ABSTRACT: Mytilus californianus dominates the rocky mid-intertidal zone along much
of the West Coast of North America from Alaska to Baja California. Thus, it has
important effects on community structure. Previous work has failed to identify genetic
differences among populations along this latitudinal gradient. However, some differences
in morphology have been described. A preliminary study showed that mussels from
Central Oregon grew significantly faster than those from Central California when
transplanted to sites in either state. My study investigated physiological differences in
populations of M. californianus from Oregon and California. In February, mussels were
transplanted to California from Oregon and California. In May, additional mussels were
freshly collected from the original populations. Gill respiration rates and malate
dehydrogenase (MDH) activity were examined to compare metabolic rates of individuals
in these populations, and determine if differences were intrinsic or transitory effects of
acclimation.
No significant differences were found in respiration rates or MDH activity
between the two populations of mussels, both for field acclimated and freshly collected
groups. Although overall field growth was low, there was suggestive but inconclusive
evidence that transplanted mussels from Oregon grew significantly more than California
mussels during the February to May period. These results do not rule out either an
acclimation effect or intrinsic differences between these populations. Because the Oregon
waters were slightly colder (by 2.5°C) during the ten weeks prior to the transplantation.
acclimation of the Oregon mussels may explain the growth difference. Alternatively.
there could be intrinsic differences in growth potential between the two populations. In
either case, differences in respiration rates and MDH activity were either too small to be
detected, or may not be directly correlated with growth activity. Although physiological
differences were not observed, there appear to be some differences among these mussel
populations such as the average dry weight of gills from Oregon mussels was 16.9% less
than the average weight of similarly sized California mussels.
INTRODUCTION
Although intertidal and subtidal systems have been studied extensively, very little
is known regarding latitudinal variation in marine populations. Considerable research has
found physiological and biochemical variation in organisms across their geographic range
(Walsh and Somero 1981, Hochachka and Somero, in press), but little is known about
how these responses to local temperature affect populations and communities. In addition
to differences caused by the latitudinal temperature gradient, populations may vary
genetically. The life histories of most marine species include planktonic stages, and thus
high gene flow among populations is expected. However, current studies suggest that
larval retention and genetic differentiation may be more common than previously thought
(Warner et al. 2000).
Recent work has found significant differences in growth between mussels from
populations of Mytilus californianus. During the summer of 2000, Eric Sanford
transplanted groups of mussels from Central Oregon and Central California to both
Oregon and California. The results showed that Oregon mussels grew faster than those
from California at all sites independent of location. In this study, I investigated whether
differences between populations were the result of acclimation or intrinsic effects.
The California mussel, M. californianus, is a common marine invertebrate in the
rocky mid-intertidal zone (Gosling 1992). Its distribution spans the West Coast of North
America from Alaska to Baja California, and often can dominate very wave exposed
areas (Ricketts et al. 1985). M. californianus has been shown to limit biodiversity of
sessile marine invertebrates through competition for space (Paine 1966). However, the
mussel bed creates habitat for other marine organisms. Thus, this species has strong
impact on community structure in the intertidal zone.
Because M. californianus is an ectothermic species, its body temperature is
dependant upon its environment (Helmuth 1999). Therefore, physiological processes
could be greatly affected by ambient temperatures. If enzymatic activities of animals are
measured at the same temperature, the organisms from colder temperatures will often
have higher activities and metabolism than their equivalents from warmer environments
(Hochachka and Somero, in press). Thus, the metabolic activities of the organisms at
their respective native habitats will be similar. Moving an organism from colder to
warmer waters may cause physiological processes to speed up until the animal has
acclimated to the new environment.
Because the only direct way to quantify metabolism is by difficult calorimetric
methods, indirect methods generally are used to measure metabolism (Schmidt-Nielsen
1997). The most used method to obtain metabolic rates is to determine oxygen
consumption. Quantifying activity of an ATP generating enzyme is another way to
measure metabolism. Metabolism has been correlated with growth (Frandsen and
Riisgard 1997), reproduction (Smaal et al. 1997), seasonal variation (Hatcher et al.
1997), age (Sukhotin and Pörtner 2001) and many other processes.
