Download on circulation, phosphate-phosphorus content, and zooplankton

ON CIRCULATION,
PHOSPHATE-PHOSPHORUS
CONTENT,
AND ZOOPLANKTON
VOLUMES IN THE UPPER PART
OF THE PACIFIC OCEAN’
Joseph L. Reid, Jr.
Scripps Institution
of Oceanography
ABSTRACT
The circulation
of the Pacific Ocean may bc considcrcd to consist of two high-latitude
cyclonic gyres, two subtropical
anticyclonic
gyres, and a series of subequatorial
zonal flows
in alternate directions.
The phosphate-phosphorus
at the surface is related to the surface
divcrgcnce
and is high in the cyclones, low in the anticycloncs,
and high in regions of
coastal and equatorial
upwelling.
The POa-P at 100 m is related to the depth of the
pycnocline
and is also high in the cyclones and low in the anticyclones,
and high at the
equator and at the poleward
edges of the equatorial
countercurrents.
The zooplankton
volume is distributed
very much as is the P&P,
particularly
that at 100 m. It is also low
in the anticyclones
<and high in the cyclones, at the equator and at the poleward edges of
the equatorial countercurrents.
At the center of the subarctic cyclone, however, zooplankton
is only moderate, but Pod-P concentration
is high both at the surface and at 100 m. It is
suggested that the surface divergence
is too rapid for zooplankton
to accumulate
in the
center of the cyclone, even though reproduction
and growth may be prolific.
In the California
Current zooplankton
volume appears to vary inversely with temperature,
is found near the tip of Baja
an d an area of minimum volume and maximum temperature
California.
It is speculated that this indicates a change from subarctic to subequatorial
species. This, and the close relation of the plankton volume to the system of gyres, suggests
that the gyres may rcprcscnt the principal plankton communities.
INTRODUCTION
An interesting correspondence may be
noted between the maps of circulation, inorganic phosphate-phosphorus
content in
the upper levels, and zooplankton volume
that appear in the NORPAC
ATLAS
(NORPAC Committee 1960). In extending
the map of circulation to cover the rest of
the Pacific ( Reid 1961)) it was found that
there were enough available data to extend
the other maps also. CoXrrespondcnce between the three quantities is then found
over the entire Pacific.
There are theories of the nature of ocean
circulation that can account for the distribution of the P04-P. If correct, they must
also be consonant with the observed distribution of zoopkankton volumes, and it is interesting to speculate fro,m the point of
view of physical oceanography alone about
the nature of the plankton communities,
THE
CIRCULATION
The currents
With certain limitations, the geopotential
anomaly at the sea surface with respect to
the l,OOO-dccibar surface (Fig. 1 reproduced from Reid 1961) represents the surface currents and may be used to illustrate
the features of the circulation that are discussed here. Since only the geostrophic
flow is represented in the figure, the current field is incomplete, and one must
imagine enough cross-contour flow to avoid
over-running the continents and to balance
the apparent convergence at the equator.
The two major features are the two huge
subtropical anticyclones which include the
western bo,undary currents, parts of the
l This work was supported by the Marine Lift
west
wind drift, the eastern boundary curResearch Program, the Scripps Institution
of Occarents, and the two westward-flowing
equanography’s
component of the California
Coopcrative Oceanic
Fisheries
Investigations,
a project
torial currents a few degrees north and
sponsored by the Marine Research Committee
of
south oI the equator. At higher latitudes,
the State of California.
I am particularly
grateful
there are the Antarctic Circumpolar Curto Mr Garth Murphy
of the California
Academy
rent and the system containing the Alaska
of Scicnccs for many helpful discussions and comments and for reading the manuscript,
Current and the Oyashio Current. Both of
287
288
JOSEPH
L.
REID,
JR.
FIG. 1. Currents at the surface of the Pacific Ocean (gcopotential
respect to the l,OOO-decibar surface, in dynamic meters ) .
these systems are cyclonic (with the South
Pole at the center of the southern one) and
will be referred to, respectively, as the subantarctic and the subarctic cyclones.
