Introduction
Little is known of the effects of sewage on ma-
rine organisms. This study attempts to measure some of
the effects on the intertidal hermit crab Pagurus sam-
uelis (Stimpson, 1859).
Field studies were conducted at the sewer out-
fall on the southwest side of Point Pinos, Pacific
Grove, California. The city of Pacific Grove (pop.
14,000) dumps into the ocean approximately 14 million
gallons of primary-treated sewage per day. The outfall
is located about 0.5 feet above Mean Lower Low Water
in an area which receives heavy wave action. The sew-
age is composed mainly of suburban household wastes,
and contains almost no industrial or agricultural
wastes. Primary treatment removes grease, oil, and
other floatables, and allows some settlement of solids;
the treatment plant includes a digester which uses bac-
terial action to break down some organic material, obut
this was not operating effectively during the study
period.
Considerable controversy occurred in the fall
of 1969 concerning the quality of sewage treament by
Pacific Grove and other Monterey Bay communities. The
Monterey County Board of Health ordered the closing
of many beaches around Monterey Bay in September 1969
when counts showed coliform bacteria levels exceeding
those permitted in areas of water contact sports by the
State of California. "Cease and Desist" orders were is-
sued by the Regional Water Quality Control Board to
the city of Pacific Grove and other communities, and
later a ban was placed on further sewer connections.
Some time after the closing of the beaches, the Paci-
fic Grove sewage treatment plant stepped up its chlo-
rination in an effort to bring down coliform levels,
producing levels of residual chlorine up to at least
45 ppm and an extension of the visibly damaged area
around the outfall on Point Pinos by April 1970.
A preliminary survey showed hermit crabs to be
absent in the area. In subsequent studies, the distri-
bution of Pagurus genus was determined, the toxicity
of chlorinated and unchlorinated sewage to hermit crabs
was studied in both laboraory and field, and the ten-
dency of hermit crabs to move away from various con-
centrations of sewage in the laboratory was measured.
Outside of the distribution study, only P. samuelis
was used due to its more ready availability.
I. Intertidal distribution of Pagurus in relation to
the sewage outfall.
Anquantitative study of the distribution of Pa-
gurus was made in May,1970 at Point Pinos, and the
relative abundance of each of the four intertidal
1/6
species, P. samuelis, P. granosimanus, (Stimpson, 1859),
P. hemphillii (Benedict, 1892), and P. hirsutiusculus
(Dana, 1851), was determined.
Twenty-eight one meter wide transects were ex-
amined at low tide at various locations on Point Pinos.
Each transect was approximately 10 meters long, begin-
ning at the low water level of the ocean at the time
-1.0 to 0.0 feet in tidal height). Every hermit crab
as it was found was scored as to (1) species, and (2)
approximate size, using the width of the base of the
shell (always of the turban snail Tegula in adults) as
a rough measure of the size of the individual. Adults
were identified using Light's manual (Light, Smith,
Pitelka, Abbott, and Weesner 1964), and juveniles using
Putnam and Markham's key (Putnam and Markham, 1965).
Populations in three large tidepools were considered
as separate units. For each transect or large pool, the
following were determined: (a) the total number of Pa-
gurus, (b) the total number of each species, and (c)
the total number in each size-class for each species.
Three size-classes were defined: large (shell base
width greater than or equal to 20 mm; carapace width
greater than 7.5 mm); medium (shell base width 10 to
19 mm; carapace width 2.5 to 7.5 mm); and small (shell
base width less than 10 mm; carapace width less than
2.5 mm).
Areas with suitable Pagurus habitat (pools
which do not drain even at lowest tides) were deli-
neated. Relative abundance of Pagurus in each area
was scored as follows (see Fig. 1): abundant (over 100
individuals per transect or 10 m2); fairly common (20-
99 per transect or 10m2); scarce (less than 20 per
transect or 10-m2); absent (no individuals eseened)
Areas where no transects were taken were examined qua-
litatively.
Location of transects and totals for each species
and size class for the transects are given in Appendix
A; areas containing suitable habitat and the relative
