Marroystis Fyrifers giant kelp, is a brown algae that forms a surface
canopy along the coast of North America from Baja California to San
Francisco, in South America, southern Africa, and southern Australia (Abbott
and Hollenberg 1975) It displays a typical Laminariles life cycle, with
alternation of generations from a microscopic, sexual gametophyte stage to a
large, asexual sporophyte stage (figure 1). Special fertile fronds called
sporophylis, located near the base of the kelp, release free-swimming spores
which attach to the substrate and form gametophytes. After about a month
of development (Deysher and Dean 1986), male gametophytes reease
biflagellate sperm which fertilize an egg attached to the female. The
porophyte begins growth attached to the female gametophyte. (see North
1974, Dayton 1935 for more details) Kelpforests dominated y Mayss
pyers have long been a subject of great interest because of their economie
and ecological importance. Since the advent of SCUBA, many researchers
have designed field experiments attempting to mode dyamis othe elp
forest. This has proved to be an extremely difficult task due to the complex,
interactive, and unpredictable nature of this environment.
To understand the kelp forest, one must begin with an understanding
of Marystis itself. Although studies are being carried out every day in
kelp forests around the world, thousands of questions are still unanswered.
Many inwestigators here in California have chosen to narrow down the
questions een arther, addressing the microscopie stages o theyss
life cycle. What are the dynamics of gametophyte recruitment and survival:
Whatfactors physical or environmental, control mortality? Many methods
for etudy have been developed, a few questions have been answered, but
many more remain. For example, i Mryss is fertile year round
(Anderson and North 1956) releasing spores at arate o 500000
(Anderson and North 1956) ydoes reritmet vsi
sporophytes vary so significantiy with time of year? (Harris et al 1984
Layton et al. 1984, Ebeling et al. 1985, Reed et al. 1983) Why does only 1 in
10 gametophytes survive in the field? (North 1974) Andhy dona
estimated 2 of visible sporophyte recruits ever reach the surface? (Dayton
et al. 1964) Some parameters needed for success have bee determined
Deysher and Dean (1986) define arecruitment ino for nat
production ei sporophytes as temperature below 16. 30C and irradiation
levels above 0.4E m-2 day-1. Similarly, North (1974) refers to an
unquantifiedenvironmental turnstile betee
appearance of juvenile sporophytes. Devinny nose (197
that 10 mg em-lof sediment causes significant mortality to gametophytes.
and Luning and Neushul (1978) havedetermindritia lg
gametophytic reproductive success. Grazers such as seaurchins see Ebelin
et al. 1935) and fish (Neushul and Haxo 1933 have
mortality to adult and juvenile sporophytes, and some researchers have
recenty begun to attempt to determine the effects of grazers on the
gametophytic stage as well. (L. Holts, pers. comm., D. Antonio, pers. com
Here is where my experiment fits in, as a small piece of a verylare and
cmplex puzzle
in the ryss pyrierdominated elp
LA, one oi the mst abundant grazers are turban snails of thegenus
Even though leguss preferred food is adult Myss frons andt
Watanabe 1934) the effect of Tegu grazing on the adult plant has been
asumedtobeminr Theeets oonthemiroscopie stages o
Maroysts,however, has not been determined.
Thetw most common species of Tegua in the Hopkins kelp forest
are Trunes which is most abundant from O-6 m, and T pullig which is
abundant in deeper water. A third congener, T monterey is less common
but is found at depthe similar to T pullige (Lowry et al. 1974, Watanabe
19845) Although the majority of the snails are found up on kelp plants, a
substantial number can also be found on the substrate. Densities of these
snails on the substrate has been quantified by Watanabe (1982) and Harroid
et al. (1988).
lused copper-painted patio stones as experimental Tegua -exclusion
plots. Copper has been used effectively by a number of experimenters (eg
Cubit 1975, Robles 1982, Johnson, in prep.), and recently a pilot study was
conducted at Hopkins MarineSti yae
