Bio 175H Research Project
Chuck Baxter, Advisor
H.M.S. Spring Qtr, 1993
A study of the vesicomyid clams in the Monterey Bay Canyon:
time-lapse video analysis of adult reactions to varying sulfide
levels, and examination of egg buoyancies and flotation rates
by Ben J. Meyer
Abstract:
This experiment was designed to study different aspects of development and
behavior of the vesicomyid clams in the cold seeps of the Monterey Canyon. It consisted
of two parts, a behavioral study done using time-lapse video and a study of the effects
simulated cold seep conditions had on the gametes of the clams. The first portion of the
project, the behavioral study, only allowed for developmental progress and gave
inconclusive results, so it was not discussed in this paper beyond pertinent information in
the introduction. The second portion of the project and the focus of this paper consisted
of testing the egg buoyancy of the eggs of different species. The majority of conclusive
data comes from C. pacifica, although some conclusions were available from the
vesicomyid species known as “Sharpbutt" also. A significant discovery in regards to the
condition of the eggs was that a mucus cloud released with the eggs during experimental
spawning and dissecting procedures greatly changed results when compared to those of
clean, free eggs. The difference in average rates was such that eggs in the presence of the
mucus were estimated to be able to climb 635m to the surface in approximately 2.5 days
while in 2.5 days many free-floating, clean eggs would have only climbed 5Om, with some
free eggs not ascending at all and some even sinking, a phenomenon never observed in the
presence of the translucent mucus. The implications this information holds for egg
survivorship and a specific environment of embryonic and larval development remains
speculative. This project solved many problems, exposed many new questions, provided
ground-breaking development (such as the creation of the first known egg buoyancy
chamber) and paved the way for further future experimentation in this field.
Introduction:
Little is currently known about the biology of vesicomyid bivalves occupying cold
seep communities in the deep ocean. The recent discovery of such communities in the
Monterey Bay Canyon and Fan Valley during ALVIN dives (Embley, et al., 1990) has led
to on-going research by the Monterey Bay Aquarium Research Institute and the Monterey
Bay Aquarium. Three species of vesicomyid clams are currently collected by the
remotely-operated vehicle (ROV) Ventana of the Point Lobos research vessel. These are
Calyptogena pacifica, Vesicomya gigas, and an as of yet unknown vesicomyid species
currently nicknamed "Sharpbutt," due to its sharply angled posterior end. All species are
known to carry endosymbiotic bacteria which utilize the hydrogen sulfide released at such
sites as a primary energy source in chemosynthesis (Childress et al., 1991). The ability to
routinely collect and maintain these clams in chilled sea water aquaria has permitted a
variety of studies.
In this project, two experiments were carried out in an effort to illuminate differing
aspects of the lives of these bivalves. Developmental work with time-lapse video was
carried out to create a system that would test for behavioral responses in the clams to
varying levels of hydrogen sulfide. Inconclusive results at the conclusion of the quarter
prevent the work from being discussed any further in this paper, but the background is still
of some foundational importance for the second experiment, so that information is still
mentioned here.
Observations around cold seep sites in the deep ocean have consistently revealed
burrow tracks surrounding and leading to the seeps, where scores of the vesicomyid clams
may be found (MBARI video footage record, 1993; Chuck Baxter, personal
communication; and Rosman et al., 1987). The clams leave the troughs behind as they
plow through the sediment to and around these sites which are rich in nutrients they
require for survival (Rosman). Rosman indicates that occurrences of vesicomyid clams in
varying densities are associated with varying gradients in pore-water chemistry and that
the movements of the clams suggests a dispersed nutrient source which requires
occasional active searching. While the trails observed come from various directions, the
clams are always found together in clusters, leading Rosman to deduce that the nutrient
source is confined to the areas of congregation and discontinuous in the surrounding areas
(Rosman, 1987; MBARI video footage, 1993). The film project was designed to test for a
specific relationship between the positional orientation chosen by cold seep clams and
varying levels of hydrogen sulfide being emitted from beneath the soil into the benthic
environment.
As the cold seeps these clams occupy are finite and small, the question arises of
how their developmental process enables newly developed clams to successfully find these
environments which are essential to their existence and yet seem scarcely larger than
specks in the vast expanses of the open ocean, assuming they ever leave them at all. The