Despite the broad distribution of M. californianus, research has shown few
significant differences among populations of the mussel. Grant Pogson at University of
California, Santa Cruz has not found significant genetic differences among M.
californianus populations (Sanford pers. comm.). Levinton and Suchanek (1978) also
found minimal genetic variation in M. californianus along 3000km of the North
American West Coast. However, M. californianus is known for having variation within a
population. Although few growth studies have been done on M. californianus, the rate of
shell growth has been shown to vary with age, sex, temperature and food concentration
(Coe and Fox 1942, 1944; Fox and Coe 1943). Dehnel (1956) examined growth in the
field of mussels from different latitudes, and found significant variation with mussels at
his most southern site having the largest growth rate. Unfortunately, mussels at these sites
were from different tidal heights, which probably affected growth more than water
temperature. Pickens (1965) showed some temperature compensation for the heart rate of
M. californianus at colder temperatures. Mussels acclimated to new temperatures in six
weeks or less, but this was dependant on mussel size.
Additionally, morphological differences between populations have been
researched. Environmental conditions (e.g. wave exposure) affect shape and shell
thickness, and the thicker shelled mussels may grow slower than thinner ones (Fox and
Coe 1943; Coe and Fox 1944). Rao (1953) found an increasing proportion of shell weight
to soft tissue weight as latitude increased.
This study investigated whether differences in growth between populations of M.
californianus from Central Oregon and Central California occurred during the winter
period. This research also examined metabolic rates by comparing respiration and malate
dehydrogenase (MDH) activity between these two populations. Additionally, some
aspects of mussel morphology were evaluated.
MATERIAL AND METHODS
Collection and Maintenance of Specimens
In February 2001, mussels (4.5-5.Scm in shell length) were collected from the
lower limit of wave-exposed mussel beds at Mal Paso Creek, California (36°33'N
121°56’W) and Fogarty Creek, Oregon (44°50’N 124°03’W). Mussels from each site
were transplanted by Sanford into 20 x 20 cm Vexar"M mesh cages in the low-intertidal
zone at two wave-exposed sites: Soberanes Point, California (36°27’N 121°56’W) and
Hopkins Marine Life Refuge, California (36°37.3N 121°54.3’W). Each of the six cages
contained 20 mussels from both sites of origin. A small notch was filed into the growing
lip of each mussel shell to allow the measurement of growth and to identify the source of
the mussels (Oregon=1 notch, California=2 notches). In May 2001, transplanted mussels
(n=2 per site of origin per cage) were collected at Soberanes Point and put into seawater
tanks at Hopkins Marine Station. During the same period, mussels were freshly collected
from Mal Paso Creek and Fogarty Creek (n-30 per site) and stored in the same seawater
tank.
I quantified respiration rates of and enzyme activities in the gills of these mussels.
For each mussel, length and growth (of the transplants) were measured. 1 then dissected
the mussel and removed both gills, which were washed in 0.22um filtered seawater
containing the antibiotics (Penicillin-G and Streptomyocin each at a concentration of
0.15mg/L). For each mussel, one gill was used to obtain a respiration rate and the other
was used to determine the activity level of malate dehydrogenase MDH, an enzyme of
the Krebs citric acid cycle and the anaerobic glycolytic pathway.
Respirometry
Before the respiration trial, I put the gill in a 100mL beaker with filtered seawater
and antibiotics and placed it in a 15°C water bath. The oxygen microelectrode (model
MI-730, oxygen meter model ÖM-4, Microelectrodes, Inc., Bedford, NH) was zeroed by
submersing it in an oxygen-free solution of O.OIM NaB saturated with NaS crystals. The
electrode was then calibrated to full oxygen saturation in the solution of filtered seawater
and antibiotics that was gently bubbled with an air pump.
