida. They were transported
to 10 cm deep outdoor runways at the Environmental Protection Agency Lab-
oratory on Santa Rosa Island. There they were exposed to natural photoperiod
and flow-through unfiltered seawater from Santa Rosa Sound. Temperature and
salinity were ambient. This same water, to which the animals were already
adapted, was also used in the two tanks during tests.
A 20-liter sample of whole drilling mud was obtained at 1130 hrs. on
August 7, 1979, from a Mobil Oil Co. exploratory drilling rig located near
the mouth of Mobile Bay, Alabama. The temperature of the mud entering the
mud room was about 77°C but the "mud engineer" estimated that at the hole's
bottom (then 5850 meters), the mud's temperature was over 175°C. The mud
sample was transported to the Environmental Protection Agency Laboratory in
Gulf Breeze, Florida, where it was stored temporarily at 13°C, and later
at 3°C. Samples were taken for testing after thoroughly mixing the mud
in the storage container. The mud had a smell resembling diesel fuel,
a material that is sometimes added to mud on drilling rigs.
Barite (barium sulphate; produce name IMCO-BAR) was obtained from the
Mobil rig on the same day. Barite (density, 4.25) is the major drilling mud
additive by weight. Another major component of drilling mud, lignosulfonate
[sic] was obtained from IMCO Services in Mobile (produce name IMCO RD-111),
the distributor that was supplying mud components to the same rig from which
the mud sample and barite were obtained. The distributor claimed this type
20
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of lignosulfonate contained sodium chromate, although their product
literature did not mention this. Powdered calcium carbonate (analytical
grade; density 2.75) was obtained from Mallinckrodt Chemical Works. When
aliquots of the mud sample were dried by heating, the average residue con-
centration was measured to be 440 gm/1. This figure was used to determine
the volume of whole drilling mud needed for standard concentrations in the
test tanks. Concentrations of barite, lignosulfonate and calcium carbonate
were computed on a weight basis. .
Tests of whole mud, barite, lignosulphonate, calcium carbonate and
undosed sea water were conducted from August 15, 1979, to February 20, 1980..
Over this period, the salinity of the water in the test tanks ranged from
18 to 26 ppt and the temperature ranged from 9 to 28°C. For a given con-
centration of test material (e.g., 400 ppm), 9 to 11 (usually 10) scallops
were tested with each of the four particulate materials, and with the sea-
water control, following a rotating sequence. Those few scallops which
exhibited fewer than three rapid valve closures during the pre-dose period
(see below) were discarded from the analysis. Once all scallops were tested
at one concentration, tests at the next concentration were begun.
Preliminary observations of scallops exposed, to undosed. seawater
revealed considerable variation in valve movement patterns among animals,
. with/much less variation for individual animals over time. For this reason,
I compared the responses of individuals before and after exposure to a test
material. After each scallop was attached to its monitoring frame, it was
suspended in a tank containing undosed seawater, with the tank paddles
running: twenty-five minutes after all four scallops were introduced to
their tanks (a period of acclimation), a 54-minute period of monitoring was
21
-------
begun; this was designated the pre-dose period. At the end of this period,
known amounts of whole mud, barite, lignosulfonate or calcium carbonate
were introduced to the appropriate tanks; nothing was added for the seawater
control tests but these scallops were equally disturbed by the investigator's
movements in the room. Preliminary observations indicated that 5 minutes
was sufficient time for undosed scallops to return to normal behavior after
departure of the investigator from the room. Therefore, 5 minutes after the
introduction of test materials a second 54-minute period of monitoring was
begun; this was designated the post-dose period.
The following .data were recorded for both the pre- and post-dose
periods of each scallop tested:
1. The instantaneous shell gape at 2 min. intervals. The average gape
distance for each period (n=27) was later computed. The change in
average gape distance between pre-and post-dose periods was taken
as the measure of the response of the animal.
2. The change in gape distance resulting from each RVC, the cumulative
total for the magnitude of all RVC's and the number of RVC's.
An RVC was defined as a closure resulting in a change in gape
width that was completed within 2 seconds. In practice, most
closures were completed in less than 1 sec and we were able to
detect valve closures as small as .3 mm. The magnitude of the
average RVC for each period was later computed, and 'major1 RVC's
(see below) were identified from all RVC's that occurred.