egg buoyancy study was intended to shed some light on this aspect of deep-sea bivalve
development by focusing on the events taking place immediately upon the releasing of the
gametes. Research has shown that many factors, including advection, convection, and
other currents, tides, surf, density of biomass relative to the water, environmental
temperature and pressure, and predation, affect developmental success as well as where,
when, and how fast development occurs in the ocean (Woodin, 1991; Young, 1987; and
Mark Denny, personal communication). In the case of deep sea organisms such as the
cold seep bivalves, knowledge of these interactions immediately following the release of
the gametes can give crucial insights to what environmental conditions the fertilized
embryos go to and will later require for successful, complete development to occur. This
experiment examined the buoyancy of mature oocytes in an effort to determine if the eggs
of different species were consistently positively or negatively buoyant when initially
released into the cold seep environment. The whole process of either floating or sinking
upon release into a water environment for small objects relies both upon the frictional
resistance and the relative densities of the object and the seawater (Gross, 1987). Since
frictional resistance in an aquatic system is a product of the seawater’s viscosity and
therefore of the temperature, and since the temperature was controlled to remain constant.
it was expected that the frictional resistance would also remain constant. Therefore, like
gravity, it was disregarded as one of the natural elements an object would have to
overcome to become buoyant anyway. The key focus therefore, was the differences in
densities between the eggs and the surrounding seawater. Water density is easily
manipulated, being dependent solely on the water's salinity, temperature, and to a lesser
extent, pressure (Neumann and Pierson, Jr., 1966). For the purposes of this experiment,
the minute effects of pressure differences on density change were deemed negligible since
water is only slightly compressible, so only temperature and salinity were used to calculate
densities approximating those found in the environments from which the clams were
removed. While the resultant buoyancy rates would not be exactly equal to those at the
635m sites, they were deemed to be close enough to be indicative of what was happening
to the eggs in their natural environment. A device was subsequently constructed to meet
these needs precisely. The egg buoyancy chamber created and used in this experiment
allowed individual eggs to be observed under precisely simulated conditions of
temperature and salinity so that it could be determined if eggs predominantly floated or
sank upon release. Positive buoyancy was suspected, which would indicate travel to
another type of environment during the following embryonic and larval stages of
development before finally becoming a clam and settling back in a cold seep region. This
would also suggest the need for different environmental conditions and nutrients in order
for subsequent stages of development to proceed successfully.
Though tests were run using all three species of cold seep clams currently found in
the Monterey Bay, the only species for which complete data was available at the end of
the experiment was Calyptogena pacifica. Therefore, though some information was
retained concerning the "Sharpbutt" species, only the results of egg buoyancy studies on
C. Pacifica were discussed at length.
Rates of ascension or descension of oocytes were measured with the intent of
serving both as a preliminary indication of the extent of density differences between the
eggs and surrounding sea water and as a method to measure any differences or regularities
between individual eggs. Such rates have also been hypothesized to give an indication of
where the gametes go for future development (Young, 1987). Furthermore, they can
allow for a calculated estimate of how long it would theoretically take the traveling eggs
to reach different vertical environments in the ocean.
Materials and Methods:
The cold seeps in the Monterey Bay Canyon from which the clams were collected
were located by video camera navigation of the ROV, Ventana, from the Point Lobos
(Figure 1). All of the clams providing eggs used in the results of this experiment came
from the 635m site marked in Fig. 1. The ROV also collected and recorded data
concerning depth, pressure, salinity, and temperature changes during its dives (Figure 2)
The temperature and salinity values were extrapolated from the computer-recorded graph
in Figure 2 so they could be simulated in the experimental chamber. Temperature was
approximated to be 5.2° - 5.3° C. Salinity was estimated to be 34.28 parts per thousand
(ppt). The formula used to calculate the density at atmospheric pressure was taken from
the U.S. Naval Oceanographic Office's Handbook of Oceanographic Tables (1966, Table
1). The resultant density used to approximate that found at the 635m sites had a specific
gravity value of 27.11 (see Table 1 for explanation).