Equatorward
of the subtropical anticyclones, the flow is zonal except at the eastcm and western boundaries. The flow is
westward at the equator with countercurrents north and south of the equator. The
southern coun tcrcurrent is better developed
in the west and the northern better developcd in the east, somewhat in accordance
anomaly
at the sea surface
with the mean position of the doldrums
either edge of the ocean.
with
at
Divergence and the depth
of the mixed layer
The circulation is wind-driven and partly
balanced geos trophically.
Stommel ( 1957 )
has surveyed the theories of such a system
and prepared schematic illustrations of the
movement. It is seen that within the winddriven anticyclonic
gyres, surface waters
converge and sinking occurs. Within the
CIRCULATION,
TABLE
----
1.
PO4-P,
AND
The inorganic
ZOOPLANKTON
phosphate-phosphorus
--
--~~
-~~~
Vessel or cruise
Period
Aug. 1957-Jan. 1958
July 1950, Sept. 1950
Oct. 1928-Nov. 1929
Aug. 1934
JunoAug. 1956
Nov. 1928-Aug. 1929
May-Oct. 1932, Jan.-Feb.
1936, Jan.-Mar. 1938,
Oct. 1950-June 1951
Downwind
Oct. 1957-Feb. 1958
EASTROPIC Horizon
Oct.-Dee. 1955
Hugh M. Smith Sept.-Dec. 1955
II
Spencer F. Baird Oct.-Dec. 1955
Aug.-Sept. 1956
EQUibAC Hugh M. Smith
II
Or&m III
S&.-Oct. 1956
II
Satsuma
July-Aug. 1956
Albatross
C.C.O.F.I.
Carnegie
Chelan ( USCGS )
Chinook
Dana
Discovery
II
Shunkotsu
May-June 1956
II
II
Stranger
Umitaka
Aug. 1956
Oct.-Nov. 1956
Gannet ( USS )
Hugh M. Smith Cruise 5
,I 38
Muklui’
NORPAC Brown Bear
,,
C.C.O.F.I.
II
Ryofu
II
Satsuma
11
Shiny0
11
Shumpu
II
Ste. Therese
Aug. 1933
July-Aug. 1950
.-Mar. 1957
;;y-Aug.
1957
+June-Oct. 1955
( HMCS )
I,
Tenyo
Umitaka
Yushio
II
OB ;‘955-1956
OB Cruise 3
April-May 1956
May-June 1958
Orsom III 56-5
Orsom III Astrolabc
Oshoro
Queenborough & Quickmatch
William Scoresby
TRANSPAC
Umitaka ( Coral Sea )
Oct. Nov. 1956
May 1958
July+ug. 1956
March-April 1958
May-Aug. 1931
April-June 1958
May-Aug. 1952
July-Nov. 1953
Jan. 1959
Vityax 25
July-Oct. 1957
Vityax 26
Vityax 27
Warreen
Nov. 1957-Feb. 1958
March-June 1958
May-Sept. 1948
Scot
Shellback
--_
Total
- --
IN
THE
materials
-.