In summary, effects are presented in terms of change in shell gape,
change in average magnitude of all RVC's,change in the cumulative total of
all RVC's, change in the number of all RVC's, and change in the number of
22
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'major' RVC's. All pre- and post-dose comparisons were made using the
Paired t-test, (Zar, 1974) with .05 as the criterion level for significance.
RESULTS
Figure 3.1 shows the relationship between the average change in gape
distance of the valves for five concentrations of each of the four materials
tested, and for their corresponding seawater controls. None of the relation-
ships (including whole mud) exhibit clear trends and there are only a
few scattered points which are significant. For example, 400 ppm whole mud
caused a significant 3.23 mm decrease in gape distance and 50 ppm lignosul-
phonate caused a significant 2.47 mm increase. The change in valve gape.
observed in the seawater controls for the 100 ppm test group was the only
time seawater produced a significant effect for any valve movement parameter
in any of the test groups. These results indicate that changes in gape
distance of the valves, at least with the materials and concentrations tested,
are not a reliable measure of response.
Figure 3.2 shows the relationship between the average change in magni-
tude of all RVC's and concentrations of the materials tested. Again, none
of the relationships (including whole mud) exhibit clear trends and there
are only a few points which are significant. For example, 400 ppm whole
mud caused a 1.4 mm increase in closure magnitude while 200 ppm of lignosul-
phonate and barite caused .85 mm and .95 mm increases, respectively. These
results indicate that changes in the magnitude of all RVC's, at least with
the materials and concentrations tested, are not a reliable measure of
response.
23
-------
11
C/5
ca
is
-2-
-3-
CONTROL
400
CONCENTRATION (PPM)
i I
100 50
Figure 3.1. Relationship between the concentrations of five materials and
the average change they caused in the distance the valves of scallops are
gaped (open). The larger dots indicate points that are significantly
different from zero.
24
-------
1-
u_
o
0-
LU
•a:
-1-
CONTROL
BARITE'
MUD
I
600
I I
400 200
CONCENTRATION (PPM)
100 50
Figured,2. Relationship between the concentrations of five materials and
the average change they caused in the magnitude of Rapid Valve Closures
(RVC's). Larger dots indicate points significantly different from zero.
25
-------
Figure 3.3 shows the relationship between the average change in the
number of all RVC's and concentrations of the materials tested. All of the
particulate materials showed significant effects for at least two concen-
trations. Barite showed significant effects at all concentrations, even
at 50 ppm, where lignosulphonate also showed a significant effect. Although
the whole mud results suggested a crude relationship between dose and response,
there were no clear, trends for any of these particulates. The sea water
control produced uniformly low and insignificant effects. These results
indicate that changes in the number of all RVC's, at least with the materials
and concentrations tested, are only a marginally reliable measure of response.
It is apparent from observing traces of the valve movements of individual
scallops that a frequency distribution of the magnitude of RVC's is often
bimodal; over a period of time, scallops tend to exhibit either large
magnitude or low magnitude RVC's. Examples from two .scallops are shown in
Figure 3.4. Because large magnitude RVC's would seem more likely to be
associated with a pseudofeces ejection, it would be desirable to analyze
responses to particulates on the basis of changes in large magnitude RVC's,
or as I have termed them here, 'major' RVC's. The initial problem with this
approach is defining what constitutes a major RVC. Any such criterion needs
to be indexed for each specific animal; as illustrated in Figure 3.4, most
major RVC's for one scallop are in the 8 to 12 mm range*, while most major
RVC's for the other scallop are in the 5 to 9 mm range.
My solution to this problem is to define a major RVC for a scallop as
any RVC greater than or equal in magnitude to the average RVC exhibited
by the scallop during, the pre-dose period. This criterion is then applied
to both the pre- and post-dose RVC's to identify those RVC's which were
26
-------
20-
15-
Of
UJ
03
10-
UJ
OH
-5
LIGN.
BARITE
CALC.
CONTROL
1—
600
100 . • '200
CONCENTRATION (PPM)
"I T
100 50
Figure 3.3. Relationship between the concentrations of five materials and
the average change they caused in the number of all RVC's. Larger dots
indicate points significantly different from zero.