abundance of the genus in each area is given in Fig. 1.
No alterations in the pattern of distribution were ob-
served where the genus was present: in areas below
+1.0 feet in tidal height, large P. granosimanus and
small P. hirsutiusculus were by far the most common,
and above t1.0 feet, P. samuelis was the only species
found, with all three size classes being common. The
general distribution of the genus in relation to tidal
height and the relative abundance of the size classes
conformed to that found by Belknap and Markham (1965).
In only two areas was Pagurus abundant, and in
most areas the genus was classified as scarce. Pagurus
was absent within about a 100 foot radius of the out
fall, although the abundance of pools within this area
would normally make it highly suitable for Pagurus. Al.
gal coveri is greatly reduced or lacking within this
100 foot radius. Pagurus was also absent in two areas
of Cove A. Areas where hermit crabs were abundant or
fairly common were as close to the outfall as 120 feet,
just outside the area where they were absent.
The heterogeneity of the intertidal makes it
difficult to say much more about the distribution of
Pagurus at Point Pinos than that they were absent
within a 100 foot radius from the outfall, and that Pa-
gurus isgenerally not very common at Point Pinos. In
no area was the density of Pagurus as high as that found
at Mussel Point approximately two miles southeast of
Point Pinos.
II. Field studies on the toxicity of sewage to Pa-
gurus samuelis
The toxicity of sewage under field conditions
over a one month period was determined by placing wire
cages containing P. samuelis at different distances
from the outfall (Fig. 1). A control was placed at the
Hopkins Marine Station on Mussel Point, a locality con-
sidered to be unpolluted.
Cages were constructed of stiff, 4 in, mesh, galvan-
ized wire screen molded into flattened cylinders about
60 cm long, 15 cm wide, and 10 cm high. Twenty-five P.
samuelis collected at Mussel Point were placed in each
cage: 6 large, 14 medium, and 5 small. The small ones
were placed inside a separate envelope of plastic
screening 12 cm by 5 cm. Rocks were added to the cage
for weight. A dead gooseneck barnacle (Pollicipes po-
lymerus) was added to each cage for food at weekly in-
tervals, although Richardson (1965) found these crabs
can live for 30 days without food with only 7.6% mor-
tality. The density if the animals in the cages was
roughly half that calculated by Richardson (1965) to
give less than 20% mortality in 5 days. On 1 May 1970
11 cages were placed at Pt. Pinos in pools where they
were always submerged. All were below a tidal height
of 0.0 feet except cage 4. The cages were wedged un-
der or between rocks in the pools and were not moved
by wave action.
Cages were examined every other day when tides
permitted; the longest period between successive ob-
servations was 7 days, but this came after the period
when most mortality occurred. The number of dead indi-
viduals in each cage was recorded at each observation.
An individual was considered dead if (a) an empty
shell but no body was found, or (b) the animal showed
no resistance to being removed from its shell and
showed no response to prodding after 10 minutes in
fresh sea water.
The percentage of surviving animals at each ob-
servation is given in Fig. 3. and the time at which
50% mortality (Lethal Time 50) occurred in relation
to distance from the outfall is given in Fig. 2. All
animals died within 9 days in cages within a 100 foot
radius of the outfall, death occurring most rapidly in
cages closest to the outfall. Mortality in cage 6, 110
feet from the outfall, reached 72% in the 28 day ob-
servation period. The remaining cages, including the
control, showed 8 - 16 % mortality in 28 days, which
is approximately the same as in controls maintained in
the laboratory (see below). Cage 11 was destroyed by
children.
A very short LT 50 was found in cage 4, despite
its relatively great distance from the outfall. It was
12
situated in a high tidepool (13 feet in tidal height)
rather than below 0.0; polluted water is thus trapped
here for longer periods of time than at lower levels.
The field cage study shows that any P. samuelis
within a 100 foot radius of the outfall were killed
but beyond 110 feet there were no lethal effects in
four weeks. This correlates with the distribution
study, which showed no P. samuelis within the 100 foot
radius. A high mortality did occur in cage 6, where
