Johnson 1
ABSTRACT
The distribution of twelve supralittoral lichen species was
investigated on the southern shores of Monterey Bay, California
and related to their exposure to sea-water spray, aspect to the
sun, and tidal height. Percentage cover was determined using a
pin-hit technique. Tidal height and exposure to sea-water influence
the distribution of several species, while aspect only affects
one species. Aspect limits the distribution of Acarospora
schleicheri (Ach.) Moss. to south-facing slopes, and influences
the total percentage cover of other lichens. Some species in¬
vestigated reflect different degrees of tolerance to salt water.
Caloplaca bolanderi (Tuck.) Magn., Lecanora pinquis Tuck., Lecanora
phragmites Tuck., and a pyrenocarpus lichen appear most tolerant
to salt water exposure. The physical effects of waves may prohi¬
bit lichens from settling below 1.5 meters above the red alga
Endocladia muricata (Post. & Rupr.) J. Ag., mean height approxi-
mately 1.2 meters above zero tide level. No upper limit was observed.
INTRODUCTION
Though marine lichens have been studied for many years and
their distribution described and quantified on numerous European
shores, sparse data exist on the lichens of Monterey Bay, central
California, or those inhabiting the Western coast of North America.
Two early papers contain descriptions of local lichens, but lack
quantitative data on their distribution. Peirce (1899) investi¬
gated the nature of the association of alga and fungus in Ramalina
reticulata, Usnea, and Sphaerophorus globiferus collected in
Pacific Grove, but did not mention their distribution. Wheeler
Johnson 2
(1938) compiled a species list of saxicolous and lignicolous
lichens collected on Point Lobos Reserve, California, 5 km south¬
west of the most southern of the study sites in this paper.
The purpose of this paper is to describe in detail the species
distribution of some lichens in the supralittoral zone of the
rocky shores of southern Monterey Bay. In the supralittoral zone,
defined by Weddel (1875) and more recently by Fletcher (1973),
lichen thalli are seldom, if ever, immersed by waves, but appear
to favor at least occasional sea-water spray. Only saxicolous
lichens were surveyed, although Arthopyrenia sublitoralis (Leight.)
Arnold is known (Kohlmeyer, 1969) to grow on the shells of limpets
and barnacles in this region. Distribution of twelve species of
lichens was related to variations in physical and environmental
parameters.
Exposure to wave action was one parameter investigated. The
term exposure describes the magnitude of waves, splash, and spray
generated by the interaction of wind and numerous environmental
factors on a shore. Exposure values can be conveniently determined
from observations of the dominant marine algae, and are therefore
biologically rather then physically based for the purpose of this
paper. Marine animals are not used as exposure indicators because
of the uncertain effects of sea otter (Enhydra lutris) predation
upon local invertebrate populations. At certain depths, deprada¬
tions of populations are clear, but in the mid and high intertidal
zones populations may bein crevices and other refuges safe from
otter predation.
The distribution of supralittoral lichens is further related
Johnson 3
to variations in aspect to the sun and tidal height.
METHODS
A number of north- and south-facing rocks, with up to 10
meters difference in vertical height, situated in varying ex¬
posures located between Pt. Pinos and Monterey Wharf #2 on the
Monterey Peninsula, California (Lat. 36° 38.2', Long. 121° 53.5')
were investigated during May 1982. Generally, high rocks were
pinnacle-like or eroded and fissured boulders; low rocks were
more rounded but differed from high rocks mostly because they
faced the sea or were grounded in sandy beaches.
Exposure ratings were based on Ballantine's exposure scale
(Ballantine, 1961), modified using the following dominant and
equivalent species of algae (I. Abbott, personal communication,
1982):
1. Extremely exposed shores.
Alaria abundant.
2. Very exposed shores.
Laminaria at minus 2.0 ft. tide level.
No Alaria.
Hesperophycus, Fucus common.
3. Exposed shores.
Laminaria at minus 2.0 ft. tide level.
Hesperophycus, Fucus, Pelvetia common in bands
or zones.
Egregia.
4. Semi-exposed shores.
Laminaria
dropping out, seen in occasional patches.
Hesperophycus dropping out.
Pelvetia less common than in 3.
Fucus only found occasionally.
5. Fairly sheltered shores.
No Laminaria, Hesperophycus.
Pelvetia occasional.
Fucus rare (in patches).
6. Sheltered shores.
Only Pelvetia.
7. Extremely sheltered shores.
No permanent brown algae.
This exposure scale is not a simple mathematical scale. The inter¬
Johnson 4
cepts are at convenient, but not necessarily equivalent, intervals.
Therefore, a site given an exposure rating of 2 is not twice as
exposed as a site rated 4.