27
-------
20-
LU
Q_
N = 27
0
rz]
20-
LU
D_
N = 43
0
0
I
4 8 12
CLOSURE MAGNITUDE (MM)
i
16
Figure 3.4. Frequency distributions for the magnitude of all RVC's exhib-
ited by each of two scallops during 54-minute pre-dose monitoring periods,
28
-------
major for that animal. Figure 3.5 shows the relationship between concen-
tration and average change in number of major RVC's. for whole mud and the
paired sea water controls. A clear trend is evident in the dose^response
relationship for whole mud. Concentrations of 600 and 400 ppm caused
increases of 9.3 and 7.4 major RVC's, respectively; lower concentrations
of mud did not produce significant effects. The sea water control showed
no significant effects for any test group. These results indicate that
the change in number of major RVC's is a reliable indicator of response to
whole drilling mud.
V Figure 3.6 shows the relationship between concentration and average
change in number of major RVC's for barite, lignosulphonate and calcium
carbonate. All three of these particulates exhibited a peculiar dose-
response relationship, although only a few scattered points were significant.
An increase in major RVC's was seen at 200 ppm for a],1 three materials.
Calcium carbonate and barite produced equally low effects at lower con-
centrations (100 ppm, 50 ppm), but 50 ppm lignosulphonate produced a greater
increase in number of major RVC's than any of the materials at any of the
concentrations tested.
It is also apparent from observing traces of the valve movements of
individual scallops during post-dose periods that some individuals responded
by making few but large-magnitude RVC's while others responded by making
many but small-magnitude RVC's. Hence it would be desirable to analyze
responses on the basis of total magnitude of all closures during a period,
or as I have termed it here, 'cumulative magnitude' of all RVC's.
Figure 3.7 shows the relationship between concentration and the
average change in cumulative magnitude of all RVC's for whole mud and the
29 ":
-------
15-1
10-
° 5-
UJ
CO
CD
-5-
CONTROL
600
400 200
CONCENTRATION (PPM)
100 50
Figure 3.5. Relationship between the concentration of whole mud and the
paired sea water controls, and the average change they caused in the number
of major RVC's. Larger dots indicate points significantly different from
zero. Bars are standard errors.
30
-------
20-i
15-
oc
o
oa
10-
5-
-------
100-
80-
60-
~ 20
LU
i
UJ
-20J
CONTROL
100 50
CONCENTRATION (PPM)
Figure 3.7. Relationship between the concentration of whole mud and the
paired sea water controls, and the average change they caused in the
cumulative magnitude of all RVC's. Larger dots indicate points signif-
icantly different from zero. Bars are standard errors.
32
-------
paired sea water controls. A clear trend is evident in the dose-response
relationship for whole mud. Concentrations of 600,400 and 200 ppm caused
increases of 109,58 and 55 mm of total RVC's respectively; lower concen-
trations of mud did not produce significant effects. The sea water control
showed no significant effects for any test group. These results indicate
that the change in cumulative magnitude of all RVC's is a reliable indicator
of response to whole drilling mud.
Figure 3.8 shows the relationship between concentration and the
average change in cumulative magnitude of all RVC's for barite, lignosul-
phonate and calcium carbonate. As with the data in Figure 3.6, only a few
scattered points were significant but an increase in cumulative closures
was again seen at 200 ppm for all three materials. Calcium carbonate and
.barite produced equally low effects at lower concentrations, but 50 ppm
v . . .... .
lignosulphonate again produced a greater increase in total RVC's than any
of the materials at any of the concentrations tested.
DISCUSSION
Of the five valve movement parameters analyzed, two are not reliable
indicators of response (change in valve gape, change in RVC magnitude) and
a third parameter (change in number of all RVC's) is only a marginally
reliable indicator of responsiveness to whole drilling mud. The last two
parameters (change in number of major RVC's, change in cumulative RVC
magnitude) appear to be reliable indicators of responsiveness to whole
mud, presumably due to the fact that these, parameters are least influenced
by the natural variations exhibited by scallops. The major-RVC parameter
33
-------
120-
100-
80-
UJ
> 60-
I
LU
-------
permits defining what is a 'major1 or large closure for each scallop while
the cumulative-.RVC magnitude parameter ignores difference in response
patterns. Using these last two valve movement parameters, certain con-
clusions can be drawn about the effects of whole drilling mud and the
other particulate materials on this behavior.
The first conclusion is that whole drilling mud significantly increases
the number of major RVC's above 400 ppm and significantly increases the
cumulative magnitude of RVC's above 200 ppm. These results almost cer-
tainly reflect the increased number of pseudofeces ejections at these
doses. There was a clear dose-response relationship for both parameters
for whole mud (Figures 3.5, 3.7).