large numbers of living P. granosimanus and P. hirsu-
tiusculus were found; however, the living crabs were
concentrated at the end of the pool farthest from the
outfall, and the cage was at the nearest end, where few
living Pagurus were found. Field observations show that
murky water from the outfall begins to seep into the
pool as the tide rises to about 1.0 ft. in tidal height;
thereafter it is flushed out with clean water from the
opposite direction as the tide reaches about 13.0 ft.,
and heavily polluted water is not concentrated in the
far half of the pool.
In a similar field cage study conducted by the
author in August 1969, no significant mortality occurred
in any cages within the 100 foot radius in 12 days. The
closest cage to the outfall was 15 feet away. This was
before heavy chlorination, thus implicating chlorine
as the factor producing high mortality in May 1970.
III. Laboratory studies on the toxicity of sewage to
Pagurus samuelis.
Experiments to determine the short-term tox-
icity of sewage to P. samuelis in the laboratory were
carried out as follows:
In each test 25 P. samuelis (5 large, 10 medium,
and 10 small) were placed in shallow plastic dishes
each with a bottom area of about 600 cm2. This is the
approximate density calculated by Richardson (1965) to
give less than 20% mortality in 5 days (25 aniamls per
525 cm), although only 8% mortality in 29 days occurred
in controls in this experiment. Occasionally larger
dishes with a bottom area of 1000 cm were used, and
the number of individuals in these dishes was raised
to 40 to acheive the same density. The animals never
utilized all the area available to them, clustering
in the corners most of the time; thus crowding was not
thought to be a critical factor. Each group of animals
was given a 24 hour acclimation period in fresh sea
water before antest, since Richardson (1965) states
that most mortality-producing interactions occur in
the first four hours. In 25 experiments, however, only
2 out of 705 hermit crabs were found dead after the ac-
climation period.
16
10
Fifteen-hundred ml of solution were added to
the smaller dishes and 2000 ml to the larger ones, gi-
ving a depth of about 1.5 inches, in which the animals
were continuously submerged. No aeration other than
diffusion was used since the surface to volume ratio
was large. Dishes were placed in a circulating sea
water bath to maintain a constant temperature of about
14°. This is slightly higher than the average sea
water temperature during May in Monterey Bay (12°0),
but is well within the temperature ranges if the high
tidepools in which P. samuelis abounds, and is well
below thermal death point for P. samuelis (31.500;
Forward, 1965).
The following solutions were tested:
(a) chlorinated Pacific Grove sewage at con-
centrations of 100%,50%,20%,10%, and 1%. Chlorine
levels in straight sewage ranged from 15 to 45 ppm
as determined by idiometric titration as given in
Standard Methods for the Examination of Waste and
Wastewater,1966. Residual chlorine levels were found
to drop by about 25% after 6 hours after arrival from
the sewage plant. No chlorine was ever detected in the
1% concentration, but the assay was not sensitive in
the levelseexpected at that concentration.
(b) Pacific Grove sewage at concentrations of
100%, 50%, 20%, 10%, and 1%, but dechlorinated with
11
sodium thiosulfate, Na2S203, to determine if chlorine
was a toxic factor; 0.36 g of thiosulfate were added
for each liter of sewageiin the solution. Thisiwas
enough to neutralize approximately 100 ppm chlorine,
more than twice the amount ever detected in the sewage.
(c) a control for (b) alone using sea water and
sodium thiosulfate at 0.36 g/liter, the highest concen-
tration in any solution, to determine if thiosulfate
itself could be toxic.
(d) 100% Pacific Grove sewage dechlorinated
with O.36 g/liter thiosulfate and raised to the salin-
ity of sea water by adding 33.5 grams of "Instant
Ocean" salts per liter of sewage.
(e) unchlorinated sewage from the treatment
plant of the adjacent city of Monterey in concentrations
of 100%,50%,20%,10%, and 1% to compare the relative
toxicities of sewage from the two areas.
(f) distilled water at concentrations of 100%,
50%,20%,10%, and 1% for an osmotic control.
(g) tap water at 100% concentration. Tap water
is closer to the salinity ofsewage than distilled water.
(h) 100% sea water control.
Two tests instead of one were meade for each 100g