Respiration was measured in a water-jacketed 14.4mL chamber (Fig. 1). The
microelectrode entered the chamber through a threaded hole in the top. The water-jacket
surrounding the respiration chamber was connected to a water bath set to 15°C and the
whole device sat upon a stir plate. The gill was sandwiched between two layers of nylon
mesh and placed on a perforated plastic platform over a magnetic stir bar. I carefully
sealed the chamber and removed all air bubbles before beginning the trial. Using the
Powerlab unit (8sP ADInstruments, Mountain View, CA) and the Powerlab Chart
Program, I measured the decline of oxygen saturation for 30 min, removed the gill, and
ran a control for another 10 min. Äfter the run, I weighed the gill by blotting both sides
with a Kimwipe'" so that respiration rate could be normalized by the mass of the gill
tissue. 1 determined gill respiration rates in at least six mussels from each treatment (n-6-
7 per treatment).
1 calculated respiration rates from the slope of the decline in oxygen for 20 min
after an initial 10 min period. Because the slope used was after the first 10 min, control
runs were not subtracted out since they usually were made during the initial 10 min of the
run when there was often noise in the reading. This slope was normalized by
incorporating the solubility of oxygen, the volume of the chamber and the weight of the
gill. I used the following equation to get the rate in umol O2/sec/gram of gill tissue: (the
volume of the chamber) x (slope/100) x (solubility of oxygen at 15°C, latm, 34%00
salinity of seawater). I performed a single factor Analysis of Variance test (ANOVA) to
determine whether oxygen consumption differed among the four groups.
MDH Biochemical Assay
MDH activity was quantified in the other gill from each mussel used in
respiration, and from three or four more mussels per treatment (n=10 total per treatment)
The gill was weighed and then homogenized (Duall, Kontes Glass Co., Vineland, NJ) on
ice by hand and diluted 5x in 200mM imidazole buffer, pH=7.0. I then transferred this
solution into a 2mL Eppendorf tube and centrifuged it at 5°C and 1400Orpm for five min,
1 mixed 50mL of 200mM imidazole buffer (pH=7.0) in an Erhlenmeyer flask with
0.0054g of NADH (final concentration of O.15mM) and 0.0014g of oxaloacetate (OAA)
(final concentration of O.2mM). This solution was kept on ice and in the dark whenever
possible to minimize degradation of NÄDH. A spectrophotometer (UV-1601, Shimadzu
Scientific Instruments, Inc., Columbia, MD) with the Kinetics computer program was
used to read the activity of the enzyme. The spectrophotometer was zeroed using the
buffer before assays were started. 3mL cuvettes with 2mL of the cocktail were
equilibrated in a 15°C water bath. Using a 25uL Lang-Levy pipette, I transferred an
aliquot of the sample to one of the pre-equilibrated cuvettes in the spectrophotometer,
stirred the solution vigorously for five seconds, and then recorded the activity for 30 sec
(n=5 replicates per gill).
To prepare the measurements for data analysis, I first ensured that the MDH run
contained no electrical spikes for at least 15 sec. I calculated the enzyme activity from the
change in absorbance/min for 25 sec. To determine the activity of the enzyme the
following equation was used: (Aabs/min x volume of gill homogenate)/(s of NADH).
where s equals the extinction coefficient. To determine the activity in umol
OAAlmin/gram of tissue the activity was multiplied by 200 because 5mg of tissue were
put into the cuvette. I performed a single factor ANÖVA to test whether differences in
activity existed among the four groups. Respiration rates were compared to the MDH
activity using a regression analysis.
Morphological Measurements
Morphological measurements were also made to investigate variation between the
Oregon and California mussels. I measured the shell length, width and total thickness of
freshly collected mussels from Oregon and California (n=10 per population). I also
measured both wet and dry weights of the gills. Prior to weighing, wet gills were blotted
(see above), and dry weights were measured after gills had been dried at 70°C to a
constant weight (approximately 48 h). I performed analyses using t-tests and regression
analysis to determine if any differences between populations were significant.
Field Growth Measurements
The growth of transplanted mussels was quantified in late May in the field at both
Soberanes Point and Hopkins Marine Life Refuge. New shell added beyond the notch in
the growing lip of each mussel was measured (+0.01) using digital calipers. Six cages at
Soberanes Point and three cages at Hopkins Marine Life Refuge were sampled (n=30-40
mussels per cage). Using t-tests, I tested whether growth per 100 d differed between
mussels from Oregon and California.
