This is a student paper done for a University of California Berkeley Zoology class. Since UCB didn't have its own marine lab at the time, it rented space at Hopkins Marine Station where this work was done. Cadet Hand earned his Ph.D. from Berkeley and went on to become Director of the Bodega Marine Laboratory.  Donald Putnam Abbott also earned his Ph.D. from Berkeley and later became a Stanford professor at Hopkins Marine Station.  (PDF contains 26 pages

Abbott, Donald P.

Davis, John

Hand, Cadet

English

Aquatic Commons

THE DISTRIBUTION OF CIRRIPEDS AND GASTBOPODS ON PLAIN VERTI- ft 
CAL BOCK SURFACES IN THE UPPER INTERTIDAL AND SPLASH ZONES. 
1 ' DR. S. 1'. LIGHT I - 
PROPERTY OF DEPT. OF ZOOLOGY 
"MV. OF CALiF., BEKKELEY 
* 
CADET HAND 
DONALD P. ABBOTT 
JOHN DAVIS 
I 
ZOOLOGY S212 
Hopkina Marine Stabion 
July 28, 1947. 
Introduction.
The problem consisted of two phases, firstly, a quallta~1.ec
determination of the distribution of the species of barnacles and
gastropods present from the top of Zone 1 (of Ricketts and Calvin)
to about the top of the ~ytilu8 line (or its equivalent height) on
"
vertical rock surfaces, with special emphasis on the space relation-
ships of anyone species to the other species encountered, and se~
condly, the obtaining of a quantitative measure of the effects of
exposure to various degrees of wave action and splash on the pattern
of vertical distribution of the above species.
All counts were made on Mussel Point duriD8 the period July
'-July 14, 1947.
Methods.
Selection ~ sites.
Ideally, the sites chosen for such a study should have been
identical in all respects save in the two variables under conside-
ration, i. e. , degree of exposure, and distribution of organisms.
In practice, sites were chosen Which presented one or more verti-
cal faces of rock extending throughout the major part of the area
under consideration, which had relatively homogeneous surfaces, as
free as possible of projections, crevices, ledges, caVities, and
other modifying factors creating local areas at variance with the
general area type here considered, which showed obvious differen-
ces in degree of exposure to wave action and 'splash, and which were
readily available for study.
Five s1.tes on :-4ussel Point, Pacific Grove, Calif., were cho-
sen, one of Which (Point Despair) was later abandoned as unsuitable.
'r The other four, although not ideal, were acceptable for stUdy. In
order, from the most exposed to the least exposed, these were: High
Rock, Hot Rock, . .il4urphy' s Rock, and Snad Rook. The locations and
descriptions of these sites are inoluded under the section on Re-
sults.
Laying~ ~ transects.
A vertical strip, 6 tt wide, was lltaid out with red 'Wax pencil
and steel tape on each rook from top to bottom, and subdivided into
6" by 6" squares. Intervening orevioes which contained an assort-
ment of organisms quantitatively and qualitatively atypical of the
surrounding vertioal exposed surfaoe were ignored, although they
contained gastropods which might migrate out over the exposed sur-
face from time to time. It is felt that this disregard for crevice
fauna did not significantly alter the results.
In areas where one exposed rook did not extend to the mussel
line or its equivalent (as in all except Murphy's Rook), the tran-
sect was interrupted, and oontinued at the next suocessive level on
the olosest similar and suitable rook faoe. This had a notioeable
effect on the counts in at least two cases (High Rock and Snad Rock)
but could not be avoided..
Matins oounts.
Counts were made by removing with knives all organisms from
the rook within one 6 11 by 6" square, in the following order: litto-
rines, limpets, and barnacles. All organisms within the square and
"on the line" were counted as they were removed. Hence all identi-
fications were made in the field except in the case of a few trou-
blesome limpets, subsequently graciously identified by a local au·
thority, Miss B. Sohuok.
Certain sources of error were inevitable, due to the hetero-
geneous nature of the terrain, the enormous numbers of organisms
present in the lower squares of the transects, and the methods used
I~
-3-
for removal of individuals as they were counted. Many small litto·
rines, particularly those living inside the shells of dead barnacles,