solution showing toxicity (50 animals). The larger
dishes (40 animals) were used for all 50% concentrations.
All dilutions were made using sea water from
2
12
the sea water system at Hopkins Marine Station. One
or two gooseneck barnacles (Pollicipes polymerus) were
fed to each group once a week. Uneaten portions were
removed after 18 hours to prevent fouling of the water.
As mentioned above, food was not considered a critical
factor in mortality (Richardson, 1965). Fresh sewage was
obtained every morning from the Pacific Grove, and
Monterey sewage plants, and test solutions were
changed within 2 hours thereafter. Solutions not con-
taining sewage were also changed daily.
Each test solution was examined at intervals
determined by the relative toxicities of the solutions,
i.e. hourly if highly toxic or twice daily if no rapid
mortality observed. Criteria of death were as follows.
Individuals showing no response to prodding were re-
moved and placed in fresh sea water; if after 15 mi-
nutes there was no response to prodding and if the
mouth parts were not moving, the individual was con-
sidered dead. Often individuals showing no response in
the test solution showed limited movement of appendages
within 5 minutes exposure to fresh sea water; but twice
about 10 animals scored as dead were left for twelve
hours in fresh sea water without recovering.
The percentages of surviving animals versus
time for 100% and 50% solutions appears in Figs 5 & 6.
The LT 50's for chlorinated Pacific Grove sewage are
6
given in Fig. 4 (compare with mortality in field cages,
Fig. 3). The only solutions below 50% concentration
showing mortality significantly greater than the con-
trol (8% in 29 days) were 20% and 10% Pacific Grove
chlorinated sewage. The duplicate runs in 100% concen-
trations showed virtually identical rates of death. All
three size classes showed very similar mortality rates
in toxic solutions.
Appendages of individuals killed in high con-
centrations (100%,50%,20%) of chlorinated sewage were
constricted, whereas in 10% chlorinated sewage and all
other types of toxic solutions, the appendages at death
were relaxed. When high mortality occurred in solutions
with LT 50's greater than 100 hours, the bristles on
the appendages were whitened, extended, and prominent,
with much adhering particulate material. Death in so-
lutions with mortality in the range of the control ap
parently resulted from predation, although the actual
act was never observed; a half-eaten body, a few appen-
dages, or an empty shell provided evidence of the
cause of death here. Never was a crab found just sit-
ting dead in its shell in non-toxic solutions, and
very seldom were half-eaten crabs found in toxic so-
lutions. No interest in food was shown in solutions
with LT 50's under 30 hours.
From the laboratory studies it can be seen that
chlorine is the most toxic component of sewage, since
27
chlorinated sewage was the only solution tested which
caused significant mortality in concentrations below
50%. When chlorine was neutralized with thiosulfate,
no significant mortality occurred in concentrations
below 50%.
Fresh water also contributes to the toxicity
of sewage, for when dechlorinated Pacific Grove sewage
was raised to the salinity of sea water, its LT 50 in
creased from 13 hours to 27. Also, significant mortal-
ity occurred in 100% and 50% distilled water and 100%
tap water (see Figs. 5 & 6). Unfortunately tap water
concentrations below 100% were not tested, but the
LT 50 for pure tap water (18 hrs.) was significantly
higher than that for pure distilled water (10 hrs.),
which has a lower salt content.
While both chlorine and fresh water are toxic
components of sewage, there are still other toxic
factors, since when the chlorine was removed and the
salinity raised, mortality still occurred, although
at a lower rate. Also, distilled water proved much
less toxic at 50% concentration than the same concen-
tration of dechlorinated sewage.
Since in laboratory experiments sewage solutions
were changed once a day, the situation here differs
somewhat from that in the field: near the outfall at
high tides fresh sewage is added continuously to the
12
area, and only at lower tides would an animal be ex-
posed for prolonged periods to the same sewage solution.
No studies were made of the changes occurring in sew-
age with time other than to note the decrease in chlo-
rine content. In any event, since the composition of