potential effectiveness of copper strips as barriers to Tegula spp. (I.
Leichter, 1989, personal communication.)
Torunnea is very abundant on the substrate in the shallow subtidal.
Watanabe (1932) found mean densities of 376 4/-3.8(SE) Tbrunea m
in this depthrange Kelpplant density at this depth is considerabyowe
pereobserv) Byplacingexperimental pots in thekepforestatdepths o
75mand 2.4 m,I hoped to determine whether Tegula grazing pressure
waried with depth.
Matariäls and Methais
The technique of artificial seeding of Mroyss has been well
deweloped and used extensively. My procedure was similar to that used by
number of experimenters, including Neushul (1963), Anderson and North
(1969), Deysher and Dean (1986), and Reed (in prep.). Gametophyte cultures
were grown on frosted glass slides (Fisher fully frosted cytology slides) at
densities from 33 mm2 to 180 mm2 Glass slides weree
settling surface because they are easily manipulated and they facilitate
microscopic viewing of the gametophytes. Ripe sporophyseed
from the kelp bed off of Hopkins Marine Station Spore release as achieved
by cleaning 20 or so ripe sporophylls with a paper towel to remove any
epiphytes, and then soaking the sporophylls in chilled filtered seawater for
2-3 nours. The density of the resulting spore solution was measured usin
nemacytometer. Densities used for plating ran from 8.1X10sp
to 5.9 X 100 spores mi-1. The solution was poured 3 to 4 cm high in a tray
holding trosted glass slides. Thesporeswa
befère the trays were washed in frech filtered sea water. After three days
the gametophytes were large enough to clearly count and identify under a
4 objective of a compound microscope. Gametophyte survivorship was
measured by scanning 15 evenly-spaced25 m fields onidO
the middle inch of each slide was ezamined, leaving an inch on each side to
manipulate the slides in the field. All slides were kept subered
filtered sea water in a Plexiglass slide holder during viewing. Table 1 shows
te density of spores in solution that correspond to density of gametophytes
seenon the slides three days late.
Jides used for laboratory controls were kept in the sttling trays. T
water was changed every 1-3 days No special temperature or light regime
as usedcultures were subjeed t o ay-lig
températures of about 6OF No extra nutrients wre addedonthe
assumption that the filteredsea water from Monterey Eaywasriheg
in nutriente not to limit development.
All experiments began three days afterpoe settement.
jeleperients
All field experiments were done in the keip beds off of Hopkins
Marine Station of Stanford University in Pacific Grove, CA, USA (360 36 .
121054"
In the field slides were held by surgical tubing attached to 25.4 cm X
15.2 cm X 0.6 cm Plexiglass sheets. The Plexiglass was attached with 2
masonry screws to circular concrete patio stones, 30.5 om diameter and 5.1
em thick. For each set of three treatments, I painted the entire outer
circumference of one patio stone with copper paint (Interlux Copper-Lux
Antifouling Bottom Paint, 66 58 cuprous oxide), left one bare, and painted
one in alternating 450 arcs of copper paint and bare concrete. Each patio
stone could hold up to 8 microscope slides. (Figure 2)
For the first set of experiments, 3 replicates of 3 patio stones each
wereplaced on the substrate in the Hopkins kelpforestatdephE
setoi patio stoneswswithin 25 mor less of an aduit Msrsts. Al
threereplicates r lated ithin 3 mofoneante inteopethat
this would minimize beten-site diffee 4 gamtidepe
at adensity of 32gametophytesandie
eich patio stone The clean slides serwed as a control to determine any newy
gametophyte recruitment that would have occurred during the experimental
period To gametophytesides and one controide re leed afte
days then after 6 days in the field. New gametophytes (at a density of 59.2
gametophytesmwrept
and they were collected after 5 and 7 days. Data from the two experiments
were combined for analysis.
The second set of field experiments was carried out a week later at 2.4
m. Only the full copper-treteane
this time replicated 3 times (Sites 45, and 6) All replicateswereagain
within 25 m or less of an adult Marraystis, and within 13 m of one
another. 8 gametophyte slides (density 603 gametophytes m-2) we