Once the parameters had all been determined, the next step was to simulate them.
The egg buoyancy chamber was designed to meet the needs of manipulable temperature
and salinity and yet providing a stable, current-free environment into which individual eggs
could be injected and observed for their reactions to the basic elements of different deep-
sea environments. The model used for this experiment was a prototype and underwent
later design changes. Rates of motion were measured against a vertically implanted ruler
using a stopwatch. Temperature was controlled by a recirculating cold bath. Salinity of
the internal chamber was increased to the required level of 34.28 ppt using a combination
of microfiltering ambient seawater (0.2 micron filter cartridge), salinometer measurements,
and the gradual addition of Instant Ocean synthetic sea salts to raise the salinity to the
correct level. Figure 3 provides a diagram of the egg buoyancy design and further
explanation of the temperature, salinity, and flow controls implemented in the design.
Continuous temperature control problems with the prototype required finishing the
observations in a cold room to ensure accurate maintenance of the low 5.2° C
temperature.
Eggs used in the experiment were acquired from the bivalves in a variety of ways
depending on the condition of the clams. One method was the seratonin injection method
recommended by Strathmann (1987). In the cases where clams did not respond positively
to the injections and spawning did not take place, the gonad was then removed by
dissection, the outer membrane teased away, and eggs either gently washed out (they
often were easily removed) or obtained by maceration through a 225 micron filter screen.
The eggs were stored in scintillation vials filled with the artificial deep-sea water in a 5° (
cold water bath until they could be used in flotation trials. The clams were also kept
constantly in these conditions, in individual beakers in the cold bath.
Six scintillation vials were sealed with eggs in them and observed over time in the
cold bath, to look for positional changes among eggs over time. This was done for both
Sharpbutt and C. pacifica. Data was lumped into sums for each species to avoid biases
due to individual clams and to determine the dynamics of the eggs when released in
groups. Observations were made after four hours, eight hours, and twenty-four hours.
Egg counts were translated into percentages and an average of the overall observation was
taken.
For the egg buoyancy tests, eggs were observed individually. Eighty-eight of over
150 trials were useable as data. Twenty-seven tests were of eggs with the cloudy mucus
still present., the rest were stripped by constant washing with the artificial deep-sea water
The holding vial was swirled before acquiring eggs in the syringe to evenly distribute the
eggs of various densities and get a random sampling. Each single egg was injected slowly
so that it entered the center of the chamber column neutrally and then ascended or
descended of its own accord and not due to the influence of a fast injection stream. The
egg was then timed as it proceeded to sink or rise, its time recorded every time it
progressed three centimeters. For all eggs, a general time limit of around 3 minutes was
given. If, after three minutes, the rate seemed to be constant but the egg had not yet
traveled the full distance of the ruler, recording was ceased for that test. However, if the
rate seemed to be still changing, testing was continued until either the egg reached either
end of the chamber or a constant rate was eventually reached. Rates were deemed
constant if they were the same for two consecutive measurement points.
Results:
The results obtained from the twenty-four hour observations of the eggs stored in
scintillation vials were put into bar graph form for easy interpretation in Figure 4. After
four hours, well over 90% of the eggs from C. pacifica were floating. Close to half of
these eggs in every vial were contained in the translucent mucus that accompanied the
eggs during spawning, which floated in a single sticky mass in every case. Only an
average of 4% of eggs had sunk at this time, and no mucus accompanied these. After
eight hours, the percentage of eggs floating freely had risen to over 60% from the 48%
observed at four hours. In all vials, the mucus had become cloudy and coagulated, and it
had either sunk completely to the bottom or was hovering just over the bottom. The
percentage of eggs contained in the mucus had dropped from close to 50% observed at
the four hour mark to about 30% at the eight hour mark. These eggs, trapped in the
sticky mucus, were now recorded as sunken rather than buoyant. At the twenty-four hour
mark, these effects remained and merely became slightly more pronounced; the mucus
material in every vial remained on the bottom and appeared to be shriveled and much
smaller in size, a greater percentage of eggs floated near the surface of the vials, free of
mucus, and the percentage of sunken eggs that were free of the mucus had decreased
Finally, in four of the six vials the shriveled cloudy mucus mass was now beginning to