effluent at the outfall probably varies widely depen-
ding on the time of day, it would be difficult to si-
mulate in the laboratory the exact conditions which
animals encounter in the field. Another factor to be
considered is that some areas in the field may receive
concentrated doses of sewage for only short periods of
time, and the effect of this was not tested in the
laboratory.
From the laboratory studies it can be seen that
the rapid mortality rate noted in field cages placed
around the outfall is probably due to chlorine, since
the concentration of sewage without chlorine necessary
to produce the LT 50 found at 60 feet would have to be
greater than 50% (see Figs. 3 & 4). The LT 50 at 60
feet from the outfall (96 hrs.) more closely corre-
sponds with that for 10% chlorinated Pacific Grove
sewage (91 hours) than that of 50% dechlorinated Pac-
ific Grove sewage (212 hrs.). Most components of the
sewage were found to be diluted to 20% or less at 60
feet (Hopkins Marine Station chemical study group,
pers. comm.), and thus mortalities at this distance
are more likely caused by a 10% concentration than a
50% concentration. As much as 6.9 ppm residual chlorine
was detected 60 feet from the outfall on some days, al-
though none was found on others (Elaine Anselmo, pers.
comm.); this is about 20% of the average chlorine con-
tent of the effluent.
17
IV. Movement of P. samuelis away from sewage
It was hypothesized that the absence of P. sa-
muelis in the outfall area might be accounted for by
movement of the animals away from the outfall, and so
an experiment was devised to measure movement out of
various concentrations of sewage.
Plastic boxes l0cm by 10 cm and 6 cm deep were
clamped togehter in pairs joined by a strip of plastic
screening extending from the floor of one box to the
floor of the other. The hermit crabs could thus easily
climb out of one dish and into the other, using the
screen as ladder and bridge. The boxes were filled with
test solutions to within 5 mm of the top (about 500 ml).
Each pair of boxes contained sea water in one and test
solution in the other. Controls were run with sea water
in both boxes. The sewage was brought to sea water
temperature before use (from about 18°c to 14°c).
During the experiments the solutions warmed gradually
to about 16°0. No aeration was used.
The following solutions were tested, each at
100%,50%,20%,10%,and 1% concentrations: (1) unchlori-
nated Pacific Grove sewage, (2) unchlorinated Pacific
Grove sewage raised to sea water salinity by adding
33.5 g "Instant Ocean" salts per liter sewage, and
(3) tap water for an osmotic control.
18
Five large or medium P. samuelis collected in
unpolluted pools at Hopkins Marine Station were placed
in every box at the start of each experiment, and their
positions recorded after one hour. Ten trials were run
with each dilution of each solution, to give 100 in-
dividuals for each test. New crabs were used in each-
trial.
Almost as soon as crabs were placed in the con-
tainers, rapid movement occurred between the two solu-
tions. Only 5% of the animals tested never left their
original boxes. The plastic screen bridge was easily
climbed, but a substantial percentage of animals pre-
ferred to remain on the bridge rather than stay in
either solution. Most movement ceased in 45 minutes.
The percent of individuals in each box and on the
bridge after one hour is given in Table 1. What was
considered important was the ratio of the number of
individuals in the sea water box to those in the test
solution box; this is given for each test in Table 1
and plotted against concentration of solution in Fig. 7.
The experiment did not work with higher con-
centrations of chlorinated Pacific Grove sewage, since
most animals were incapable of climbing the bridge af-
ter 5 minutes in 100%,50%, and 20% concentrations.
Only one of 30 animals tested remained in 10% Pacific
Grove chlorinated sewage after one hour, but no pre-
ference was shown between 1% Pacific Grove chlorinated
sewage and sea water.
In the movement experiments, a solution was con-
sidered to produce movement away from it if the ratio
of individuals in the sea water box to those in the
test solution after one hour was greater than 2:1. The
three controls averaged 1.2 : 1, fairly close to the
l:l ratio expected by chance alone. On this criterion,
movement shown seems to be related mainly to reduc-
tion in salinity; sewage and tap water dilutions
