Abst:
Phytoplankton productivity, standing crop, and community
composition were investigated along a 15 km transect in Monterey
Bay from deep water to the extreme nearshore (30m from beach)
during a five week study in April and May, 1972. Consistent
and significant decreases in productivity and standing crop were
observed at the extreme nearshore station as compared to a station
200m offshore. Community structure remained relatively stable
during the period of study. Several hypotheses are offered in
an attempt to explain the observed nearshore decrease.
Introduction
The relationship between oceanic and neritic phytoplankton
production and standing crop has been investigated along the West
Coast of North America (Anderson, 1964, Curl and Small, 1965, and
Malone, 1971) and the long term cycle of phytoplankton occurance
within Monterey Bay has been described by Bolin and Abbott (1961).
Little work has been done, however, on the productivity and stand-
ing crop in extreme nearshore areas, i.e., less than 1000 meters
from shore.
The phytoplankton of the Monterey Bay are subjected to chang-
ing hydrographic conditions at different times of the year, and
these have been characterized by Bolin and Abbott (1961). The
period of upwelling normally begins in February or March as a re-
sult of the prevailing N to NW winds. The winds parallel the coast.
and under the influence of Coreolis force cause an offshore move-
ment of the surface waters. These are replaced by a vertical move-
ment of colder, nutrient rich water from depths of 300-500m. As a
result, the upwelling period is characterized by low surface tempe-
ratures (9.5 to 11.5), high salinities (33.2% to 33.98), and high
nutrient levels (22.0 uM POh-P, 95.0 uM NO,-N, and,10.0 uM SiOa-Si).
These upwelling conditions were present throughout the period of
investigation.
The present study was designed to document the relationships
between primary productivity, standing crop, and community compo-
sition in the Monterey Bay phytoplankton communities along a 15 km
transect reaching from deep water (depth 900m) to the extreme
nearshore (depth 10m).
Methods
Measurements of primary productivity and standing crop
were made at four stations in Monterey Bay over a five week
period from April 20 to May 16, 1972. The positions of the four
stations are shown in Figures 1 and 2. The deep water station.
CalcOFI 3, is located over the Monterey Submarine Canyon in
about 900 meters of water; CalcOFI 1, the bell buoy adjacent to
Hopkins Marine Station, is in about 40 meters of water; and the
two nearshore stations are located in the lee of Cabrillo Point.
one at the fish hopper, about 200 meters off the beach, and the
other in the area between the rocks flanking the Agassiz back
beach cove of the Marine Station, about 30 meters offshore.
The water depths at the Hopper and Nearshore are 20 meters and
10 meters, respectively.
Water samples were collected in polyethylene bottles from
a skiff at the two nearshore stations from  meter depths.
Samples at CalcOFI 1 and CalcOFI 3 were collected from 0, 5.
15, and 30 meter depths in Van Dorn bottles (Van Dorn, 1956)
during weekly cruises. All samples were collected prior to
1000 PST. Two light bottles and one dark bottle were drawn
from each sample, inoculated with Naplco3, and incubated under
flourescent light (about 0.06 langley/min) for 3 hours at sea-
surface temperature (Doty and Oguri, 1958). Following incuba-
tion, the bottles were filtered through .45 micron Millapore
HA filters. The filters were then rinsed with about 15 ml of
filtered sea water, dried in a dessicator, then counted on a
Nuclear Chicago scalar (model 161A) equipped with a model D47
gas flow chambor with a micromil window. Rates of carbon
fixetion were calculated after averaging duplicate light
bottle values. Mean coefficient of variation between duplicate
light bottles was 8.7+2.0 (95% confidence limits). The method
of 140 labeling has been shown to be a dependable tool for
determining relative rates of photosynthesis in marine phyto-
plankton (Doty and Oguri, 1958).
Samples for chlorophyll analysis were also drawn from the
water samples, and chlorophyll, and phaeopigment concentrations
were found using the flourometic method of Strickland and Parsons
(1968). Samples were fractionated into netplankton and nanno-
plankton size classes by passing one of two replicates through
a 20 micron net filter prior to filtration thorugh a Whatman
GF/C glass filter. The other replicate was filtered directly
through the GF/C filter. Two ml of a 1 MgCo3 solution was
used to coat the filters.
The flourometric technique gives a measure of chlorophyll,
present in any given water sample, and gives good comparative
standing crop estimates as long as the species compositon remains
relatively stable between stations. While standing crop values,
using chlorophyllg as an index, may give a mistaken impression
of the absolute standing crop (different phytoplankters may
contain varying amounts of chlorophyll per unit volume), they
are still a valuable index of standing crop between sampling
stations, particularly during a period which shows no major
changes in phytoplankton community composition.
Direct cell count was also used as a measure of the standing
crop of netplankton (» 20 microns) and to provide data for deter-
mining community composition. Preserved samples of 100 ml were
placed in Nessler tubes and allowed to settle for 24 hours.
Ninety ml were then drawn off with an aspirator, and a 2 ml
aliquot was counted under an inverted microscope using the tech-
nique of Untermöhl (Lund, et al, 1958). The technique proved
adequate ( +
5%) for those phytoplankton larger than 20 microns,
but the fractionated chlorophylla values indicate that a sig-
nificant amount of nannoplankton was overlooked in the direct
counts.