The locations of the seven study sites on these shores are
given in Fig. 1. Substrates in sites 1 - 5 are composed of granite,
while those in sites 6 and 7 consist of congrete,
Once the study sites were selected a technique was developed
for sampling percentage cover of lichen species. Previous research¬
ers (Ferry and Sheard, 1969; Fletcher, 1973) agree that percentage
cover is the best method for sampling and assessing saxicolous
crustose and foliose lichens which dominate rocky shores. However,
no previously developed sampling method proved wholly appropriate
to my study sites, as explained below.
Fletcher (i973) surveyed marine lichens by placing transect
tapes along the shore contour, relating transect positions to tide
levels. He sampled lichen with a 10 X 10 cm transparent square
ruled into 100 1 X 1 cm squares. Each 1-cm square over 1/2
occupied by a lichen thallus was counted as 1% cover of that
species. A 50 cme frame was laid at 1/2-m intervals along the
transect tape, and five grids were counted, one in each corner of
the frame, and one in the middle.
This sampling method applied to my study sites proved in-
effective because many lichen species shared each 1 X I cm square.
The thalli of lichens are very small, grow in patches, and often
form mosaic-like patterns containing numerous species. Therefore,
a pin-hit technique proved to be the most accurate method of assess¬
ing percentage cover of individual species.
Johnson 5
The transect method was deemed inappropriate because it
resulted in frames filled or partially filled with flowering
plants and barren rocks, or subjectively selected. Further¬
more, transect lengths varied considerably amongst study sites,
so a standard sample size could not be obtained. Similar draw¬
backs were inherent in the sampling methods employed by Ferry
and Sheard (1969).
For each of the seven exposure areas, four subareas were
identified: north-facing high, south-facing high, north-facing
low, and south-facing low slopes. Low study sites began at the
lowest thalli of Lecanora pinguis, generally if on north-facing
rocks on the seaward side. Low sites extended 1.5 vertical meters.
The lower limit of the high sites was the elevation at which angio¬
sperms, notably Mesembryanthemum, became dominant. In each sub¬
area, six 50 cme or larger rocks were selected for sampling
according to the following criteria:
1. Aspect - a compass reading within 20° of due north
or due south. North-facing rocks faced the sea
in all sites.
2. Slope - 45° -
90°
3. Proximity to sea - the six quadrats fulfilling the
above criteria and closest to the ocean were
selected for percentage cover analysis.
A 50 cm clear plastic flexible sheet (quadrat) with five
10 X 10 cm grids drawn with various orientations at the four
corners of the plastic and in the middle was placed on a rock.
To insure random orientation of the quadrat, a sheet of black
plastic was laid on top of the clear plastic and both were posi¬
tioned on the rock. For coverage counting, the black plastic
Johnson 6
was removed. Each grid contained 100 dots spaced 1 cm apart on
all sides. To assess percentage cover, the lichen species found
under each dot was identified and recorded as 1% cover. For
each subarea, 3000 points were pooled and analysed to obtain mean
percentage cover values for each species present. In all, 1200
points were counted in each exposure site, except in sites 6 and
7 where only north-facing low rocks were counted.
RESULTS
Analysis of data from the seven sites examined indicates
that six species occur in fairly constant positions in the supra¬
littoral zone.
The chi-square test of independence was performed to assess
the significance of differences in species richness between north¬
facing high rocks, north-facing low rocks, south-facing high rocks,
and south-facing low rocks. The results indicated that aspect is
not a significant factor influencing species richness. However,
when the richness on high rocks was compared with that of low sites,
it was apparent that tidal height influences species richness, on
seaward facing slopes. High rocks contain twice as many different
species than do low rocks.
Exposure also affects species richness. Using Ballantine's
exposure scale, it appears that richness decreases in extremely
exposed and very sheltered environments, with the greatest rich¬
ness exhibited in fairly sheltered sites, for both high and low
rocks (Fig. 2).
The chi-square test of independence for abundance shows that
north-facing rocks exhibit a significantly higher total percentage
Johnson 7
cover by lichens than south-facing rocks (Fig. 3). North-facing,
high rocks show the highest total mean percentage cover of any
subarea within a site.
Certain species are restricted to rocks of a particular aspect,
while others are not. Acarospora schleicheri (Ach.) Moss. only
occurs on south-facing, high slopes. It is present in all but
extremely exposed environments, and is most abundant on exposed
shores (Fig. 4). Conversely, Physcia phaea (Tuck.) Thoms. and
Buellia sp. were found only on north-facing high rocks, in very
low abundance on fairly sheltered shores. The distribution of
the other species investigated appears unrestricted with respect
to aspect.