No. of stations used
Om
1OOm
51
35
121
3
4:
146
289
PACIFIC
Refcrcnco
52 Bruncau, Jcrlov, and Koczy (1953)
35 Univ. Calif. ( 1955)
121 Fleming and others ( 1945 )
3 Barnes and Thompson ( 1938 )
Unpublished Univ. Calif. data
4: Carlsbcrg Foundation ( 1937)
148 Disc. Comm. ( 1941,1944,1947,
1957)
24 Unpublished Univ. Calif. data
68
18 King, Austin, ani Do;’ ( 19;; )
17 Unpublished Univ. Calif. data
62 Austin (1957)
19 Legand ( 1957 )
17 Unpublished Japanese Hydrographic Office data report
21
27 Unpublished Japanese Fishcries
Agency of Japan data
37
40 Unpublished Univ. Calif. data
16
16 Unpublished Tokyo University of
Fisheries data
4
4 Barnes and Thompson ( 1938 )
14
14 Cromwell and Austin (1954)
42
43 Wilson and Rinkel ( 1957 )
3
3 Unpublished Univ. Calif. data
NORPAC Comm. ( 1960a)
s”: 1;:
II
,I
4
4
,I
II
40
I,
,I
4
4
II
‘1
I,
II
45
44
24
66
22
16
65
19
-
79
10
57
3
18
27
81
11
58
3
12
28
II
,I
,I
I,
I,
I,
U.S.i.R. Acai: Sci. (1958)
Data made available by World
IGY Data Center A
15
18 Rotschi ( 1958 )
43
43 Rots&i, Angot, and Logand (1959)
35
36 Hokkaido U. Fat. Fish. ( 1957 )
12
12 C.S.I.R.O. (1960)
14
16 Disc. Comm. ( 1949)
59
56 Holmes & Blackburn ( 1960 )
102 102 Unpublished Univ. Calif. data
56
56
13
13 Uniublishcd &S.I.<.O. aid
Tokyo Univ. of Fish. data
82
75 Data made available by World
IGY Data Center A
97
92
11
II
51
53
(1951, ;01. 3)
8
8 c.s.&o.
-1,743 1,826
-____----
--
-.-
290
JOSEPH
L.
cyclonic gyres, surface waters diverge and
upwelling of deeper waters to the surface
occurs. The surface layer is thickest at the
centers of the anticyclones, becoming thinner toward the centers of the cyclones and
the coastal boundaries of the anticyclones.
Although the currents ne,ar the equator
are relatively narrow zonal features and in
some cases flow upwind, they still show this
relation of the depth of the mixed layer to
the circulation, In westward flow the mixed
layer is thickest on the poleward sides of
the currents, and vice versa. This results
in a series of zonal ridges and troughs in
the depth of the mixed layer (Cromwell
1958). The observed distribution of P04-P
in the upper layers of the Pacific is shown
to bc consonant with these concepts and
that of coastal and equatorial wind-induced
upwelling (Reid, Roden, and Wyllie 1958;
Cromwell 1953 ) .
INORGANIC
PHOSPHATE-PHOSPHORUS
Nearly everywhere in the ocean, values
of P04-P are lowest in the mixed layer with
a sharp rise in the pycnocline to a maximum
several hundred meters beneath the surface
and a slight decrease from there to the bottom. Maps of the P04-P have been prepared from the materials listed in Table 1
and appear as Figures 2 and 3.
Phosphate-phosphorus
at the sea surface
Where horizontal divergence occurs at
the surface and regenerated materials are
brought into the mixed layer, the surface
concentration of P04-P may become high.
Where convergence occurs, the deplc ted
surface waters accumulate and surface concentrations may become low.
Bohnecke, Hentschcl, and Wattenberg
( 1930) noted the enrichment of the surface waters within the cyclonic gyre between Greenland and Iceland, and proposed that it is caused by horizontal dithe gyre and upwGd
vergence within
movement of the deeper, nutrient-rich
water.
The distribution of PO*-P at the surface
(Fig. 2) is seen to be consonant with this
REID,
JR.
concept of surface divergence. Concentrations rare low in the anticyclones and high
in the cyclones, the areas of coastal upwelling and at the equator. Coastal upwelling
occurs along the California and Peru Currents as a consequence of the equatorward
winds along these coasts, Downwelling
occurs in part of the Alaska Current where
the wind is poleward along the coast of
Canada, and possibly at the southern tip of
South America when the winds have a poleward component. Along the equator, as a
consequence of the earth’s rotation, the
trade winds drive the northern surface waters northward and the southern surface
waters southward, and upwelling
occurs
( Cromwell
1953). Averaged throughout
the year, Hidaka’s (1958) wind stress calculations show that this effect should be
stronger in the eastern half of the ocean
than in the western half. Certainly the
PO,-P concentration does decrease toward
the west.