Results
The levels of primary production and standing crop along
the study transect for each cruise are presented in Figures 3-7.
During the entire study, the standing crop and productivity in-
creased from deep water to CalcOFI 1, and decreased inshore of
CalcOFI 1. In addition, the data on corresponding cell density
supported the difference in standing crop between the nearshore
stations. Figure 8 presents the numbers of cell per liter at
each station for each week of the study. Although some of the
differences in cell numbers between the Hopper and Nearshore
are small, the percent contribution to each sample by the nanno-
plankton has been underestimated by direct count. Addition of
the total nannoplankton fraction would make the cell count results
a more significant index of the total standing crop.
The general increase in productivity from week to week is
shown in Figure 9. This graph also illustrates the consistent
drop in productivity between the Hopper and Nearshore, and in
some cases, between CalcOFI 1 and the Hopper.
Pulses within an upwelling period are often observed, and
the standing crop data shown in Figure 10 illustrates the dif-
ferent responses of the inshore stations to a strong upwelling
pulse on May 9. Nearshore is located inshore of a large Macro-
stis bed, while Hopper is located slightly offshore of the
same bed. The presence of the kelp bed may help create differ-
ent inshore environments for phytoplankton within short distances.
The differences in density of cells between the Hopper and
Nearshore can also be illustrated by calculation of the biomass
at each station as shown in Figure 11. These biomass figures
revresent averages of fractionated chlorophyll, data for the
whole study multiplied by a conversion factor to determine
biomass (Strickland and Parsons, 1968).
The vertical distribution of the standing crop refiects the
changing conditions which can occur within a period of general up-
welling and nutrient rich waters. This is presented graphically
in Figures 12-16.
The analysis of the phytoplankton community composition is pre-
sented in Tables 1-3. The composition of the community at any one
station changed only slightly during the five week study, and none
of the observed differences indicated a major shift in the types of
phytoplankters present. In general, the community present at
CalcorI 1, Hopper, and Nearshore on any one day was relatively
uniform, as expressed by genera present and percentage component
of the total community. The decrease in cell numbers on May 16
reflects the tailing off of the spring bloom in the Monterey Bay,
Discussion
The significant decrease in primary production, with the
accompanying decreases in standing crop and direct cell counts
over the period of study indicate that extreme nearshore phyto¬
plankton populations are exposed to conditions not normally
encountered by pelagic diatoms. The statistical significance
of the productivity decrease is P-.06; considering that two
additional parameters are also exhibiting the same trend, the
results become quite striking.
A complex system of hydrographic and biological factors
is operating in the shallower nearshore waters, possibly
providing different environmental conditions within a very
narrow spatial framework. Phytoplankton standing crop in the
open ocean is limited primarily by grazing of zooplankton and
limiting nutrient levels due to stratified water columns. It
is possible that zooplankton grazing is reducing the phytoplankton
population in extreme nearshore areas, however, the depth of
the water column at the inshore stations makes this a remote
possibility, since much of the zooplankton biomass need deeper
water for daily vertical migration.
Table 4 presents the ratio of phaeophytin to chlorophylla
for the five weeks of the study. The nearshore area consistent-
ly showed an increase in phaeophytin with respect to chlorophyll.
This ratio is often used as an index of grazing pressure on
phytoplankton, extreme nearshore areas, however, are affected
by many other factors creating phaeophytin, and grazing may
quantitatively be the least important.
One factor which could influence the productivity and
standing crop is the breakdown of the phytoplankton as a result
of physical contact with the rocky shore, the shallow bottom,
or the sandy beach. The increase in the ratio of phaeophytin
to chlorophyll, could be the result of cell damage followed by
bleaching. Yentsch (1970) has suggested this as the principal
mechanism of chlorophyll degradation following cell fracture.
The physical breakdown of cells could account for some portion
of the reduction in standing crop and productivity. However,
the increase in phaeopigments in the shallow water could also
be a result of increasing contributions of benthic algal detritus
and wastes from intertidal animals. The digested food products
of a large filter-feeding population could contribute signif-
icantly to levels of phaeophytin, either by those animals in
the immediate area or perhaps by animals "upstream" of the study
area.
The presence of benthic algae in the shallower water may
also influence the productivity and standing crop of a phyto-
plankton population. A comparison of phytoplankton biomass
with that of the benthic algae illustrates the enormous amount
of benthic material present in the immediate vicinity of the
study area. Blinks (1955) gives the total biomass of nine major
benthic algae as 15 kg/m, while the biomass of phytoplankton
may reach 500 mg/m2 only under peak bloom conditions. Ryther
and Kramer (1961) demonstrated that an inshore species, Skele-
tonema costatum, requires 10 to 20 times the amount of minor
nutrients, e.g. iron, as offshore species. Recent work by
Lewin and Chen (1971) also indicates that inshore diatoms are