Temperature Loggers
Temperature records were obtained from mid-intertidal data loggers (Optic
StowAway, Onset Computer Corp., Pocasset, MA) at Soberanes Point, Hopkins Marine
Life Refüge, and Fogarty Creek. Data loggers were put in the field over three months
before the February transplantation and were collected in May after samples were taken. I
used the temperatures from two hours before to two hours after each high tide to calculate
the mean high tide temperature. These data were used to estimate the acclimatization
temperature of the mussels used in this study. In addition, data on temperatures while the
transplants were in the field were collected. Data were analyzed using a t-test to
determine if the sites had different temperatures.
RESULTS
Four treatment groups were compared: freshly collected from Oregon and
California, and field-acclimatized from Oregon and California (transplanted for 10 weeks
to Soberanes Point).
Respirometry
The respiration runs showed great variability among individuals within the same
treatment group (Fig. 2). Mussels in all treatments had similar respiration rates of
approximately 0.0012 +0.0001 umol O2/sec/gram of tissue. There were no significant
differences between the Oregon and California mussels, either freshly collected or field
acclimated (Table la, ANOVA, p-O. 413).
MDH Biochemical Assay
Similar to the respiration results, the MDH activity showed no significant
differences among the treatment groups (Table 1b, ANÖVA, p-O. 831). There was
considerable variability among individuals, but replicates for each individual were very
similar. The mean activity for all treatments were very similar at 0.143+ 0.005 umol
OAA/min/gram of tissue (Fig. 3). There was no correlation between respiration rates and
MDH activity levels (Fig. 4, p-0.194, R“=0.075).
Morphological Measurements
The thickness (t,=-0.828, df=18, p=0. 419), length (t,=-0.263, df-18, p-0. 796),
and width (t,=1.23, df=18, p=0. 235) of the shell were not significantly different between
Oregon and California mussels. However, despite the similar size of mussels, the gill dry
weight of Oregon mussels was 16.9% less than that of California mussels (0.0190g vs.
0.0229g, respectively; t,=2.66, df=18, p=0. 016). Gill wet weight was significantly
correlated with gill dry weight (Fig. 5, p=1.68E-06, R“=0.729). In addition, I noticed that
the Oregon mussels had pale gills while the California mussels' gills were bright and rich
in color (Fig. 6).
Field Growth Measurements
At both sites, the mussels from Oregon grew faster than those from California
(Fig. 7), although differences fell just short of statistical significance. At Hopkins Marine
Life Refüge, the Oregon average growth was 1.72mm/100 d while for California mussels
it was 0.952mm/100 d (t==-0.196, df=4, p=0.061). Similarly, at Soberanes Point, Oregon
mussels tended to grow faster than those from California (0.52mm/100 d vs. 0.31mm/100
d, respectively) although growth was much lower than that at Hopkins, and the difference
was only marginally significant (t,=-1.739, df-10, p-0.056).
Temperature Loggers
Water temperatures during the 10 weeks prior to the February transplantation of
the mussels were 2.5°C cooler at Fogarty Creek than at Soberanes Point (Fig. 8, t,-30.04,
df-292, p=2.64E-91). In contrast, water temperatures during the 10 weeks prior to
collection of fresh mussels in early May were only 0.7°C cooler at Fogarty Creek (Fig. 9.
ts=1.969, df=254, p=4.94E-04). Mussels transplanted to Soberanes Point experienced
water temperatures 2°C cooler than those at Hopkins Marine Life Refuge during the 10
weeks of growth (Fig. 9, t,=15.83, df=254, p=9.48E-40).
DISCUSSION
This research showed that during the winter, growth of Oregon and California M.
californianus was very slow. The difference in mussel growth rate was nearly significant
between the populations (p=0.05-0.06), but the lack of significance in rates may be due to
small sample sizes and low resolution from little growth. In comparison with a similar
study during the summer (Sanford, unpub. data), the summer growth was over 3.5 times
faster than the winter growth for these populations of M. californianus.