were undoubtedly overlooked. In areas encrusted with mixed barnacle
populations, it was almost imposmble to remove and count the indi-
viduals of one species without disturbing adjacent individuals of
the other species. In gemral, it is felt that the margin of error
in counts. of L. R.!Lnaxis and of the various speoies of Acmaea was
negligible, ani d1 d not exceed 5% for the other species counted.
Altho~ no control transeots were oounted, ,qualitative vi-
sual observation of areas adjacent to the transects indicated a va-
riat ion pres ent on t he tot al surf so e of any rock at any particular
time, such varlat ion constituting another uncontrolled variable.
Results.
Descriptions ~ figures ~ sites studied.
~ Rook. (See Figs land 2). This rock, located on·the NNW
face of Mussel Polnt, Is exposed to a relatively high degree of wave
action as compared With the other localities chosen. The rock it-
self extends from about 15 teet to about 3 feet above the mussel
line, in the region of t he transect studied. The 6 lower squares
counted that were not on High Rock itself were located on the near-
est flat vertical surfaces, only a few feet away. The outer sur-
faoe of High Rock is marred by a transverse crevice near the top,
and by another about one third of the way up. The transect was bro-
ken at these points to exclUde the orevices.
The outline of the rock 1s not vertical. The angles of the
var10us surfaces measured may be estimated from Fig. 2.
A sharp break in the continuity ot numbers of organisms coun-
ted 1s mown in the counts for High Rock between squares 33 and 34,
and between squar as 34 and 35 (Fig. 2), indicating that conditions
-4-
in the three regions were not strictly comparable. Observations
made at high tide show that squares 34 and 35-39 receive much grea-
ter splash and wave pounding than square 33 and the squares above it.
Waves strike the base of the rock at a s11ght angle, but not
,
enough to prevent considerable splash at h1gn t1de.
~~. (See Figs 3 and 4). Hot Rock is situated on the west
face of Mussel Point. It 1s SUbjected to a fa1rly high degree of wave
action, since the direction of the incoming waves is on a line with
the vertical surface of the rock. However, compari8ion of Figs 1 and
2 with Figs 3 and 4 will show that the vertical aspect of Hot Rock
is protected by extensive mussel-covered reefs which mitigate the
shocking power of the impinging surf. Reference to Fig. 4 wUl clear-
ly show the two discontinuities in the transect. However, neither or
these breaks had aDl marked effect on the counts, since the upper-
most occurs high in the splash zone, and the lower is small.
The transect studied extends 11 feet, from the top of the
outer face ot the rock to the mussel line.
Murphy's Rock. (See Figs 5 and 6). Murphy's Rock is situated
on the south face of Mussel Polnt, lying in an open cove protected
to the north by a prominent rocky spit. Incoming waves pass across
the face of the rock parallel to its surface, and consequently the
splash zone is limited. In outline, the outer face of the rook is
nearly vertical, and is unbroken by any fissures or ledges. This is
in marked contrast to the other rocks studied.
§nag Rook. (See Figs 7 and 8). Snad Rock 11es on the north
face of Mussel Point. Although the incoming waves impinge direct~
on the rock, their force is abated by a perfectly overlapping series
at protecting rooks. The result is that incoming water merely swells
-5-
,
about the baae of the rock with very little force, reducing the
splash zone to a minimum. The transeot on Snad Rock is interrupted
by one major discontinuity, as illustrated in Fig. 8; this produced
a corresponding discontinuity in the number ot organisms present in
..
squares 9 and. 11. Since squares 9 and 10 (see Fig. 8) were at the
same level, the oounts in squaN 10 were not included 1n the charts
(see Appendix, Table 4, footnote).
Check-list .Qt speci..!! tound.
The following organisms were found in the transects studied:
Class Clrripedia.
Order Thoracica.
Balanus Mandula: Darw1n
Chthamalus !J:!§Y.! Darwin
Tetracl1ta squamosa rubescens Darwin
Class Gastropoda
Order Streptoneura
Suborder Aspidobranchiata
Acmaea digitali~ Eschscholtz
Acmaea pelta Eschacholtz
Acmae~ digitalis x Acmaea pelta
Acmae.! 8cabm (Gould)
Suborde r Pectinibranchiata
Littoripa planaxis Philippi
Littorina scutulata Gould