not as efficient in utilizing available iron. If the benthic
algae are either using or concentrating minor nutrients, the
inshore populations of diatoms could be suffering a nutrient
deficiency and not turning over as fast as under normal nutrient
conditions.
It can also be speculated that bacterial activity could
increase as a phytoplankton population moves to shallower water.
The presence of benthic algae, increasing waste products from
intertidal and bentic animals, and increasing amounts of detritus
could all lead to a larger bacterial population in the nearshore
waters. How these bacteria might affect the photosynthetic
efficiency or the productivity of a cell is open to speculation.
The most attractive hypothesis to explain decreased prod-
uctivity and standing crop nearshore is that of photodegradation
of chlorophyll. The growth inhibition of diatoms in response to
high light conditions has been noted by Epel and Krauss (1966).
The role of chlorophyllase in chlorophyll degradation is a
source of controversy at present (Yentsch and Moreth, 1970.
Barrett and Jefferies, 1971), but there is the possibility that
the bleaching of cells due to higher mean light levels in
shallow water activates the membrane-bound chlorophyllas to
degrade the chlorophyll to phaeophytin within the living cell.
Conversely, under certain conditions photodegradation could
be minimized in a community which had moved inshore as the top
10 meters of a highly stratified water column. The ability of
a high-density population to shade itself and thereby lower the
10
depth of the mean light intensity could prevent photoinactivation
as the community moves into shallower water. Stratification
wheih occurred at CalcOFI 1 on May 15 is a good illustration of
this. Figure 17 presents the vertical density layers, showing
the thin layer of low density water from O to 5 meters in depth.
In order to make any generalizations about the relative
production rates at nearshore stations it will be necessary to
compile information throughout the annual cycle of hydrog:
raphic
conditions in the Monterey Bay. Phytoplankton populations could
fferent relationships between deep and shallow
possibly show d
water stations as the community composition changes during the
year. The absolut values of productivity and standing crop would
surely change but the relative values should stay the same.
Some variation in productivity and standing crop may be a
result of "patohes" or bands of phytoplankton, formed by local
current systems. Aerial photographs taken over Monterey Bay
during the fall season have shown bands of high chlorophyll
concentrations in the surface waters. However, this is considered
to be much more likely during the stratified conditions occurring
in the autumn months than during the period of study.
imma
1) A significant decrease in productivity and standing crop
was observed between inshore stations which were 30 m. 200 m.
and 600 m from the shore, respectively, with the largest and
most significant change occurring from 30 meters to 200 meters
offshore.
11
2) Community composition during the study changed slightly
from week to weck, but no significant changes occured between
inshore stations on any one day.
3) Several possible explanations are offered, including
effects of physical breakdown, bacterial activity, nutrient
deficiency, photoinactivation of chlorophyll, and feeding by
benthic and intertidal animals.
Acknowledgements
I would like to thank Dr. Malvern Gilmartin for providing
ship time aboard the RV Proteus, and for his timely advice and
guidance throughout this study. I would also like to thank
Dr. Isabella A. Abbott for her patience and good humor while
assisting with phytoplankton identification. Thanks also to
Peter Davoll and Ken Johnson for providing hydrographic data
for CalcOFI 1 and CalcOFI 3.
Reference
Anderson, G. C. 1964. The seasonal and geographic distribution
of primary productivity off the Washington and Oregon coasts.
Limnol. Oceanogr. 9: 284-302.
Barrett, J., and S. W. Jeffereys. 1971. A note on the occurrence
of chlorophyllase in marine algae. J. exp mar. Biol. Ecol.
7: 255-262.
Blinks, L. R. 1955. Photosynthesis and productivity of littoral
marine algae.
Bolin, R. L., and D. P. Abbott. 1961. Studies on the marine
climate and phytoplankton of the central coastal area of
California, 1954-1960. Calif. Coop. Oceanic Fish. Invest.,
Rep. 9: 23-15.
Curl,
H., and L. F. Small. 1965. Variations in photosynthetic
assimilation ratios'in natural marine phytoplankton comm-
unities. Limnol. Oceanogr. 10 (Suppl.): R67-R73.
Doty, M. S., and M. Oguri. 1958. Selected features of the
isotopic carbon primary productivity technique. Rapp.
Proc. Verb., Cons. Int. Explor. Mer 144: 47-55.
Epel,
B., and R. W. Krauss. 1966. The inhibitor effect of
light on growth of Prototheca zopfii. Biochim. biophys.
ACTA 120: 73-83.
Lewin, J., and C. Chen. 1971. Available iron: a limiting
factor for marine phytoplankton. Limnol. Oceanogr. 16:
670-674.
Lund, J. W. G., C. Kipling, and E. D. Lecren.
1958. The inverted
microscope method of estimatin algal numbers and the stat-
tical basis of estimation of counting. Hydrobiologia 11:
143-170.
Malone, T. C. 1971. The relative importance of nannoplankton
and netplankton as primary producers in the California
Current System. Fish. Bull. 69: 799-820.
Ryther, J. H., and D. D. Kramer. 1961. Relative iron requirement
of some coastal and offshore plankton algae. Ecology 42:
LLL-16.
Strickland, J. D. H., and T. R. Parsons. 1968. A practical
hankbook of seawater analysis. Bull. Fish. Res. Bd. Can.
167. 311 p.
Van Dorn, W. G. 1956. Large volume water sampler. Trans. Am.
geophys. Un. 37: 6.
Yentsch, C. S., and Moreth, C. M. 1970., The role of chloro¬
yyllase and light in the decomposition of chlorophyll
rom marine phytoplankton. J. exp. mar. Biol. Ecol.
4: 238-249.
0