Acclimatization has been hypothesized as one of the reasons that mussels from
Oregon grow faster than the mussels from California. During the February
transplantation, the Oregon mussels were coming from water that was 2.5°C colder
(Fig. 8) so that the difference in growth could have been due to acclimation. However,
Sanford's study in 2000 that showed a dramatic difference in growth, actually had
Oregon mussels being transplanted to a colder climate than what they had experienced
(due to earlier onset of spring upwelling in Central California), suggesting that the
differences in growth could not have been due to acclimatization.
Another interesting finding of my study was that mussels grew faster in Hopkins
Marine Life Refuge than ones at Soberanes Point. Hopkins Marine Life Refuge is in
Monterey Bay whereas Soberanes Point is on the open coast, where water temperatures
are often over 2°C cooler (Sanford, unpub data).
Because age can play a role in growth rate, it may also be a factor in why Oregon
mussels seem to grow faster. Younger mussels grow faster than older mussels (Morris et
al. 1980, Sukhotin and Pörtner 2001). Therefore, if mussels grow faster in Oregon
because of another factor such as food availability, then although similarly sized mussels
were transplanted, those from Oregon may have been younger. Thus, differences in
growth may be the result of the difference in age rather than a true difference between
populations.
The suggestive difference in growth was not reflected in the physiology of these
organisms. Respiration and MDH activity results clearly showed no significant
differences between Oregon and California mussels during winter (Fig. 2 and Fig. 3).
However, because the growth was minimal, the differences in metabolic rates may have
been muted and difficult to detect with relatively small sample sizes. Respiration and
MDH activity showed no correlation (Fig. 4). This may be because MDH plays a role in
both aerobic and anaerobic ATP generation whereas oxygen consumption only reflects
aerobic metabolism. In addition, it is possible that respiration and MDH activity may not
be linked with growth in M. californianus.
Despite the similarities in physiology, there were some interesting morphological
differences. The Oregon gills were much lighter in pigmentation than the California gills
(Fig. 6), perhaps due to an environmental factor (e.g. diet) or perhaps indicating intrinsic
differences between the populations. In addition, for similarly-sized mussels, the Oregon
gill was significantly smaller than the California gill. This, too, could reflect greater
water-column food concentration in Oregon (such that the gill needs less surface area), or
it may be an intrinsic difference between the populations.
The larval biology of M. californianus suggests minimal variation between
populations along a latitudinal gradient. The pelagic larval stage of the M. californianus
veliger lasts about nine days (Strathmann 1987). Because of the short pelagic larval stage,
it seems unlikely that the larvae would be able to travel significant distances along the
Northern American West Coast. Thus, populations of M. californianus along the West
Coast could have reduced gene flow, and differences in populations especially because of
adaptations to a particular environment seem possible.
One factor this research did not address was possible differences in air
temperature and heat stress between sites. The mussels were normally exposed for about
half of the day. Air temperature in Oregon would most likely be colder, but the effects of
air temperature on mussel growth, respiration, and MDH activity are unknown. However.
air temperature during this winter probably did not reach high enough temperatures to
cause any heat stress on the mussels.
This research provides a baseline for future work. Äfter a transplant that lasted
through winter and summer, the major growth period, the mussels could be measured
again. By the summer, any acclimation effect would likely be eliminated (Pickens 1965).
and any remaining differences between mussel populations might then reflect genetically
fixed differences. Non-genetic factors (e.g. gill size) that were initially set by
environment could then have lasting effects, unrelated to thermal acclimation. In
addition, the physiological tests could be repeated to show whether growth correlated
with respiration and MDH activity during a season of greater growth. Other indicators of
growth and physiology could also be used such as heart rate, calorimetry, and RNA:DNA
ratios. An enzyme that indicates only aerobic metabolism such as citrate synthase (CS)
might be more directly related to oxygen consumption than MDH. To research how
temperature changes affect growth, temperature could be directly manipulated in
laboratory experiments. The influence of age is another factor that should be examined.
By transplanting very young mussels, any age discrepancy would be reduced and
observed growth rates may be more reflective of actual population differences.