The full influence of tidal height upon lichen distribution
in areas of varying exposure could not be objectively compared
because the vertical range of available substrate for lichen
colonization differed from site to site. In sites 6 and 7, no
high rocks existed, while in site 4 boulders heavily encrusted
with lichen occur 10 meters above the sea. Where high substrate
was available (sites 1 - 5 ), lichens were abundant.
Some species exhibited a preference for substrate within a
certain vertical range. Aspicilia sp. was most prevalent on high
rocks in exposure areas 2 - 5 (Fig. 5). Only on very exposed
shores was it counted on low rocks. Pyrenocarpus lichen (Fig. 5)
prefers low, north-facing, semi-exposed environments. It was
found even in extremely exposed sites, but reached a peak in
abundance in semi-exposed site 4. Based on the distribution of
these species, this pyrenocarpus lichen appears to be more tolerant
Johnson 8
of sea-water spray than does Aspicilia sp.
Although the height of the highest rock containing lichen
varied amongst sites, the height of the lowest lichen thalli re¬
mained fairly constant with respect to the red alga, Endocladia
muricata (Post. & Rupr.) J. Ag., in all exposure sites. Height
was measured above the top of the Endocladia zone, which occurs
between 1.0 - 2.0 m above zero tide level, using a meter stick
and surveyor's tape. The lowest thalli of L. pinguis or Caloplaca
bolanderi occurred in all exposures between 1.5 and 3.0 meters
above the Endocladia. Perhaps below that height, these species
cannot survive wave action or competition for substrate with
algae.
The distribution of several lichen species may be correlated
with areas of particular exposure to wave action.
Lecanora pinguis, while one of the most common lichens, is
rare on more sheltered shores (exposures 6 and 7) but becomes more
abundant on more exposed high rocks (exposures 1 and 2, as shown
in Fig. 6). Its greatest abundance on north-facing slopes occurs
in exposure site 3, while on south-facing rocks, L. pinguis is most
abundant in very exposed sites (exposure rating 2).
Another species of the same genus, L. phragmites Tuck.,
exhibits the opposite distribution pattern. L. phragmites is rare
or absent on exposed shores, but becomes progressively abundant on
sheltered shores (Fig. 6). It is the dominant species on north¬
facing low rocks in fairly sheltered (exposure 5) to extremely
sheltered (exposure 7) environments. L. phragmites occurs in low
abundance on high slopes and was not encountered on low south-facing
Johnson 9
rocks.
Some lichens occurred in low numbers at most exposures.
and in the case of Caloplaca bolanderi, this species seemed
to favor low quadrats rather than high quadrats of the same
exposure (Fiq. 4).
The distribution of the two species of Niebla indicates
that they are semi-terrestrial. The Niebla species have a pre-
dominantly landward distribution, often sited on residential
garden rocks along the shore in Pacific Grove, and are encounter-
ed in positions sheltered from sea-water spray, such as crevices
or lee-sides of high rocks.
Species C is the most widespread of these semi-terrestrial
species in the supralittoral zone. It was counted in exposures
ranging from very exposed to fairly sheltered. N. combeoides
(Nyl.) Rund. & Bowl. and N. homalea (Ach.) Rund. & Bowl. were
found in semi-exposed and fairly sheltered high sites, with N.
homalea more abundant on north-facing slopes and N. combeoides
more abundant on south-facing slopes (Fig. 4).
Still other species occurred so rarely or in such special¬
ized niches that they were not included by the sampling method,
Roccellina condensata (Darb.) Follm. was only found in exposed
and fairly sheltered areas (study sites 3 and 5) in the steep
crevices of high rocks. Accordingly, it was never encountered
in a quadrat. Where R. condensata was observed, it grew abundantly
in thick, dense patches. The presence of this species on the
Monterey Peninsula is a new record for North America,
Johnson 10
DISCUSSION
The results of this study show that aspect has an important
effect in limiting the distribution of Acarospora schleicheri,
which may be considered photophilic, and influences the total
cover of other lichen species. Aspect mainly influences sunlight
exposure, substrate temperature and moisture. In general, south¬
facing rocks receive more sunlight than do north-facing rocks.
The larger amount of heat generated from longer periods of sun¬
shine causes faster evaporation on south-facing rocks. Following
wetting by wave-action or fog, south rock faces tend to dry out
more rapidly than north-facing rocks of the same exposure rating.,
Aspect could account, in part, for the higher percentage cover
documented on north-facing rocks.
Factors other than aspect which could influence the dampness
of the supralittoral zone include substrate slope, fog, tidal
height, wind-speed, wind-direction, and proximity to sea. No
attempt was made to quantify the dampness of the substrate at
various exposures.