'the second conclusion is that a clear dose-response relationship does
not exist for the three other particulates tested (barite, lignosulphonate
and calcium carbonate), though as a group they all exhibited approximately
the same pattern of effect (Figures 3.6, 3.8). A greater effect was observed
for these three materials at 200 ppm than at either of the two higher concen-
trations, a situation not observed for whole mud, which was tested simul-
taneously. Presuming this phenomenon is real, there seems to be only one
reasonable explanation: for "pure" insoluble particulates, there is a con-
centration (e.g., 300 ppm) above which scallops tend to "give up trying"
to clear the gills via pseudofeces ejections, but some factor associated
with the complex composition of whole drilling mud over-rides this tendency.
The reality of this phenomenon could be tested via an acute toxicity study
because scallops which no longer keep their gills clean of particulates
are likely to experience higher mortality.
35
-------
Of the three particulates whose patterns of effect are illustrated
in Figures 3.6 and 3.8, barite and calcium carbonate appeared to have the
most similar patterns; lignosulphonate deviated the most from the basic
pattern at 50 ppm, the lowest concentration tested. A reasonable explanation
for this lies in the nature of the particles involved. Microscopic exami-
nation showed that the barite sample consisted of homogenous approximately-
spherical particles in the 3 to 5 urn size range. The powdered calcium
carbonate also consisted of homogenous approximately-spherical particles in
the 5 to 13 urn size range. Lignosulphonate, however, consisted of much
larger particles of two types; I estimate that about 10% of the particles
were spheres from 17 to 38 urn in diameter while 90% of the particles
had irregular oblong shapes with dimensions ranging from 60 to 110 urn in
width and 89 to 460 urn in length.
An additional facet of the similarity in patterns of effect for these
three particulates is a consideration of their relative densities. Barite
has a density of from 4.2 to 4.7 (IMCO Services product data) while calcium
carbonate's density is about 2.75. Because the concentrations of particulates
were prepared on a weight (ug/1) basis, this means that at any one concen-
tration (ppm), there were many more calcium carbonate particles than barite
particles. Based on particle count measurements using a hemocytometer, at
a concentration of, for example, 200 ppm, there were 26 x 106 calcium
carbonate particles/ml but only 8.36 x 10^ barite particles/ml. This
difference in density, coupled with the observed similarity in response
patterns for these two particulates when concentrations were prepared on a
weight basis, suggests that the mechanism of a scallop's response to par-
ticulate material involves discrimination of particle weight rather than
36
-------
particle number. The density of lignosulphonate was not obtained.
The third conclusion, which was alluded to above, is that whole
drilling mud has a different effect than its major component in "pure"
form (barite), and both other particulates tested (lignosulphonate, calcium
carbonate). This is not an unprecedented result and there are several
reasonable explanations for it. As mentioned earlier, Thompson and Bright
(1977) found that various corals were unable to clear whole mud settling on
their epidermis but could clear equal amounts of barite, calcium carbonate
and aquagel. Such a difference could be due to synergistic interactions of
the various constituents in whole mud or to the one or more constituents
of whole mud that were not tested separately. There was no evidence that
a biocide was being added to the mud at the time the test sample was
• ;i
obtained, but, as mentioned earlier, diesel fuel had apparently been added.
It would be interesting to test the effect of diesel fuel on the scallop
valve movement bioassay. Finally, the greater effect of.mud could be due
to any chemical changes that might occur when it is heated to temperatures
as high as those that exist at a drill hole's bottom.
37
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Section 4: A Submersible Monitoring Unit for the Behavior of Scallops
and Other Bivalves.
Accompanying the increased presence of pollutants in our environment
is the increased need for regulatory agencies to monitor these environments.
In the past, such monitoring has primarily consisted of water chemistry
measurements and descriptions of samples of the biota. More recently,
the value of behavioral studies in evaluating sub-lethal effects of
pollutants, in both the field and laboratory, has become increasingly
recognized.
Monitoring the behavior of an animal in the field is a useful
capability not only because it can reveal whether the animal is physiolog-
ically stressed, but also because it can reveal whether the animal is doing
anything that might change the probability of it being exposed to a pollu-
tant. This consideration is especially important in blvalved molluscs,
for example, because they are able to close the valves for considerable
periods of time. Where bivalves are used in field studies of bioaccumulation
or depuration of pollutants, it would be valuable to know the amounts of
time they were closed and open.