M. californianus is currently thought of as a genetically uniform species despite
its broad range in distribution. However, the field growth results of this research and
Sanford’s study suggest intrinsic differences between populations could exist. Further
research may suggest that M. californianus should be included in a growing body of
evidence that marine populations can vary substantially with latitude despite the lack of
obvious barriers to dispersal (Warner et al. 2000)
ACKNOWLEDGEMENTS
Thank you to George Somero, a fantastic advisor who was supportive of almost anything
1 wanted to try in the lab. Peter Field, where would I be without your help with the
biochemical assays and for letting me call you at home whenever I ran into a problem.
Thanks to Caren Braby who I asked a million questions and for helping me with all the
little things. The rest of the Somero lab thanks for helping me out whenever I got stuck
on something. I am most grateful to Eric Sanford without whom this project definitely
would not have happened. It’s a good thing you set up the whelk experiment in the field
otherwise, 1 couldn’t have done this project. Thank you for all the time you spent editing,
and re-editing, and re-editing and making my project what it is.
Thanks to my parents for all their encouragement to pursue research. Jonah, thanks for
everything.
LITERATURE CITED
Coe, W.R. and D.L. Fox. 1942. Biology of the California sea-mussel (Mytilus
californianus). I. Influence of temperature, food supply, sex and age on the rate of
growth. J. Exp. Zool. 90: 1-30.
Coe, W.R. and D.L. Fox. 1944. Biology of the California sea-mussel (Mytilus
californianus). III. Environmental conditions and rate of growth. Biol. Bull. 87:
59-72.
Dehnel, P. A. 1956. Growth rates in latitudinally and vertically separated populations of
Mytilus californianus. Biol. Bull. 110: 43-53.
Fox, D.L and W.R. Coe. 1943. Biology of the California sea-mussel (Mytilus
californianus). II. Nutrition, metabolism, growth and calcium deposition. J. Exp.
Zool. 93: 205-49.
Frandsen, K.T. and H.U. Rissgard. 1997. Size dependent respiration and growth of
jellyfish, Aurella aurita. Sarsia 82: 307-213.
Gosling E. 1992. Systematics and geographic distribution. pp.1-17 in E. Gosling, ed. The
Mussel Mytilus: Ecology, Physiology, Genetics and Culture. Elsevier Science
Publishers, Netherlands.
Hatcher, A., J. Grant, and B. Schofield. 1997. Seasonal changes in the metabolism of
cultured mussels Mytilus edulis L. from a Nova Scotian inlet: the effects of winter
ice cover and nutritive stress. J. Exp. Mar. Biol. Ecol. 217: 63-78.
Hochachka, P.N. and G.N. Somero. In press. Biochemical Adaptation: Mechanism and
Process in Physiological Evolution. Oxford University Press, Oxford.
Helmuth, B. 1999. Thermal biology of rocky intertidal mussels: Quantifying body
temperatures using climatological data. Ecology 80: 15-34.
Levinton and Suchanek. 1978. Geographic variation, niche breadth and geographic
differentiation at different geographic scales in the mussels Mytilus californianus
and M. edulis. Mar. Biol. 49: 363-375.
Morris, R.H., D.P. Abbott, and E.C. Haderlie. 1980. Intertidal Invertebrates of
California. Stanford University Press, Stanford, CA.
Paine, R. T. 1966. Food web complexity and species diversity. Amer. Nat. 100: 65-75.
Pickens, P.E. 1965. Heart rate of mussels as a function of latitude, intertidal height, and
acclimation temperature. Physiol. Zool. 38: 390-405.
Rao, K.P. 1953. Rate of water propulsion in Mytilus californianus as a function of
latitude. Biol. Bull. 104: 171-181.
Ricketts, E. F., J. Calvin, and J.W. Hedgpeth. Revised by D. H. Phillips. 1985. Between
Pacific Tides. Stanford University Press, Stanford, CA.
Schmidt-Nielsen, K.1997. Energy metabolism. Schmidt-Nielsen, K. Animal Physiology,
5“ ed. Cambridge University Press, Cambridge, UK.
Smaal, A.C., A.P.M.A. Vonck and M. Bakker. 1997. Seasonal variation in physiological
energetcis of Mytilus edulis and Cerastoderma edule of different size classes. J.