break apart and dissolve.
The results of egg buoyancy tests were summarized as two separate tables in
Table 2, one for eggs in the presence of the mucus material, one for eggs that had been
filtered and cleaned free of mucus. For eggs tested in the presence of the mucus, 100%
were positively buoyant under the simulated cold seep conditions. 75.41% of the eggs
that had been freed of mucus were positively buoyant (46 of 61), while 3.28% of them
sank and 21.31% were neutrally buoyant (Table 2)
Average rates also differed between the two groups. Table 2 shows that eggs in
the presence of mucus had an average rate of 0.273 cm/sec (SD 0.1997 cm/sec) while
filtered, mucus-free eggs traveled at an average 0.03324 cm/sec. (SD 0.03116 cm/sec)
Note that while all of the eggs in the presence of mucus were positively buoyant, some of
the cleaned eggs were neutral and even negatively buoyant, serving to lower the average
rate somewhat. A comparison of the ranges of buoyancy rates between the two groups
shows also that the eggs in the presence of mucus, which were all positively buoyant, also
covered a much greater distribution of rates, 0.69, than eggs that had been filtered and
isolated, whose range of rates was 0.1566.
To illuminate the trends in rates of eggs in both conditions, Figure 5 shows in
graph form how average buoyancy rates of both groups of eggs varied with respect to
increasing height of the buoyancy chamber. The average rate at each height for eggs with
the cloudy discharge steadily decreases from over 1 cm/sec at the 3cm. mark to around
0.3 cm/sec by the 15 cm. mark, while the average rate of the filter-cleaned eggs appears to
remain fairly constant at less than 0.1 cm/sec along the entire distance of the tube. Not
enough data was collected to gauge the average rate for this group beyond the 12 cm.
mark. Only positively buoyant egg data was compared in this graph to give an accurate
comparison of differences caused by the presence and absence of the mucus discharge
Discussion and Conclusions:
There were many holes in the methods of data collection in this experiment and in
the data itself which prevented it from being strong and conclusive evidence, but a few
trends were able to be positively identified which can serve as the basis for stronger
hypotheses and lead to future experimentation. To begin, the one part of this experiment
that strong conclusions can be made about is based on the information gathered
concerning the effects of the mucus, and it is not even clear that this would ever exist in a
normal spawning situation. It clearly accompanied the eggs during the seratonin injections
and dissections. It therefore may be the product of unnatural situations only and never
occur in normal conditions. When the mucus is present, however, it is increasing both the
percentage of buoyant eggs and the rates of ascension. In the presence of the cloudy
mucus, close to 100% of the eggs were at least initially positively buoyant as shown in
both Fig. 4 and Table 2. When this material was not present, only approximately 75% of
that batch of eggs was ever positively buoyant. Figure 4 shows that the mucus
consistently began to sink and coagulate by eight hours, which increased the percentage of
eggs that ended up on or near the bottom of the experimental vials. The mucus also had
an obvious affect on the movement of the eggs. This is depicted in the graph in Figure 5.
which displays a trend indicating strongly that the demographics of eggs released by the
clams are significantly different as a result of the presence of the mucus.
If it does turn out that the mucus material is normally present, then based on the
observed effects its presence has, a few speculations can be made. The change in
buoyancy could be due to the gradual loss of some positively buoyant chemical into the
external seawater environment over time, such as ammonia. The presence of the mucus
could be serving one of two possible purposes. Either it is providing a means for
developing embryos to return to the benthic environment and is therefore an aid to
development, or it is just by chance dragging some of the developing eggs back down to
the bottom greatly before their time and is hence a hindrance to their chances of survival
If the developing embryos do indeed require a different environment for development, as
has been hypothesized by many different researchers (Young, 1993), then this cloudy
material could either help, in the case of the increased ascension rates, or hinder, as in the
case of drawing trapped eggs back down to the bottom before they had fully utilized other
required conditions. Based on the average ascension rates (Table 2), it was estimated that
eggs floating within the accompanying mucus would take a mean of 2.5 days to reach the
surface, while eggs floating freely could at best climb about 50 meters in two days (though
the range of distribution is greater, including some eggs that wouldn’t rise at all in the
absence of the mucus)
So far, developmental experimentation at the Monterey Bay Aquarium and by
MBARI researchers on these cold seep bivalves has shown that it takes about 6-7 days to