placéd on each patio stone. Two slides from each stone were collected after
14 hours, 2 days, 5 days, and 7 days. No recruitment control slides were
used
As an additional control during each field experiment, 2 extra
gametophyte sideswrearieuteiea
and counted at the end of the diveTran
additional mortality over slides remaining in lab. Other experimenters have
toufi similar resus with transport controls (Deysher and Dean 195e
in prep.)
lab experiments
ne lab experiments wre carrid out in asmall aquarium divided
into three equal parts. Water could pass from one section to the next, but
sfails could not 2 gaetpyeideedin
tubing woven through a 7.6 cm X 15.2 cm X 06 cm sheet of Plexiglass. 5
legus brunnes were put in one section, 5 T pulige in another, andthe
third was leit free of snails as a control. The slides for the first experiment
were plated at a high density of 181 gametophytes m-2Thenai
removed after three days andremaining gaee
econdexperimentusedidesofgametpye denity of 32m-
Gametophyte densities were recorded after 4 hours, then again when snails
were removed after 24 hours
ses table erperiments
The same patio stonePlexiglass sideodee
used in the sea table experiments. They were placed at the bottom of an
outdoor fresh-running sea water 9lemX9lmXieas
aquarium. Thefirt epeimes ai uaittve oe
ettectiveness of the cpperpaint as a barrier t Tua Approximately 30
grams (wet weight) of adult Mfo
each patio block. 5 Tegula brunnea and 5 Tegula pulligo were placed in the
sea table near the patio stones. Observations were made several times a day
After 5 days, all of the Macræystis from the untreated and half-copper
stones had been consumed, while the Macrocystis on the copper-treated
stone was untouched. Snails were never observed on the copper stone, while
they were almost always present on the other two. This assured me of the
effectiveness of the copper paint, and I went on to the field experiments
The second sea table experiment used slides plated at a density of 600
gametophytes mi-4. 5 T brunnea and 5 T pulligo were placed near the
stones and left to graze for 7 daysade
after 2, 5, and 7 days.
FESITS
lab experiments
Results trom the lab experiments showthat grazing by Tegula does
cause mortality to Marystis gametyes ne
Mortality on control slides was minimal during the course of the
experiments while over 90 of gametophytes exposed to snail grazers
disappeared within 24 hours. This broughtoveral gametophyte density
doun trom about 180 gametophytes mi2 toless than 10mm-2 (figure 3
legula exhibit typical grazing behavior (Hickman and Morris, 1985) when.
exposed to gametophytes on a frosted glass slide. Theyscrapetheside with
their radulae in a semi-circular pattern, leaving characteristic trails in the
gametophyte laThese traiswreoeed on i
Tegua in the lab.
ja table erperiments
lea table experiments also showed effects of Tegula in Tegusa
aeiblearas Mortalita a a
however, was higher than in the lab. After 3 days in the sea table, 638
mortality was observed on the copper-painted stones, compared to 958
(about 3 gametophyteontu i 4) D
lack of time and sea-table space this experiment was not replicated.
Statistical analysis wastherefore not performed.
Feid experiments
Recults from the field experiments at 76 m can be seen in figure
For clarity ofpresentation data from the two temporally separate
experiments at 7bmare combined. Data was analyzed using a 2-way
analysis of variance from the IBM software package, SPSS/PC (Table 2). To
simplify analysis, data from the half-copper treatment was not considered
(see discussion). Statistically significant (pe05) differences were seen
between copper-treated and untreated plates. Significant (pe.05)
difierences were alsoseen between individual replicates of the ame
treatment, with site 1 always having higher survival than site 3.
The results of the experiment at 2.4 mare presented separately in
figure 5. It is clear from the figure that no difference between treatments
wasfound in this experiment and bothtreatments experienced over 95
mortality within a week, resulting in an overall gametophyte density of less
than 2 gametophytes mmTherefore noatistia test were done.
listussia