Class Pelecypoda
Order Filibranchlata
Mytl1y! g!ll9rnlanus Conrad
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Basic pattern of distribution ot organisms.
According to Hewattl the organisms .studied occur in the inter-
tidal zone as follows:
+7' ~G' ...5'
.Ir
In the course of the present study, no such clear cut basic
plan of distribution as the above was found which was applicable to
all rocks. It is possible. however. to point out certain basic trends
that were noted. Littorlna planaxls always ranged higher than any of
the other organisms. In general, the highest ACffiaeas occurred slight-
ly higher than the highest barnaclesv While Acmaea digital1s 1s ge-
.
nerally believed to range slightly higher than A. scabra in the
rocky intertidal, our coun~s and qualitative observations did not
consistently bear this out. and it appeared that the height reached
by the highest individuals of the two specie~.~as about the same.
Slightly below the highest limpets, the outposts of the barnacle
frontier appear. and again, neither B. glandula or c. tissus -
I~
within the areas counted • could be said to occur oonsistently high-
er than the other as far as isolated individuals were ooncerned.
1 )
Hewatt, W. G. 1937. Eoological studies on selected marine intertidal
communities ot ~onterey Bay, California. Am. Midland Nat., 18: 161-
206.
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-7'--
The most variable species in the array studied was Littorina
scutulata. Even disregarding all specimens which had worked their
way into noticeably protected areas, and considering only those
freely exposed on bare rock faces, the highest L._ scutulata might
appear anywhere from above the highest .u.impets to below the highest
barnacles •
. Only in the cae e of L. Qlanaxis did the areas counted inelude
the lower limit of distribution in the intertidal, eo that a com-
plete distribution picture f~r the other species i~ lacking. A fur-
ther understanding of the distribution of the species concerned must
await counts extending farther downward, and studies as well of the
microhabitats of exposed rocky surfaces, and of the movements made
by the limpets and littorines.
Charts.
See following page.
-8-
D.iscussion.
The results obtained are shown in the foregoing charts and. in
the tabulations or actual organisms counted (see Appendix) with suf-
ficient clarity to render extended discussion superf'luous. The gene-
rally higher ranging of forms in region' of greater wave action and
splash is obvious) as is the variatio.n in degree' of t(compression"
. ..
of the vertical distribution belts of the organisms studied, such
variation being direct~ correlated with the degree of protection
from splash. Oertain features, howeven; require e~has1s ,·and/or ex-
planation.
In the first place, conclusions concerning the large numbers
of organisms found in the lowermost regions counted (especially in
the case of Murphy's Rock) must be made with caution, as correspon-
ding low areas were not counted on all rocks. Secondly, certain pecu-
liar features of Snad Rock make it difficult to compare directly
with the other regions. It receives almost no spray at all, the waves
at low tide scarcely rising above the water level. Hence, barnacles
are forced to live in a region covered by high tides. However, here
they must compete for attachment sites with the algae, Which grow up
nearly to th~ high tide mark. The r~sult~ situation has apparently
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crowded the barnacle belt nearly out of existence. This may not pre-
sent the whole picture, as horizontal rocks adJ acent to the lower
squares on Snad Rock are almost completely encrusted with barnacles. ~
In some instances, the presence of cert~ln organisms made possi- I
ble the presence of others. This was particularly true in the case of
small specimens or 1. scutulata, since many tiny individuals occurred
inside the shells or dead barnacles, and in the crevices between ad-
Jacent barnacles.
Finally, the degree of exposure was not measured quantitative-
ly. However, qualitative observations at high tide afforded a fair
picture of conditions with regard to wave sh9ck and splash.
Conclusions.
Although data are incomplete, the following conclusions seem
warranted:
1. Although greatly disrupted by the presence of both clear-