get close to the larval stage (+ 64 cells) under stable 6° C conditions in the lab. While
increases in temperature that accompany ascension seem to speed up this process (Young,
1993), it is not known how fast. However, this change could be required if the larvae turn
out to be lecithotrophic and have a limited internal energy supply, as many researchers
suggest (Gage and Tyler, 1991). In six days the average free eggs would have climbed
over 150 meters, taking them to slightly warmer waters (+ 6° C, as opposed to the 5° C
native to the clams) with a slightly lower salinity (approx. 34.2 ppt). These conditions are
not much different from the initial conditions in which the eggs are released, but food
conditions, currents, turbulence and radiation exposure conditions can be. Therefore, the
presence of the mucus would have greater significance since transportation in its presence
would be much more speedy
The buoyancy tests only produced enough data to indicate a few trends, but
nothing can be concluded. Tests performed with clean eggs indicate a broad range of
densities among the eggs, between being more dense than the sea water to being less
dense. Neutral eggs suggest a condition of homeostasis (see Table 2). The risers
themselves covered a wide range of velocities, so densities evidently vary greatly and do
not seem to favor a norm. The fact that the standards of deviation for both average
buoyancy rates are very large indicates that the means do not give any strong indication of
normalcy in either experimental group. If the two tables in Table 2 are compared, it can
be seen that this is less so for the mucus group, especially since all the eggs in this group
floated. While much could be speculated about the implications of this information,
nothing can be concluded due to the scarcity of data available. More work needs to be
performed for conclusions and further speculation to be made.
Aside from the curious presence of the mucus, a few other factors exist which
might have skewed data and therefore added to the possibility of there being misleading
trends. First of all, the clams that were used in this experiment had been in captivity for
anywhere between two weeks to six weeks. Capture methods had not been perfected
during the time of this experiment, and clams often suffered from deteriorating health and
would eventually die after having been in captivity for a few months. The different
conditions under which they were maintained could have affected the physiology of the
clams and the physical makeup of materials produced by the animals, such as the eggs in
the females. The extent of any possible osmotic changes that may have occurred inside
the clams is not known, but this possibility exists
Second, the egg buoyancy chamber used for the experiment was a prototype which
had not been perfected, so many problems had to be dealt with during the course of the
experiment, such as moving the system to a cold room when it became evident that the
prototype was not adequately maintaining uniform cold temperature when at room
temperature. This weakens the scientific accuracy of the project. A new design has since
negated this problem.
For the future, problems with sickly clams, a faulty egg buoyancy chamber, and the
late discovery of the elusive mucus will not exist. This should allow for uninhibited data
collection to accurately determine predominant trends for the eggs of all three of the cold
seep species of the Monterey Bay and elsewhere. Besides determining buoyancy trends.
rates, and ultimately egg densities, future experiments can test for rate differences with
increasing temperatures to determine if there is a range of sea water densities at which
eggs become neutrally buoyant or stop ascending. It should also be determined whether
different stages of development cause changes in buoyancy rates or densities. Then
perhaps indications will be given of where the eggs belong in the vast oceans, and the
mystery of development of these bivalves can be further unraveled. For now, it seems
indicated by the trends that the developing embryos are bound for a pelagic development
rather than a benthic one. More work is definitely needed. The key to understanding the
development of such mysterious deep sea organisms appears to lie in first understanding
the path of travel followed by the developing gametes, indicated by density differences and
flotation rates. From there, regions where further development occurs may be pinpointed
and later stages of development identified, allowing progress to continue in the study of
the development of cold seep bivalves.
Acknowledgments
The three men without whom I would never have developed such a project are
Chuck Baxter, Jim Barry, and Chris Harrold. They were the key idea men in this project
Towe all three a great deal in giving me developmental direction and inspiration, both with
this project and in learning about the process of research in general. To John Lee, thanks
for helping me break ground with development of the prototype of the egg buoyancy