• CalCOFI 3


GOICOFI

FEIGURE
FIGUR!

C

C
CalCOFIQ
HOPPER E
* NEARSHORE



HOPRINS MARINE
STATION
O

meters
3000
CPM
2000
o00

....



CPM
3o00
2000
000

CPM
3000
2000
000
FIGURE
cC-3


EIGURE 5
cc-3
FIGURE

cc-5
20 APR
—
1
CC-I HOPPER NEAR
SHORE
2 MAY

CC- HOPPER NEAR
SHORE
16 MAY

CC-I HOPPER NERR
SHORE

25 APR
FIGURE 4
3000
machl
CPM
4
2 m3
2000
100
CC-3
CC-I HOPPER NEAR
SHORE

9 MAY
FIGURE
CPM
mo Chl
3

3 m3
3000

2000

—000


—
cc-3Cc HOPPER NEAR

SHORE
4--+ PRODUCTIVITY

mg Ch
3-m3—
STANDING CROP

2




mch
2 m3
maChl
3 m
+
+

—

I


ena



o


Ta.


poo



A
n

13




2
——

.  n

DO
...
e

7
ni.

.
.
DO




po
m
T2-
.

.

O
—

2


E.

m


n
tääaansantin
0





8
O

r.k.. FL

H

t






—
k tat






t
—
poooooo


-



t
E


p
ad




O



k
......
...:
O

.....
oooo
7 7—


ID


i
m

ET
N

O

l
1







—


M

8



8


+




















S



.... ..

I














1


6

C
X
1


—


+



E


â€






-
1   —
1


I

I

1
N
0




0
————






N






.
—




100

—+

mqc
me
60
40


20


—
.