Mar. Biol. Ass. U.K.
Strathmann, M.F. 1987. Reproduction and Development of Marine Invertebrates of the
Northern Pacific Coast. University of Washington Press, Seattle.
Sukhotin, A.A.and H.O. Pörtner. 2001. Age-dependence of metabolism in mussels
Mytilus edulis (L.) from the White Sea. J. Exp. Mar. Biol. Ecol. 257:53-72.
Walsh, P.J. and G.N. Somero. 1981. Temperature adaptation in sea anemones:
Physiological and biochemical variability in geographically separate populations
of Metridium senile. Mar. Biol. 62: 25-34.
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Implications for the design of marine reserves and essential fish habitat. Bull.
Mar. Sci. 66: 821-830.
TABLES
Table 1a: Single factor ANÖVA test of respiration rates of gills between different treatment
groups.
Source of Variation
MS
P-value
Between Groups
6.95E-08
0.997487
0.413372
Within Groups
6.97E-08
Total
24
Table 1b: Single factor ANOVA test of MDH activity of gills between different treatment groups.
Source of Variation
P-valu
MS
Between Groups
0.000169
0.902587
0.291257
Within Groups
0.000579
Total
FIGURE LEGEND
Fig. 1. Diagram of the respiration chamber used in this study.
Fig. 2. Respiration rates of gills (n=6-7 per treatment) in the four treat groups. Error bars
are standard errors of the means.
Fig. 3. MDH activity levels of gills (n=10 per treatment). Error bars are standard errors of
the means.
ig. 4. Correlation of MDH activity and respiration.
Fig. 5. Correlation of dry and wet weights of gills.
Fig. 6. Photograph of Oregon and California gills.
Fig. 7. Winter growth of transplanted mussels (n-3 cages at Hopkins Marine Life Refuge,
n=6 cages at Soberanes Point). Error bars are standard errors of the means.
Fig. 8. High tide water temperature at Fogarty Creek, OR, Hopkins Marine Life Refuge,
CA, and Soberanes Point, CA prior to February transplantation.
Fig. 9. High tide water temperature at Fogarty Creek, OR, Hopkins Marine Life Refuge,
CA and Soberanes Point, CA prior to May collection of fresh mussels, and prior to
recollecting and sampling of transplants.
Fig. 1: Respiration Chamber
microelectrode
water
jacket
water
out

stir plate
gill mesh
package
—
perforated
platform
stir bar
water
in
22
0.0018
0.0016
0.0014
0.0012
0.001
0.0008
0.0006
0.0004
0.0002
u3o ou
Fig. 2: Mytilus californianus Respiration Rates
California
California Oregon
Oregon
Fresh
Fresh Acclimated Acclimated
Treatment
23
Fig. 3: Mytilus californianus MDH Activity
Oregon
Calitomia
Oregon
California
Fresh
Acclimated Acclimated
Fresh
Treatment
24
Fig. 4: MDH vs. Respiration
0.06
0.05

—
0.03
. * *
002
y =0.0004x +0.0232
0.01
R2=0.0754
000
0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00
MDH Activity (umol OAA/min/gram of tissue)
0.25
05
0.05
0
Fig. 5: Dry vs. Wet Weight Mytilus californianus Gills


.
y = 7.3888x + 0.0308
R2=0.729
0.015 0.02 0.025 0.03 0.035
0.005
0.01
Dry Weight (g)
26
Fig. 6: Variation in Mytilus californianus Gill Coloration
Lalise
Fig. 7 Winter Variation in Mytilus californianus Growth
MMussels from CA
HMussels from OR
Soberanes Point
Hopkins
Site
28
Fig. 8: Water Temperature (Dec '00-Feb '01)
13






V
Paa-

S
—Fogarty Creek, OR
-Hopkins Marine Life
Refuge, CA
— - Soberanes Point, CA
29
Fig. 9: Water Temperature (March ’01-May'01)
10




10



a
P

Date
—Fogarty Creek, OR
— Hopkins Marine Life
Refuge, CA
- Soberanes Point, CA
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