115
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1123
Elaine Evans 3
roduction
The quantity of drift algae on a sandy beach is
constantly fluctuating. Residence time for the majority
the drift is brief, in that only about ten per cent
remains long enough to completely decompose, but while
remains it provides a major source of food and shelter
for organisms on the otherwise barren sandy beach.
ZoBell (1971) did a twelve year study on the dri
seaweed on San Diego County beaches, and made biweekly
inspections at low tides on forty-nine beaches. Estimates
were made of the quantity and major species compo
tion of
large depositions found on these beaches. My study.
in order to est
mate the poten
lal organic matter con¬
tributed by the drift on a sandy beach, attempts a
closer observation of similar factors in a 5-week period.
Elaine EvansL
on a relatively small sandy beach at Hopkins Marine Station.
in Monterey Bay.
Observations were made to determine changes in quantity,
class composition by bulk, potential organic input from
drift, and the quantity of dri
arriving on three specific
areas of the beach. Both this study and ZoBell's concur
ft deposited on the beach is
(i) that
the quantity of dr
related to the amount of off-shore growth, and to water
and wind movements as indicated by wave heig
ts; (ii)
that residence time of depositions of drift is a factor of
the high water levels which follow it; and (iii) that
slope of the beach chal
nges with large depositions of sand
(also linked to wind and water movements), and this affects
the quant
ties of drift remaining on the beach.
The beach studied has a west north west exposure, and
is flanked by rocks north and south. It was approximately
75 meters by 20 meters at the beginning of the study.
itertidally, as well as sub-tidally, thes rocks provide
agood ase for
ny species of Rhodophyta, Phaeophyta.
surf grass (principally P
hyllo
x), and a few species
of Chlorophyta. Offshore, to the north and south of the
cove, there are large kelp beds (Pearse, et. al., 1971).
consisting principally of Macro
stis pyrifera, Cy
oseira
osmundacea, and Dictyoneu
is reticulata (Pearse, et. al.,
1971). Winds, when present, prevail from the north west to
the east. The
ncurrente
feting the depos
tion of
drift on the beach is no
th-south,resulti
ng in the major
of drift and sand being lef
ton the southern portion of
the beach, Gmith, 1968) (Figures 2,3).
AREA
II
II
+
TABLE 1. Initial Measurements

DTS
INITIAL TIDAL RISE IN
20 FT.

3.6'-5.0
3.3'-5.0
3.6'-7.1
INITIAL
SLOPE
.07
.08
se
Takle 1.
Elaine Evans
Methods and Materials
To estimate the changes in quantity of drift on the
beach a photographic method was employed. Two pictures.
a north view and a southe view, were taked each day at the
low tide. Information from these pictures was then trans-
ferred to graph papper, with the aid of a plastic overlay.
which corrected for the foreshortening of the Ploaroid camera.
The overlay grid was made be staking out the beach at 2-meter
itervals from east to west, and photo
phing the beach while
staked out at low tide. C.
tical stakes were left in so that
the picture could be aligned under the overlay each day.
Figures from the dia
ams made from the pictures, as well as
depth measurements made with a meter stick, were used to estimate
the wet volume of the beach each day.
In order to es
mate what the dry weight of the total drift
of each day was, a wet volume/dry weight conversion factor was
determined. Every day a packed 1/4 cubic meter of we drift
would be sampled, wet weighed, dried 24 hours at 60°0, and dry
weighed. This number was then used to make a total beach dry
mate by multiplying the conversion factor times the total
beach wet volume.
Three areas along the beach were selected to measure more
carefully the quantity of drift arriving. Each was twenty feet
long and five feet wide. Area I was furthest south, and area II
lirty feet north of it, with similar exposure. Area III was
located on the northern end of the beach. The table indicates
some initial measurements but these varied over the period, toble
some extent. (Table 1.)
Elaine Evans 6
Each day, at the lowest tide of the day, the north
half of each area was cleared of drift. The sampling was
done by hand as raking accumulates too much sand. Each
area's sample was placed in a marked plastic bag, to be
weighed later. At this time the temperature, wind, wave
heights, and sunlight observations, were made for the day.
Pieces of drift greater than 15 centimeters were removed
from the south half of each marked area, and tagged with
colored, numbered, plastic tape, and replaced on the area.
Every two days the slopes of the marked areas was measured.
The bagged samples were wet weighed using a spring ba-
lance and then subtracting the weight of the tared plastic
bag. The samples were dried in aluminium foil baking dishes
for 24 hours at 60°, and then dry weighed using a spring
balance.