showed approximately the same ratios, but sewage so-
lutions adjusted to sea water salinity by addition of
sea salts produced no movement except in 100% concen-
tration. Movement away from 100%, 50%, and 20% so-
lutions of both sewage and tap water was recorded,
but not at 10% and 1% concentrations. If movement away
from an area is responsible for the absence of P. sa-
muelis there, the experiments suggest the animals move
cif the salinity is at or below 2700/00, but nothif higher
than about 30 0/00. Since salinities measured were
lowerröthan 30 0/00 in the field only within a 25 foot
radius of the outfall, it seems likely that the absence
of P. samuelis within a 100 foot radius is not due
solely to movement away from the pipe.
Summary
1. Pagurus is absent within a 100 foot radius of the
Pacific Grove sewage outfall. No abnormalities in
the patterns of distribution of Pagurus were found
outside the 100 foot radius.
2. Field cages containing P. samuelis placed within a
100 foot radius of the outfall showed 100% mor
tality in 28 days. Beyond this distance, mortalities
did not exceed those in unpolluted areas.
3. Chlorinated sewage (residual chlorine 15 - 45 ppm)
was the only one of several solutions tested in the
laboratory (including dechlorinated sewage) showing
significant mortality in 20% and 10% concentrations.
Chlorine was probably the cause of deaths recorded
in field cages within 100 feet of the outfall; lab-
oratory studies showed sewage without chlorine could
not account for this mortality except in concentra-
above 50%.
4. Fresh water is a component of sewage toxic to P. sa-
muelis at salinities of 0 - 17 0/00, but not toxic
at 27 0/00 and above in115 days.
5. Other toxic components are present in sewage since
mortality exceeding that of controls was recorded in
sewage which was dechlorinated and osmotically bal-
anced.
1
6. P. samuelis tends to move away from solutions with
salinities at 27 0/00 or below, but this alone pro-
bably cannot explain the absence of this species
within the 100 foot radius of the outfall.
P. samuelis is not a sensitive indicator for un-
chlorinated sewage, but is very sensitive to chlor-
inated sewage. If sewage is not chlorinated, P. sa-
muelis could survive for prolonged periods in 20%
concentration of sewage
22
Acknowledgments
These investigations were supported in part
by the National Science Foundation Undergraduate Re-
search Program, Grant no. GY-7288. I wish to thank Dr.
Donald P. Abbott for his help and suggetsions during
the experiments and his invaluable criticism of the
manuscript. I would like to thank James Schreiber for
making his chlorine testing apparatus available to me.
Elaine Anselmo provided chlorine data from the outfall
area, and Victor Anderlini, Elaine Anselmo, Dave Clear-
man, John Hainsworth, Marshall Holstrom, and Tom Rot-
kis cooperated with me in obtaining chemical data at
Point Pinos. Marshall Holstrom provided the Pollicipes
used for food.
23
References
1966. Standard Methods for the Analysis of
Waste and Waste Water. Am. Public Health
Assoc. New York. pp 376 - 378.
Pers, comm: unpublished data from Point
Pinos chemical study group. May 1970.
Elaine. Pers, comm: chlorine levels at
Anselmo,
Point Pinos. May 1970.
Robert and John Markham. The intertidal
Belknap,
and subtidal distribution of four species
of Pagurus (Fabricius) at Mussel Point,
California. Unpublished student report,
1965. Hopkins Marine Station, Stanford
University. pp. 20 - 43.
Richard. 1965. Effects of temperature and
Forward
dessication on Pagurus samuelis and Pagurus
granosimanus at Pacific Grove, California.
Unpublished student reports, Hopkins Marine
Station, Stanford University. pp.126 - 150.
Light, S.F., Ralph I. Smith, Frank A. Pitelka,
Donald P. Abbott, and Francis M. Weesner.
Intertidal Invertebrates of the Central
California Coast. Berkeley, 1964. pp. 183,
244, 245.
John D. and John C. Markham. 1965. Charac.
Putnam,
teristics of larval and postlarval stages
for Pagurus in Monterey Bay, California.
Unpublished student reports, Hopkins Marine
Station, Stanford University. pp 198 - 217.
Richardson, Norman. 1965, Some factors of mortality
in laboratory populations of Pagurus samuelis.
Unpublished student reports, Hopkins Marine
Station, Stanford University. pp 218 - 230.
Figure 1
Distribution of Pagurus at Point Pinos
and location of field cages. Numbers indi-
cate position of field cages. Areas deli-
neated contain suitable Pagurus habitat.
2-
outfall
COVE A