The distribution patterns of the supralittoral lichens invest-
igated reflect different degrees of tolerance to salt water spray.
the species found in extremely exposed environments (exposure rating
1), namely Caloplaca bolanderi, L. pinguis, L. phragmites, and
pyrenocarpus lichen being the most tolerant. These results contrast
with the conclusions of Ferry and Sheard (1969) on the Dale Penin¬
sula, England, that none of the nearly 50 species studied show a
preference for shores of any particular exposure. However, these
workers suggest that exposure to salt water may fulfill a nutritional
Johnson 11
requirement, not create a stress, for some supralittoral lichen
species.
Species distribution may be further complicated by substrate
competition between species with similar tolerances to salt water.
In low areas and very exposed areas, lichens must also compete
with algae for substrate. At Pt. Pinos, the extremely exposed
study site, the green alga Prasiola occupied the high rocks, where
lichens could be expected in less exposed areas. It appears that
on extremely exposed shores wave action is so strong that sufficient
salt water is carried to even the highest rocks allowing the
establishment of algae, some well above the normal vertical range.
Prasiola and L. pinquis were observed growing side by side on high
rocks at Pt. Pinos, but judging from relative abundance, the alga
possesses a competitive advantage. It should be noted that algae
have much faster growth rates than do lichens.
The physical effects of waves may prohibit lichens from
settling below the tidal heights documented. No upper limit was
observed here, but Wheeler (1938) indicated that Lecanora pinquis
occurred at 40 ft. above sea level at Pt. Lobos
(a very ex¬
posed site).
No grazing on lichens by marine organisms was observed in the
field. However, hundreds of ladybugs were seen crawling on various
lichen species in study sites 1 - 3 during late May. The ladybugs
appeared to be grazing, probably on small organisms dwelling on
lichen, but no gut analyses were performed to verify this observa¬
tion.
C
Johnson 12
ACKNOWLEDGEMENTS
I am grateful to the faculty of Hopkins Marine Station,
particularly to Dr. I. Abbott for inspiration and encouragement,
and Dr. James Watanabe and Charles Baxter for statistical advice,
I am also indebted to Dr. Mason Hale, Dept. of Botany, Smithson¬
ian Institution, Washington, D.C. for species identification.
Johnson 13
REFERENCES
Ballantine, W.J. (1961). A biologically-defined exposure scale
for the comparative description of rocky shores. Field
Studies (1-2) 1959-1968: 1-18.
Colman, J. (1933). The nature of the intertidal zonation of plants
and animals. Jour Marine Biol. Assoc., U.K. (N.S.), 18: 435-
476, figs. 1-15.
Ferry, B.W. and J.W. Sheard. (1969). Zonation of Supralittoral
lichens on rocky shores around the Dale Peninsula, Pembroke¬
shire. Field Studies (3) 1969-1973: 41-55.
Fletcher, A. (1973)? The ecology of marine (littoral) lichens on
some rocky shores of Anglesey. Lichenologist, 5: 368-400.
Fletcher, A. (1973)? The ecology of some maritime (supralittoral)
lichens on some rocky shores of Anglesey. Lichenologist, 5:
401-422.
Johnson, T.W. and F.K. Sparrow. (1961). Fungi in oceans and
estuaries. Hafner Publishing Co., N.Y., N.Y. pp. 1-26.
The role of marine fungi in the penetra¬
Kohlmeyer, Jan. (1969).
tion of Calcareous Substances. Am. Zoologist, 9:741-746.
The nature of the association of alga and
Peirce, G.W. (1899).
fungus in lichens, proceedings of the Ca. Acad. of Sciences
3d Ser. Botany (1): 207-240.
Excursion lichenologique dans l'ile d'Yeu
Weddel, H.A. (1875).
sur la Cote de la Vendei. Mem. Soc. Nat. Sci. Naturelle et
Math, Cherbourg, 19: 251-316.
Wheeler, L.C. (1938). Lichens of Point Lobos Reserve. Bryologist (41):
107-113.
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FIG. 2
SPECIES RICHNESS ON SHORES OF VARIOUS EXPOSURES
10
9
8
TOTAL
NUMBER
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PRESENT
4
3
2
5
3 4
6
2
extremely
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EXPOSURE SCALE
A high sampling sites
low sampling sites
extremelj
sheltered
FIG. 3
CHI-SQUARE TEST OF INDEPENDENCE FOR
LICHEN ABUNDANCE
X = TOTAL MEAN % COVER FOR EACH SUBAREA
CI= 95% CONFIDENCE INTERVAL
SOUTH
NORTH
66.58
39.43
HIGH X
102.0
6.88
22.24
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