Characteristi radulr grazingmarksw anu
elides trom Tegua-accessible patio stones in the field. This implies that
Tegula does notonly eat gametpye unde ontoed laoratory
conditions but will et them off glasssides in the field as well. Significant
differene beteen treatments atthe 7m site show that this grazing
behawior could ause ome of the observed gametophyte mortality. Tgs
howeweraarromthedominana diatinggametophyte motality
or urwival in my experiments. Even in the plots where Tegs was kept
out, almost 95 mortality was observed after a week. It is estimated that a
male gametophyte must belocated no further than m away froma
female for successful fertilization. (Reed in prep.) So if gametophyte
densities start at less than 40 m25 mili
peent any lateaeodeelet
Assuming pibe 5 o the maity oeed
what could have caused the other 90? I attribute agood deal of this
mortality to environmental factors. At 7.6 m, surge caused the plates to be
scoured by both sediment and algal fronds. Site 3wionise
showed the highest mortality of the 3deepsites, was found covered by a
drifting adult Maroyss on day 6. Asstated beore 10mg-
sediment can significantly affect mortality (Devinny and Volse. 1978).
l believe environmental pressures caused most of the mortality on my
plates in the experiment at 2.4 m. After 7 days, gametophyte density was
lowered so drasticallthatpy uiten wouave een highly
unlikely Surge was heavy every day of the week-long experiment. Large
tragments of algae carried by the surge lowered underwater visibility
considerably and wereseen to be souring the plates during all dives. Low
light scour and water motion could all have contributed to mortality.
Weather conditions such as this clearly indicate the viability of Deysher and
Deans (1985) 'recruitment window hypthesis.
Grazers other than Tgua could also have played a significant role in
gametophytemortalityinpateua
amount of grazing presue experiened by animals othe than is
unknown Copper paintdoes notserve as a barrier to the sea stars stes
o aser Both of these grazers were seen on a number of the patio stones
at 7.5 m, including all three treatments at site 1. The only animal observed
on the experiment at 2.4 m was a Pisaster giganteus on the copper-
treatmentatite 4.
The question of wte obsevedes wedue
enhancement effect of copper on gametophyte survival have not been
anewered unequivocallyTpie
strongly point to a rejection of this hypothesis. First, copper is known to
inhibit gametophyte growth even at concentrations as lowas 100 pp (Smith
and Harrison, 1979). No evidene of enhancement of any kind has been
tound. Second survivoipon al-coppee di
predictible pattern, as it would if copper was affecting gametophytes
directly. Sometimes this treatment mimicked the effects of the full-copper
treatment sometimes it mimicked the bare concrete treatment, and
sometimes it fell directly between the two. I believe that this is due to the
observed behavior of individual snails when encountering the half-copper
stones. Snails would climb onto the plate or avoid it, depending only on
hich area of the stone the snail first encountered
This experiment has shown that grazers have an effect on
gametophytesandwhaveomeonepose to understanding the
dynamics of the Macroystis life cycle. I am not, however, convinced that
legua snails havevital influence on gametophyte dynamics oi Marsts
the Monterey Eay kelp forest. I am convinced that they play a minor role,
and that they will eat gametophytes i they happen upon them. Te
definitive solution to the mystery of high gametophyte mortality will most
likely lie in a combination of factors, both physical and biological.
e obvious netp thisudy ud be to deteie
egula grazing plays in thenext lifetagesoMae
and juvenile porophyteLitequas d
of any grazers on these stages, even though grazing effects could be very
important Itis possible that physical factors control the observed high
mortality of gameto
lytes, while the hardier juvenile sporophytes that
remain are aifected more greatly by biological factors. Evidence for this and
manyotherhypotheseserineiai
produced
EIBLIÖGRAPHI
Abbott and Hollenberg. 1976. Marine Algae of California. Stanford
University Press, Stanford, CA.