cut and obscure mOdifying factors in the habitat, there seems to be
a general pattern of distribution far the organismS studied.
2. The degree of exposure of a platn vertical rock surface
to wave action and splash has a definite effect on the distribution
of gastropods and cirripeds in Zones 1 and U:pper .. 2. in the. rooky in-
tertidal area.
,. The amplitude or height of the vertical distribution
belts for the species concerned varies directly with the degree of
exposure to wave action and splash. Conversely, the greater the pro-
tection from waves and. splash, the more these distribution belts are
compressed, even to the point of disappearance.
4. In the cases of ACmael digitalis, A. scabra, and LittoriQ&
scutulata, there is a positive correlation between degre, of expo-
sure and the numbers ot individuals present per unit area.
5. Although counts on High and Hot tockS did not extend low
enough to prove the point, there 1s a suggest~9n in the data that
Balanus glandula flourishes equally well in both exposed and protec-
ted areas, Whereas Chthamalus fissue does better in quiet wate~.
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.APPENDIX
TABLES 1-4
TABIE 1
.r'" !!mil~
• .. ~. L. A. A. .Q. B•Sq. No. planaxls scutulata digitaUs soabra f'lssus glandula
1 2 0 0 0 0 0
2 0 0 0
'a
0 0 0
3 2 0 0 0 0 0
4 1 0 0 0 0 0
5 2 0 0 0 0 0
6 0 0 0 0 0 0
7 1 0 0 0 0 0
8 1 0 0 0 0 0
9 1 0 0 0 0 0
10 0 0 0 0 0 0
11-. 0 0 0 0 .0 0
12 1 0 0 0 0 0
13 1 0 1 0 0 0
14 2 0 1 0 0 0
15 0 0 0 0 0 0
1.6 1 0 1 0 0 0
11 0 0 1. 0 Q 0
18 0 0 5 0 0 0
19 1 1. 5 0 0 0
20 1. 0 3 1 0 1.
21 0 0 7 0 0 1.
22 0 o· 10 3 0 0
23 0 0 , 0 lll. 27
24 1 0 10 2 19 44
25 0 0 11 5 13 46
26 0 0 2 12 20 61
27 0 0 8 3 28 77
28 0 0 8 1. 28 81
29 1 0 10 2 43 119
30 0 0 9 2 49 81.
31 0 0 12 1 57 103
32 1. 0 9 1 68 148
33 0 0 12 8 76 189
34 0 2 25 14 169 214-
35 0 94 75 11. 83 696
36 0 72 69 11 109 679
31 0 36 62 18 136 535
38 0 6 42 26 85 331
~ Q .:s l§ .12 -.:zg 106
The bottom of' square 39 1s 6 f'eet above 0 teet t1de level.
Square 39 contained 13 Mytl1US calltornlanus.
·~
•
TABLE 2
~ BOCK
L. L. A· A. c. B.Sq. No. p1ar.xis scu'tulata digitalis, scabra tissue glandula
1 1 0 0 0 0 0
2 4 0 0 0 0 Q
3 0 0 0 0 0 0
4 2 0 0 0 0 0
5 2 0 1 0 0 0
6 4 0 2 0 0 0
7 1 0 0 0 1 0
8 6 0 0 0 1 0
9 5 0 0 0 2 0
10 4 0 4 0 4 4
11 1 0 1 1 2 5
12 0 1 2 0 9 18
13 1 :5 8 3 44 46
14 0 4 16 5 73 122
15 1 16 24 U. 91 223
16 0 11 20 8 92 258
17 0 14 31 4- 61 211
18 1 24 35 15 62 231
19 0 16 26 17 63 178
20 0 14 35 21 78 248
iJ: 0 ~ 52 gg, ~ 452
Bottom ot square 21 1s 6 teet above 0 teet tide level.
YaDl very small 11ttor1nes not counted between squares 10-14 1nclusive.
TABLE 3
MURPHY I S ROCK
-
L. ~. A. J:. A. Q. B.
Sq. No. planaxis 8cutulat.. digita11s scabra pelta tissus glaid.lQI.
1 1 0 0 0 0 0 0
2 0 0 0 0 0 0 0
:5 5 0 0 0 0 0 0
4 1 0 0 0 0 0 0
5 4 0 0 0 0 0 06_ 1 0 0 0 0 0 0
7 0 0 0 0 0 0 0
8 1 0 0 0 0 0 0
9 0 1 1 0 0 0 0
10 0 13 7 1 0 22:- 1
11_ 0 16 11.. 0 0 87 64
12 0 36 23 4 0 351 245
13 0 72 16 6 0 961 519
14 0 43 5 9 :5 1500p1us 818
~ Q .D ...Q 2- Q See note
2 teet ot rock surface extending 2 feet above square 1 cont.a1ned 1
L. plana:xla.
Square 14 oontained 2 Tetraollta squamesa rubesoeps.
Square 15 contained 14 1,• .a. rubescens.
The barnaole count tor square 15 was estimated to be approximately.
the same a8 tor square 14.
The bottom of square 15 1s 3 1'eet above 0 teet tide level.
TABLE 4.
SNAD~
~. !to Ao A. "g .. 12·Sq. No. plmaxis scutu,1ata d1gital.is scabra tissue glandula
1 1 0 0 0 0 0
2 1 0 0 0 0 0
3 1 0 0 0 0 0
4 1 0 0 0 0 0
5 1 0 0 0 0 0
6 4 0 0 0 0 .0
7 2 2 0 0 0 0
8 5 1 0 0 0 0
9 1 1 0 1 0 0
10 See note
11 0 12 1 1 0 9
12 0 9 1 1 1 13
n Q ..!! 2 g i .u
-
Square 10, wh1ch was taken at the same 1evel ,s square 9, contained
2 b. planax1s, 10 L. scutulata, and 1 l}. g1andula.
The 5 teet ot rock surface above square 1 contalned no organ1sma.
Square 13 contained 2 1impets ident1f'led as &. digitalis x A. pelta.
The bottom ot square 13 1s 4.5 teet above 0 feet tide 1evel.


The distribution of cirripeds and gastropods on plain vertical rock surfaces in the upper intertidal and splash zones

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The distribution of cirripeds and gastropods on plain vertical rock surfaces in the upper intertidal and splash zones

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