—



L





EIGURE 11





HOPPER
E
I

1








LLE  E


MAL
+ +

mmii
+






i








I



++

.



SIZE CLASSES


820 microns






20 microns


—




NEARSHORE
2
L
1



0

E

11



El
OE
10


10
o.
L

E

L



520

8
4
089 8
—

L



0




+


M




—

8
9
8




28 K 8
S
C



—



1








+
u


1.— 1



1

58
oL
O
—


E
8 8
5
.




28 8
5


L




ir


+



8





:.
+






-
GE
Rhizoselenia
Chaetoseros
Eucampia
zschia
Skeletonema
Navicula
Ditylum
Thalasionema
Thalasiosira
Cosoinodisous
Licmorpha
Asterionella
Stephanopyxis
Biddulphia
Lauderia
Noctiluca
other Dinoflag.
+20 microns
unidentified
20 April
172000
78500
2700
10200
3800
540
360
900
540
180
180
180
Table 1
5 April
86000
164000
10500
2500
8180
360
900
11300
1440
20300
2 May
265000
120000
10400
6900
2540
180
180
2000
3220
1620
1080
1080
1080
9 May
330000
192000
3820
16000
62700
180
1270
360
2550
720
1450
1810
540
7640
16 May
3000
4500
720
1080
360
180
2700
1080
ENUS
Rhizoselenia
Chaetoseros
Eucampia
itzschia
Skeletonema
Navicula
Ditylum
Thalassionema
Thalasiosira
osindisous
Licmorpha
Noctiluca
other Dinoflag.
Asterionella
Silicaflag.
Biddulphia
20 microns
unidentified
20 AD
136000
152000
19300
8180
1910
180
900
540
180
180
900
1750
Table 2
April
May
78200
215000
230000
119000
38200
8180
7600
11300
17800
3040
360
360
1080
2180
180
1350
1440
720
13690
11300
360
360
10200
9 M-
338000
235000
loo0
16400
28500
360
2180
720
540
12200
2730
180
4360
16 May
5850
151000
1780
11200
16000
500
1080
750
GENUS
lhizoselenia
Chaetoseros
Eucampia
Nitzschia
Skeletonema
Navicula
sterionella
Thalassionema
Thalassiosira
osinodisous
Stephanopyxis
Lauderia
Bacteriastrum
Noctiluca
other Dinoflag.
Silicaflag.
20 microns
unidentified
20 April
74700
170000
17300
19100
37600
9640
1o00
180
3090
360
3450
360
5090
540
1080
Table 3
25 April
2M
182000
179000
17800
27100
16400
720
2550
1080
720
3820
540
7090
91
290000
114000
8550
6730
14700
24900
1800
1700
360
3090
360
180
8910
1800
13100
16 Ma
53100
90200
o00
12200
63600
180
360
360
5400
540
3270
360
12000
Nearshore
Hopper
Calco
I Om
5m
15m
30m
CalcOFI
Om
5m
15m
3Om
20 April
.66
47
.16
.43
.55
1.
.26
.57
1.60
Table 1
5 April
.90
.16
.12
.11
1.08
.01
.17
.13
50
Ul
.08
.1
.02
1.30
.15
.08
.20
1.43
9 May
.08
.09
.09
.17
.25
.61
.18
.49
53
1.25
16 May
2.29
.20
.41
.10
.4
.36
.56
.51
.55
.51
gure Legend
Figure 1. The locations of CalcOFI 3 and CalcOFI 1 with respect to
Monterey Bay.
Figure 2. The positions of the inshore stations with respect to
Hopkins Marine Station.
Figure 3-7. Comparisons of productivity and standing crop at the four
stations.
Figure 8. Comparison of direct cell counts between the three inshore
stations.
Figure 9. Comparison of productivity between all stations during the
study.
Figure 10. Standing crop at the inshore stations during the five
weeks of the study.
Figure 11. Comparison of biomass between the nearshore stations with
size class breakdown.
Figure 12-16. Vertical distribution of chlorophylla at CalcOFI 1
during the five weeks of the study.
Figure 17. Vertical density layers at CalcOFI 1.
0
e
e
able Legends
Table 1. Community composition at Nearshore.
Table 2. Community composition at Hopper.
Table 3. Community composition at CalcOFI 1, surface only.
Table 4. Ration of phaeopigment to chlorophyll, at all stations.