12 at-HOPKINS MARINE


o

0
a
E
Figure 2
Relation of LT 50 to increasing dis-
tance from outfall for field cages. Numbers
refer to specific field cages given in Fig. I.
Dashed line indicates distance beyond which
no significant mortality ogcurred. Cage 4
was in a pool 3 feet higher than the other
cages.
9.
SAOOH
0g



O
LL
L
LE
Z
Figure 3
Per cent survivors as a function of
time for animals in field cages at Point
Pinos. Numbers refer to specific field cages
as given in Fig. 1. Cage 4 was in a pool
3 feet higher in tidal height than the other
cages.
9.


0


O
SAOAIAAOSINd
8
V.
Figure 1
Per cent survivors as a function of time
for Pagurus samuelis exposed to chlorinated
Pacific Grove sewage.
Letters indicate concentration:
A - 100%
B
50%
C -
208
10%
18
F- sea water control
1
SAOAIAAOS
INSD


Aad

1
1
Figure
Per cent survivors as a function of
time for Pagurus samuelis exposed to 100%
solutions.
Letters indicate type of solution:
chlorinated Pacific Grove sewage
b-
distilled water
unchlorinated Monterey sewage
dechlorinated Pacific Grove sewage
tap water
dechlorinated and osmotically ba-
lanced Pacific Grove sewage.
g - sea water
9.
2

SAOAIAAOS INA
a


18
Figure
Per cent survivors as a function of
time for Pagurus samuelis exposed to 50%
concentrations of test solutions.
Letters indicate type of solution:
a - chlorinated Pacific Grove sewage
distilled water
unchlorinated Monterey sewage
dechlorinated Pacific Grove sewage
pure sea water control
*
00

1
SAOAIAAOSIND ad
Table 1
Movement of P. samuelis away from sew-
age: Per cent individuals in each box after
one hour. All boxes began with 5 in sea water,
0 on bridge, and 5 in test solution, and 10
runs were done for each concentration.
A - unchlorinated Pacific Grove sewage
B - unchlorinated and osmotically ba-
lanced Pacific Grove sewage.
C - tap water.
A
B
C
Concentration
ofsewage
1008
507
204
10
19
sea water
control
Concentration
ofsewage
100%
505
204
0%
sealwater
control
Concentration
water
of tar
100%
504
258
163
12
seanwater
control
sea
water
29
sea
water
12
sea
water
67
58
55
38
bridge
bridge
28
32
bridge
28
29
sewage
44
sewage
127
120
39
27
tap
water
16
142
116
Tatio
S.Wse
112
ratio
s.w./sew.
918
2
ratio
s.W./tap
13.4
3.4
Toble
15
Figure 7
Movement of P. samuelis away from sew-
age : per cent concentration of test solution
ys. ratio of individuals in sea water box to
individuals in test box.
A - unchlorinated Pacific Grove sewage
B - unchlorinated and osmotically ba-
lanced Pacific Grove sewage.
C - tap water
95

u


uoljojos
1891 10
ouu ue5 le

8
—

.2
9
Appendix A
Location of transects for Pagurus di-
stribution study at Point Pinos.
S
OUTFALL

50 100
feet
—
V

—
POOL
Pool A
01716
1514
o
W
22
24
26

28.
25

20
21


a
06
U
Aepend
/88
Appendix E
Numbers of Pagurus found on each tran-
sect in distribution study at Point Pinos.
Numbers refer to transect number in Appendix
A, and letters refer to pools in Appendix A.
4

L L

Z T
« -
ap; 2
10
11
12
14
15
17
18
19
20
21
22
23
24
25
26
27
28
B
2 0
—
12
T a
0
13
7
40
27

a
29
0
—
28
20
21
39
48
57
ao
11
15
12
11
12
25
17


4
OIAIO
TaodLaa
0
22
48
682
188