chamber, which I finally worked all the bugs out of during the following summer. Of all
the people from my spring class, I probably owe the MOST thanks to the following
people, on whom I exacted the greatest toll when I thought I’d “lose it" near the end: to
the TA, Molly C., who kept me from snapping before my presentation after I spent the last
11 days and 10 nights constantly awake and frantically trying to acquire and interpret
fresh, unbiased data; to the library folks, Alan and Susan, for their patience with my mess
in the library when my project "crashed" right at the end of the quarter; and, most of all, to
Chuck Baxter who was and continues to be my inspiration. He convinced me of the
promise of this project, so well in fact that I stuck myself with it through the following
summer at the Monterey Bay Aquarium until at last I had to tear myself away and go back
to school; he effortlessly put me back on track when I was lost, so wise is he, he reminded
me that beer CAN calm you down when you need to relax; and, he waited patiently to be
truly retired from responsibilities to Stanford for once and for all while I spent the next
year over-committed to academics and the rest of the world and attempted to get out of
Stanford myself. Like many countless others before me but none officially after me,
Chuck gave me inspiration and direction as a professor in marine biology in and outside of
some awesome classes. He will never cease to inspire those he interacts with. Good luck
to you in your new endeavors, Chuck! And thanks to all.
Works Cited
Childress, J. J. et al. "Sulfide and carbon dioxide uptake by the hydrothermal vent clam,
Calyptogena magnifica, and its chemoautotrophic symbionts
Physiological Zoology. 1991; 64: 1444-1470.
Embley, R. W. et al. "Geological setting of chemosynthetic communities in the Monterey
Fan Valley system." Deep-Sea Research. 1990; 37(11): 1651-1667
Gage, J. D., and Tyler, P. A. Deep Sea Biology: A Natural History of Organisms at the
Deep-Sea Floor. NY: Cambridge U. Press, 1991.
Gross
M. Oceanography, a View of the Earth (fourth edition). NJ: Prentice-Hall, Inc.,
Neumann, G. and Pierson, W., Jr. Principles of Physical Oceanography. NJ:
Prentice-Hall, 1966.
Rosman, I., et al. "Epifaunal aggregations of Vesicomyidae on the continental slope off
Louisiana." Deep-Sea Research. 1987; 34(11): 1811-1820.
Strathmann, M. Reproduction and Development of Marine Invertebrates of the Northern
Pacific Coast. WA: U. of Washington Press, 1987.
Handbook of Oceanographic Tables (special publication). Wash. D.C.: U.S. Naval
Oceanographic Office, 1966.
Woodin, Sarah Ann. "Recruitment of infauna: positive or negative cues?" Amer. Zool.
1991; 31: 797-807.
Young
Craig, and Cameron, J. "Laboratory and in situ rates of lecithotrophic eggs from
the bathyl echinoid Phormosoma placenta. Deep-Sea Research, 1987; 34(9):
1629-1639
Craig, and Tyler, Paul. "Embryos of the deep-sea echinoid Echinus affinis require
Young
high pressure for development." Limnol. Oceanogr. 1993; 38(1): 178-181.
Legend for Figures and Tables
Figure 1: Map of where cold seep clams were found in the Monterey Bay
Canyon. Collection sites are indicated by an
Figure 2: Dive data from the ROV, Ventana, aboard the Point Lobos (MBARI
research vessel). Recorded during March 19, 1993 collection of C. pacifica in the Monterey Bay
Canyon. Salinity, oxygen, depth (directly related to pressure) and temperature were all recorded.
Table 1: Density tables from the U.S. Naval Oceanographic Office's Handbook of
Oceanographic Tables, 1966, along with an explanation of calculations and units.
Figure 3: Diagram of egg buoyancy chamber prototype. The outer chamber and
inner chamber are isolated from each other. The outer chamber circulates water from the cold-
water bath recirculator, controlling the temperature of the inner chamber. The inner chamber is
accessible from the outside, allowing manipulation of the salt content and water density, and
allowing the water to be cleaned from time to time, when too many eggs were inside. The syringe
port is the site of egg insertion.
Table 2: Table of data for egg buoyancy tests, in two parts. The first box contains
data for eggs tested in the presence of the cloudy mucus material that accompanied them during
spawning. The second box contains data for eggs that were filter-cleaned and tested clean
Figure 4: Bar graph depicting ratios of eggs in different states as observed in
scintillation vial experiment. Floating eggs are the bottom two groups at 4 hrs. and the bottom
group at 8 and 24 hrs., eggs that sank are the top group at 4 hrs. and the top two groups at 8 and
24 hrs. Error bars give an indication of relevancy of changes between times.
Figure 5: Comparison of average rates vs. heights between filtered and non-
filtered eggs of C. pacifica. While a difference in trends exists, note that these averages are
misleading, since both groups had such a large variation of rates. The filter-cleaned eggs moved
too slowly for enough data to be collected for a relevant point at 15 cm. Only the heights appear
on the graph which allow a direct comparison to be made.
Figure 1
SANTA CRUZ
Copitolo
SOOUel Cov ooine.