rson, E. K. and North,
J. 1956. In situ studies of spore production and
dispersal in the giant kelp, Maystis In Proc Intl Seaweed Symposium
3-36.
Cubit. JD. 1975. Interactions of seasonally changing physical factors and
grazing affecting high intertidal communities on a rocky shore. PhD thesis,
Univ. of Oregon, Eugene
Dayton, PK., Currie, V., Gerrodette, T., Keller, B.D., Rosenthal, R., VenTresca, D.
1984. Patch dynamics and stability of some California kelp communities
Ecol Monog 54(3) 253-289.
Dayton, PK., 1985. Ecology of kelp communities. Ann Rev Ecol Syst. 16.2 15-
245
vadis pyrisera
Dean, TA. and Jacobsen, FR. 1984. Growth of juvenile
in relation to environmental factors. Mar Biol 83:301-311.
Devinny, J.S. and Volse, LA. 1978. Effects of sediments on the development
ot Macrecysts pyrifera gametophytes Mar Biol 48343-343
Deysher, L. and Dean, T.A. 1986. In situ recruitment of the giant kelp,
re
Maireryatia pyriiera. Ellects of physical factors. Journ Exp Mar Bio Ecol
103:41-63
Ebeling, A.W., Lauf, D.R., Rowley R.J. 1985. Severe storm disturbances and
reversal of community structure in a southern California kelp forest. Mar
Bio 34:287-294
Harris, L., Ebeling, A. Laur, D., Rowley, R. 1984. Community recovery after
storm damage A case of facilitation in primary succession. Science 224.
1336-1338.
Harrold, C. Wat
nabe . Lisin, S. 198 Spatial variation in the structure of
keip forest communities alongawave expoure gradient. Mar Ecol.
9(2) 131-156
Ti kman, C.S. and Morris, TE. 1985
Gastropod feeding tracks as a source of
du fa in analysis of the functional morphology of radulae. Veliger 27(4). 357.
30
1it, D. 1977. Population dynamics of Tegula and Calliestams in Carme
E wit
special reference to kelp harvesting. Master's Thesis, SFSU.
ison, L. in prep. The use of copper metal to manipulate mollus can
81 r5.
fiter, J. 1989, unpublished. Copper barriers as a potentially effective
nnique for excluding subtidal gastropods from experimental plots,
ighton, D.L. 1966. Studies of food preference in algivorous invertebrates
outhern California kelp beds. Pac Sci 20.104-113.
Wry, L., McElroy, A., Pearse, J. 1974. The distribution of six species of
ea tropod molluscs in à California kelp forest. Biol Bull 147.386-396.
henco, J, Gaines, S.D. 1981. A unified approach to marine plant-
bivore interactions I. Populations and communities. Ann Rev Ecol Syst
105-37.
ing, K. and Neushul, M. 1978. Light and temperature deman
s th and reproduction of Laminarian gametophytes in southern and
tral California. Mar Bio 45.297-309
reno, C. and Sutherland, J. 1982. Physical and biological processes in a
reaus pyriercty Ne ad
"ghul, M. Foster, M.S., Coon, D.A., Woessner, J.W., Harger, B.W.W. 1976. An
itu study oi recruitment grothand surviva  su
liniques and preliminary resultsPhycol 12:397-408
H. W.j. 1974. Mass-cultured Maoystisas a means of inreasing ke
s in nature. In 8th Int Seaweed Symposium 394-399
re, J. and Lowry, L. 1974. An annotated species list of the benthic algae
3.
invertebrates in the kelp forest community at Point Cabrillo, Pacific
7e,CA. Coastal Marine Lab, Ues, Technical Report