To determine the relative percentage composition, bby
class, of the drift arriving on these areas, prior to
drying each sample was sorted on quadrated paper, into
Rhodophyta, Phaeophyta, Chlorophyta, and surf grasses.
Bulk percentage composition was determined in this way, for
each sample. The Rhodophytes were principally Gigartina
era, and Gigart
californica, while the Phaeo-
corymbi
phytes consisted mainly of Macrocystis. Chlorophytes were
not very prevalent and were comprised of various Ulva.
The surf grass was Phyllospadix
souler
he potential organic m
tter which is deposited on these
areas was es
tablished using a method similar to that one
described by Doty (1967). The modification of the method
Elaine Evans 7
was that a packed volume of .02 cubic meter of each sample
was treated, instead of the whole sample, and this
num¬
ber was used as a factor to estimate the potential
organic
input. This technique was also used to determine a treated
dry weight/dry weight percentage, for each class,
(Figure 9).
Doty's method was selected rather than an ashing
technique
because it allowed treatment of a larger number of samples.
and because of experimental difficulties with the muffle
furnace used in ashing.
Results
1. The photog
graphic study showed that periodically
ties of drift arrive on the beach. The drift
large quan
is distributed nearly equally along the beach except for a
large quantity deposited on the southern end (Fi
jure 2).
2. Removal of some of the drift begins immediately.
Some drift is first moved south (Figure 3), and then is re-
moved from the beach, or is buried, (Figure 4). The beach
is relatively clear again six days later (Figure 5). Old
stis pneumatocystsre
Marocy
main at the top of the beach.
mates were made with a wet
3. The total beach est
volume/dry weight conversion factor which was influenced by
the wave height and tidal level of the day. After the
repeated depositions of drift on the beach the high waters
remove it gradually; decreasing tides fail to return as
oved (F:
igure 6). The average estimated
much drift as is
inse
fige
150
(
n
Pgu
Elaine Evans 8
dry weight per day was.343 kilograms per square meter.
4. The greater the difference between the preceding
high tide and the low tide of the sampling time (tidal out¬
sweep), the less dry weight of drift present on the beach
(Figure 7).
5. Specific areas I, II, III, had dry weight
increases when there was an increase in the total amount of
drift on the beach, (Figure 8).
6. Percentage treated organic dry weight over total
dry weight was determined for each class, for twenty samples
of each class, (95% significant) (Figure 9). T
These figures
indicate that carbonates and other solubles removed by acid
treatment used to determined "Treated organic dry weigh
are less commonly found on brown algae, Phyllospadix, red
reen algae, in that order. Except for days
algae, and
following increased wave action, the proportions of plants
making up the drift are also in this order. In a 24 hour
drying period greatest weight loss from loss of water was
seen in brown algae.
gging experiments yielded approximately 15-20%
70
reat to make
return, but the sampling error is really too
gnificant generalizations about the residence time of
tions on the beach and in the shallow sub-tidal.
drift depos
8. Relative percentage composition by bulk of each
class, and the ratio of treated organic dry weight to dry
Relative proportions
weight was determined for each sample.
of surf grasses and Rhodophytes increase on days following
heavy wave action, (Figure 10) such as May 1, May 9, and
fque 10

Elaine Evans
May
20.
9. The dry weights and slopes for two similar areas
on the beach were compared (Figure 11). The greater the
slope of a beach area, the lesser the drift remaining.
Disoussion
There are both rhythmic and causal factors involved
in the total quantity of drift on the beach. The causal
factor is a large deposition of drift on the beach, (Figure
6) which appears to be the result of wind waves the day pre-
vious to the deposition. The increased wave action is re-
moving algae and grasses from the sub-tidal and inter-
tidal regions of the cove. The greater the tidal out-sweep.
the less drift left on the beach, (Figure 7). A longer study
would be necessary to defi
nitely determine this but the
3m
prelimi
y data indicate this trend.
The rhythmic factor enters into the results in the
form of the high water level preceding the sampling. As
the tides decrease so does the total dry weight of the drift
on the beach. Thisp
pattern is observed on the total beach
(Figure 6) following each large deposition of dris
ft, and
is also demonstrated in the specific three areas, (Figure 8).
In the specific areas, however, there would appear to be some
m
exceptions to this but upon closer examil
nation these occur
when the tide and waves are high enough to wash up over the
area, depositing drift above the marked areas as on May 14,
Elaine Evans 10
or when the high water level is not high enough to have
reached the marked areas since the last sampling, as on
May 4, 5. 6, 7, and 8, in area III, and May 21, 22, 23, on
all areas.