The prototype submersible monitoring unit (SMU) described' here was
originally developed for use with scallops, with the idea that a series of
such units might be deployed in a circular array around an active drilling
rig to monitor discharges of drilling muds and other materials. The SMU
could easily be used with other bivalves in other environments. For
38
-------
example, it could be used to insure that oysters were gaped (and hence
exposed to the surrounding water) during a period of exposure to effluent
from a sewage outfall.
The SMU is completely self-contained. Data are stored on magnetic tape
using a recorder housed in the unit and battery power is also included.
As currently designed, the SMU records only the valve movements of a single
scallop. However, at the end of this section, there are a series of sug-
gested modifications for the SMU which would extend its capabilities.
With little additional cost, six or more scallops could be monitored by a
single SMU. The water pumping sensor (Section 2) could also be added.
BASIC FRAMEWORK AND COMPONENTS
Aim tall vertical mast of 1.9 cm (I.D.) galvanized pipe is embedded
in a concrete-filled tire (50 cm O.D.). Two rubber coated handles are also
'% .!.• .
embedded in the concrete to facilitate handling-the unit which weighs about
60 kg in air. Adjustable sleeve fittings on the mast permit attachment
of the circuit housing and the monitoring frame. A galvanized steel shackle
is bolted to the top of the mast and a swivel connects this shackle to
sufficient 227-kg line to reach a surface buoy. A photograph of the
prototype SMU is shown in Figure 4.1A.
MONITORING FRAME
The monitoring frame is basically identical to that designed for and
used in laboratory studies (see Sections 2 and 3, respectively). However,
the junction box is filled with plastic resin which hardens to a waterproof
and pressure-resistant medium for greater isolation of the electrical
connections. Also, PVC pipe elbows and extensions at the top and bottom of
39
-------
Figure 4.1. Photographs of the entire SMU (A), the circuit box sitting
in its support basket (B), the monitoring frame holding a scallop (C) and
the magnetic tape recorder with the monitoring circuit board (D). In
photograph C, the loop of nylon line has been adjusted so that the steel
slug (right side of loop just beneath point where the clevis attached to
the scallop is connected to the line) has been raised above the sensor
coil below it. During normal operation, the slug would be inside the
plastic tube around which the coil was wound, and consequently out of view.
40
-------
-------
42
-------
the frame are used to mate it securely to the sleeves on the mast. Three
50 cm lengths of neoprene - coated cable (. 6 cm diameter) connect the mon-
itoring frame to the circuit housing. Photographs of the monitoring frame
are shown in Figure 4.1A.C.
CIRCUIT HOUSING
The circuit housing (Ikelite #5910) is made of 1.3 cm thick injection-
molded plexiglass and has a 1.9 cm thick cover with an 0-ring seal; its
inside dimensions are 12.7 x 22.9 x 20.3 cm. The manufacturer guarantees
it against leakage to beyond 107 m depth. Permanent stainless steel bulk-
head fittings (Ikelite #4007) were installed to accept the cables from the
monitoring frame. A basket of 1.3 cm (I.D.) PVC pipe holds the housing
securely to the sleeves on the mast. Photographs of the circuit housing
V..
are shown in Figure 4.1A.B.
A block diagram showing the major components contained in the circuit
housing is shown in Figure 4.2. All batteries shown, are 9 vdc nominal.
A 30-minute timer controls the power for the tape recorder so that the SMU
• -1
can be sealed and set down at a site, and the test animal has'time to
\
acclimate to conditions, before data recording starts. The regulators
maintain their voltages at prescribed levels over a range of battery
strengths. The monitoring circuit is identical to that shown in Figures
2.2 and 2.3 and the voltage-to-frequency converter circuit is identical to
that shown in Figure 2.4.
The tape cassette in the recorder I used (a modified version of GE
3-5001) lasts 60 minutes. After the data are recorded, and the SMU and
tape are retrieved, the audio output is fed to the frequency-to-voltage
converter described in Section 2. The resulting output voltage can then be
43
-------
9 VDC
BATTERIES
18 VDC
BATTERIES
18 VDC
BATTERIES
TIMER
SWITCH
+15 VDC
REGULATOR
+6 VDC
REGULATOR
§
a.
T
MONITORING
CIRCUIT
SENSOR
INPUTS
h-
a.
T
TAPE
RECORDER
INPUT
SIGNAL
OUTPUT
VOLTAGE TO
FREQUENCY
CONVERTER
TO MONITORING
FRAME
Figure 4.2. Block diagram showing the components contained in the circuit housing of the SMU.