ote



PACIFIC
GROVE

Vas
lo Selvo Beoch

Marino
Fiquse 2
Oxygen (ml/1) ++++
emperoture (C)

54
J-





200
s..
5
400
60
—

-635
L3
800
o
2
33.0
33.5
34.0
157 345
Salinity (PSU) -
Beam Attenuation (/m) *
File: 07893r02 (preliminary data)
Dive data from the ROV, Ventana, aboard the Point Lobos
(MBARI research vessel). Recorded during March 19, 1993
collection of C. pacifica in the Monterey Canyon.
16
Table 1
DENSITI (g.)
Salinity 30.00%/00 to 39.99%00
.
T. C.
T. •C.
T. •C.
-2.00
2u.15
23.83
7.37
L.07
23.16
.820
-1.75
.82
.18
.1
.15
.15
.7910
.81
.8100
.80
-1.13
24.13
7.52
23. ul.
.13
-0.71
21.12
.8090
1.50
23.75
.12
.60
3

-0.31
.70
21.11

.7930
.82
.0
.8070
-0.08
.80
.10
.39
90
.96
.75
0.18
21.09
.8050
8.0
5.00
23.7u
23.37
0.12
11
.36
.09
0.61
24.07
.19
.18
.35
.7910
.80l0
0.85
.27
.25
.06
.3
.70
.33
1.0
16
.69
21.05
.39
.32
.8020
.l6
.21
.31
23.68

5.56
.03
.65
.67
8.53
23.30
1.58
.73
60
21.02
.7900
.29
.82
.01
.8010
65
.67
.28
24.00
.91
.27
.61
20
EXAMPLE OF COMPUTATION
Given a temperature of 15.70° C. and a salinity of 36.47%. compute the «, value.
1. Select the salinity interval of 30.00 to 39.99%.
2. In column one, find the temperature interval in which 15.70 falls (always use the
loicer limit of the interval). The lower limit is 15.69° C.
3. Entering column one at 15.69° C. read the corresponding value of 22.00 in column
two. This is the correct «, value for the base of the salinity interval, that is, for a salinity
of 30.00%. and temperature of 15.69° C.
4. To find the correct v. value for the given salinity of 36.47%., multiply the desig¬
nated f-factor in column three (.7680) by the last three digits of the given salinity (6.47),
observing decimal places, and add the value obtained to the base value 22.00
5. Round the value obtained (26.96896) to two decimal places. ANSWER 26.97.
Thus: Given 15.70° C. and 36.47%. S.
Frem table for Salinity 30.00 to 39.99%., enter column one at lower limit of tem¬
perature interval (15.69) :
Obtain base
f-factor
last three
ralue in
of column digits of
three X given S.
column two +
6.47
22.00
7680
26.968960 (round to two decimal places) ANSWER 26.97
(U.S. Naval Oceanographic Office, 1962)
.7860
.7850
.7810
.7830
EGG BUOYANCY CHAMBER DESIGN
Figuc 5
18 rubber stopper
thermometer / syringe access
inner egg-testing chamber,
salinity control

outer circulating chamber.

— temperature control
insulating

counter-current
input
30 cm. scale for rate
determination

18-gauge syringe needle
(press-fitted through ceramic
for water-tight seal)


disposable syringe



output back to
T
temp.-controlled circulator
25"
L
1.5"
2.5
13.1
Table 2: EGG BUOYANCY TEST RESULTS AND DATA
Eggs with cloudy discharge
Number of eggs tested
IMEAN BUOYANCY RATE
Standard Error
Standard Deviation
Variance
Range of rates
Minimum ascension rate (cm/sec)
Maximum ascension rate (cm/sec)
percent positively buoyant: 27/27
Eggs fittered and isolated
Number of eggs tested
MEAN BUOYANCY RATE
Standard Error
Standard Deviation
Variance
Range of rates
Minimum ascension rate (cm/sec)
Maximum ascension rate (cm/sec)
46/61
percent positively buoyant:
2/61
percent negatively buoyant:
13/61
percent neutral
"neutral buoyancy based on 3+ min. observations following egg insertion
27
0.273
0.0384
0.1997
0.0398
0.69
0.06
0.75
100%
0.03324
0.003989
0.031155
0.00097064
0.157
-0.018
0.14
75.41%
3.28%
21.31%
Figure 4: Average buoyancy characteristics for 6 vials of
vesicomyid bivalve eggs over time
100%
90%
80%
70%
% sunk with mucus
60%
%sunk alone
50%
% floating with mucus
40%
%floating alone
30%
20%
10%
time (hrs.)
Figure 5: Comparison of average rates vs. heights between
filtered and non-filtered eggs of C. pacifica
1.2 -

06
eggs with cloudy discharge
204
0.2
filter-cleaned eggs

0
3
height (cm)
15