The wind waves are also affecting the class composi-
tion by bulk, with a marked increase in relative amounts of
Rhodophyta and surf grass the day following stronger wave
action. They are being torn from the rocks in the cove by
the higher ene
y wave action, (Figure 10). It would be
difficult to make any further generalizations about the
make up of the drift due to sampling error.
The potential organic contribution results (Figure 9)
show that certain classes of drift contain more organic
matter than others. However the fact that the ratio of
treated dry organic ma
tter to dry weightr
ns fairly
constant, varying only.07 would indicate that the composi¬
tion of the drift does not fluctuate enough to drastically
ffect the potential organic input, over the period studied.
What does fluctuate, of course, is the total quar
ity of
drift on the beach, and this must have the greatest impact
on the organisms living there. Although the figures for
organic matter tell us something, they do not indicate the
organic contribution being made directly to the beach.
In order to dete:
ne this one would have to consider the
ten per cent of the dri
t which remains long enough to be
he relative rates of
broken down completely, as well as
razing
decay of various classes due to bacterial decay and,
by larger organisms.
Elaine Evans 11
In areas I, II, III, the same relationships were obser¬
ved with respect to wave action and high water level, as were
made for the total beach. Since areas I and II are on simi¬
lar locations on the beach, the consistently lower figures
for area I may be interpreted as a result of I's greater
slope. As change in slope is related to wind and wave action,
as well as high water level, its pattern of flux is often paral¬
lel to that of the drift. The graphs of these two similar
areas however, indicate to me that the greater the slope,
the lesser the amount of drift remaining (Figure 11).
Summary
Increased wave action is the principal cause of arrivals
of large quantities of drift on the sandy beach. As the high
water level decreases so does the amount of drift left on the
beach. Composition of drift on the total beach area is
difficult to assess; it was observed however, that the
asses were larger following
quantities of Rhodophytes and surf
a period of increased wave action. Thus what arrives on the
beach is also related to wind and water movements. Compo-
tion of the dri
t appears constant enough and sufficently
airly uniform percentage of organic matter
mixed to yield a:
potentially available, although some portions of the dri
such as Phaeophytes may contribute more organic material
àn other groups. Quantity available and rate of decay fluc-
tuate greatly, however, and appear to be lim
greal con¬
tribution. The slope of the beach changes because of shifting
sand, itself a result of wind wave action and high water level
Elaine Ev
and in turn slope also affects the amount of drift depe
and remaining on the beach.
Figure
Figure
Figure
Figure
Figure
Figure
Figure
gure
Figure
Figure
Figure
Captions
April 26, start of project.
May 1, a large deposition of drift arrives.
May 3, removal of some drift; larger quantities
moved to southern end of beach.
May 10, drift at the south end is being buried
and removed.
May 16, beach is clear again of major piles of
drift.
otal beach dry weight estimates were made using
a wet volume/dry weight conversion factor. Conver-
sion factor was made for each day as it was de-
pendent upon wave height and tidal level.
-
Specific areas I,I,lil, had dry weight increases
concurrent with the total amount of drift on the
beach.
tage treated organic matter dry
es fo ee
weight, over total dry weight, by class.
Relative percentage composition by bulk of each
he ratio of treated organic matter
class, andt
dry weight to dry weight.
10. This
figure shows that the greater the slope of
a beach area, the lesser the drift deposited and
emaining.
t on the beach is inversely
ropor¬
11. Amount of dri
tional to the tidal out-sweep.
1.
Literature Cited
rovement and application of
Doty, M. S. 1967. Im
benthic algal isotope productivi
measuring
methods. Uni. of Hawaii Bot. Sci. Paper No. 3:
G-1 - G-99.
Pearse, J. S., et. al. 1971. A Kelp bed as a
room resultsof a -weekl
study of!
kelp

beds in Mont
ey Bay
ion. Hopkins Marine
tion, Pacific Grove, Calif., pp. 19-32.
nith, L. K. 1968. The role of benthic
marine plants
in the littoral phosphate cycle. Ph.D. thesis,
Stanford University, on file at Hopkins Marine.
Station, pp. 243-249.
ZoBell, C. E. 1971. Drift Seaweeds on San Diego
County beaches, in W. North, Ed., The biology of
Giant Kelp Beds (Macrocys
is).E
eihef
te zur Nova
Hadwigia 32: 269-314.
Acknowled
would like to thank Dr. Isabella Abbott for
help, advice, and encouragement.
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
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