The manufacturer reports the box can withstand pressures to 106 m of depth. The monitoring
frame is connected to the box by the waterproof cables and bulkhead connectors. The three
capacitors are 100 pF.
-------
fed to a conventional chart recorder (I used a Houston Instruments
OMNISCRIBE B-5000) to obtain a visual representation of the changes in
the test animal's valve movements over time. A photograph of the recorder
and printed circuit board is shown in Figure 4.ID.
SAMPLE DATA
I have tested the SMU in Santa Rosa Sound, Escambia County, Florida.
Salinity ranged from 20-25 ppt and water temperature from 11-14°C. Initial
tests revealed thermally-caused drift arid instability in the recorded signal.
This was subsequently remedied by a circuit modification. Thereafter I
observed a stable signal with only slight drift (down to 5°C, when the SMU
•S-c-
was tested in a laboratory coldroom).
Several sections of a 60 minute record obtained from a scallop monitored
at a depth of 2 meters in the field are shown in Figure 4.3. These data
were originally recorded on magnetic tape in the SMU and were later portrayed
on a chart recorded in the laboratory following the procedure described
above. In both segments, there is evidence of the valves re-opening in a
step-wise or "staircase" fashion, a situation also noted by Thomas and Gruffydd
(1971) for Pecten maximus. Closure of the valves was much more rapid. Also
in both segments, the scallop maintained a wider shell gape after the period
of relatively rapid shell movements than it maintained before this period.
POSSIBLE MODIFICATIONS OF THE SMU
l.":Often it would be desirable to operate an SMU for one or two weeks in
the field without having to service it. The following modifications of
the prototype would extend its operational capability:
A. The prototype SMU was powered by series and parallel combinations
of disposable 9 vdc alkaline batteries (.5 amp-hour). The SMU would operate
45
-------
E
E
in
30 sec
Figure 4.3. Two segments of a 60 minute record of valve movements made by
the scallop Argopecten irradians. The scallop was held at 2 m depth in
Santa Rosa Sound and its movements were recorded by the SMU. The data
were recorded on magnetic tape within the SMU, and the tape was later
'read' in the laboratory to obtain the record. An approximate scale for
gape width is given.
46
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for about 90 minutes on one set of batteries. Batteries that are rechargeable
and that have a higher amp-hour rating than the ones we used would improve
the SMU's capabilities. Sealed 'Gel-type1 rechargeable batteries are available
and,, although the initial investment would be significant (probably about
$200 for the batteries and $125 for the additional housing that would be
necessary/SMU), these would seem to be the best suited. Standard voltages
are 6 and 12 vdc, so if the circuits could be adjusted to operate on 12 vdc
rather than the present 15 vdc, they would be directly compatible.
B. Our magnetic tape recorder operated at the standard casette speed
of 1.875 ips (=4.76 cm/sec) and the longest lasting (=thinest) magnetic tape
permitted 60 minutes of continuous recording. Slower tape speeds could be
achieved by. altering the pulley size ratio or capstan diameter of the tape
recorder.
C. Continuous records of behavior may not be appropriate or necessary
for many applications. It might be desirable, for example, to record
behavior for only a 5-minute period at the beginning of every hour. A simple
microprocessor circuit could be added to the SMU which would turn on the
monitoring circuit and tape recorder for only the 5-minute sampling periods.
2. The prototype SMU records the valve movements of only a single bivalve.
A simple microprocessor circuit could be added to the SMU which switched a
single monitoring circuit through a sequence of several sensor codls, each
on a separate monitoring frame containing one bivalve. Thus,'the behavior
of a number of animals could be monitored, but not more than one at one
time. The microprocessor could be combined with the microprocessor described
above (1C) to achieve almost any sampling regime desired.
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3. Since considerable time and money would be invested in an SMU, a backup
method of locating and/or retrieving it (should the SMU-to-surface buoy
cable break) might be attractive. For this purpose, an emergency disconnect
could be installed near the base of the mast with control being via a sonic
pinger. Once the mast became detached from the concrete base, the natural
buoyancy of the circuit housing would bring the entire mast and attached
components to the surface. Alternately, a standard sonic pinger might be
attached to the SMU and its position could be located by a diver using a
hand-held receiver-hydrophone.
4. An additional investment of about $50 (for parts) would permit building
a circuit that would modify the analog signal coming from the monitoring
circuits to a digital signal which could then be analyzed directly by a
computer.
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Section 5
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