4. D. C., Laur, D. F., Ebeling, A. W. 1986. Variation in algal dispersal and
uitment. The importance of episodic events.Ecoi Mnog 5(4). 321-335.
Robles. C. 1982. Disturbance and predation in an assemblage oi herbivorous
diptera and aigae on Rocky Shores. Oecologia (Berl) 54.23-31
Smith. BM. and Harrison, F.L. 1979. Sensitivity of Maroystsgametophyte
to copper. Prepared for the U.S. Nuclear Regulatory Commission, NRC FIN No
20119
Watanabe, JM.1984a. Food preference, food quality and diets of three
herbivorous gastropods (trochidae Tegula) in a temperate kelp forest
habitat. Oecologia (Ber1)62:47-52.
„1984 b. The influence of recruitment, competition, and benthic
predation on spatial distributions of three species of kelp forest gastropods
(Trochidae: Teguta ) Ecol 65(3) 920-936
3




S
O






10
FIGURE 2: EXPERIHENTAL SLIDE HOLDER.
—
a

a






W
5
1. CONCRETE PATIO BLOCK
2. PLEXIGLASS
3. SURGICAL TUBING
4. MASONRV SCREWS ATTACHING
PLEXIGLASS TO CONCRETE
5. GLASS SLIDES
6. EDGE OF PLATE LEFT BARE OR
COATED WITH COPPER PAINT.
FIGURE 3: RESULTS OF SECOND LABORATORY TRIAL.
DRIGINAL PLATING DENSITY: 33 GAHETOPHYTES MH-2


30 -

60-
40 -

20

—

12 16 20 24
HOURS
...- tegula brunnea
-- —- tegula pulligo
control
100
80 -
60-
40 -
20
Figure t.Results of sea table experiment.
h=1 (this experiment was not replicated).
Uriginal gametophyte densities=59.2 mm-2.
—
—— lab control

----- copper-treated
-- —-. untreated


DAYS IN SEA TABLE
FIGURE S:GAMETOPHYTE SURVIVAL ON COPPER-TREATED VERSUS UNTREATED PATIO STONES AI 7.6 m.
ERROR BARS REPRESENT STANDARD ERROR.
100 4
30
—--COPPER-TREATED
50
—
UNTREATED

40

20

o
4 512 61
741
—
DAYS IN FIELD
« data trom days 2 and 6 caleulated from original plating density of 32.8 gametophutes mm-2.
t data trom dais f and 7 naleulated from orininal nlatina densities af 59 2 nametonbutes rom-?
—
FIGURE 6: GAMETOPHYTE SURVIVAL ON COPPER-TREATED VERSUS UNTREATED PATIO STONES AT 2.1m.
ERROR BARS REPRESENT STANDARD ERROR
DRIGINAL PLATING DENSITY: 60 GAMETOPHYTES MM-2
100
80 -
-— COPPER-TREATED
50
— — UNTREATED
40
20

o+
DAYS IN FIELD
Table 1: Density of spore solution corresponding to resuiting gametophvte
densities counted three days after plating.
bensity of spore
Derisity of
solution
gametphyteson
(epores mi-1)
slide (gsmetophytes
vhen gametophytes were used
mm 2)
32.8
8.1X 104
first 7.6 m. exp. 2nd lab exp.
second 7.6 m. exp, sea table exp.
1.7 X 105
59.2
2.2 X 105
60.3
2.4 m. experiment, sea table exp
5.9X 105
181
first lab exp.
TABLE 2 : Two-way ANOVA, showingthe effectof treatment (copper
untreated) and location (3 replicates located within 13 m of one another) on
gametophyte survival at 7.5 m. From IEMtatisti program
PC
sum of
degrees of
mean
signisicance
square
freedom
square
o f
main effect
23.046
7.682
4.316
018
9.275
9.275
treatment
035
5.212
2—
location
5.1
5.335
3.369
040
2-Way
treatment-location
2.92:
1.463 822
45

plained
25.972
5.194 2.919
042
residual
1.780 —-
— ——
32.035
total
— — —
— — —
56.007
23
2.522