Phosphate-phosphorus
at 100 m
Since the concentrations of POa-P are
higher beneath the mixed layer, the variation in depth of the pycnocline over the
ocean affects the distribution of POh-P on
any surface of constant depth near the pycnocline. Where the pycnocline is shallow,
the P04-P at 75 m (for example) is high.
Where it lies deeper than 75 m, the POb-P
at 75 m is low, This effect is to be seen on
any levels from 50 m down at least 200 m.
In Figure 3, the effects of the variations
of depth of pycnocline are quite apparent.
The cyclones and anticyclones seen on the
map of currents are clearly defined over
most of the area as regions of high and low
P04-P, respectively.
In these data, the distribution
between
15” N and 15’S is more irregular, but zones
of high P04-P arc seen at the equator, at
about lOoN, and at about 7”s. These three
zones correspond respectively to the Equatorial Current, to the boundary between the
North Equatorial Current and Countercurrent, and less clearly to the southern boundary of the South Equatorial Countercurrent.
CIRCULATION,
Pod-P,
AND
ZOOPLANKTON
The two maps of Pod-P are similar, although consumption occurs at the surface
and regeneration at 100 m. The major difference occurs in the western subequatorial
region. The processes that enrich the surface in the region between the Tropics arc
more effective in the eastern part, and the
surface concentration decreases to the west.
The westward currents near the equator,
however, continue at least as far as New
Guinea, and in the areas of shallow pycnoCline, which are associated with their equatorward boundaries, the Pod-P at 100 m
remains fairly high.
POSSIDLE
AND
EFFECTS
CIRCULATION
OF PHOSPHATE-PHOSPHORUS
UPON
LIFE
IN THE
OCEAN
Phosphate-phosphorus
When one considers that the concentration of Pod-P in the Pacific is much higher
than in the Atlantic and that the Pacific is
not reported to be more productive, one
wonders why Pod-P is examined at all with
Hentschel and
respect to zooplankton.
Wattenberg (193U) included a map of the
central and southern Atlantic showing PObP distribution
in the upper 50 m that is
quite similar in pattern to the Pacific map,
but the values are lower. The average concentration in the Atlantic appears to be
about half of that in the Pacific.
The reason for selecting Pod-P for analysis is that data are available for the entire
Pacific whereas data on other nutrients are
very scanty. Variations of Pod-P may or
may not be important in themsclvcs. They
may bc important as indicators of variations
of other nutrients, such as nitrate, that are
affected by the same processes, b,ut are not
present in excess.
Circulation
The effect of horizontal
and vertical
movement of the water, beyond its effect
on the nutrients, must be considered. The
volume of the plankton in the ocean probably f‘ar exceeds the combined volume of
the free-swimming and bottom organisms,
The movement of the biomass is mostly a
consequence of the motion of the water
rather than of any swimming effort, and the
IN
THE
PACIFIC
291
distribution
in space of the biomass is
severely limited by the currents. Temperature, which may also limit any particular
organism, varies over the greater part of the
ocean largely with latitude (though there
are notable extensions of cold water equatorward in the eastern boundary currents
and of warm water poleward in the western boundary currents). The gyres are relatively narrow zonal features, and therefore the temperature variation within each
gyre is small compared with the differences
between adjacent gyres.
Each of the gyres also acts in a way to
hold a substantial part of the organisms
within it instead of carrying them to areas
with different properties. Convergence in
the anticyclones helps to balance the outward diffusion, and the subarctic and subantarctic cyclones have substantial continental boundaries on one edge that help
to confine some of the individuals.
It is plausible to expect that these areas
of semi-enclosed circulation and relatively
narrow range of properties
are distinguished also by the planktonic faunas that
inhabit them, Since plankters cannot move
against the currents, they require a system
of currents that will allow them to remain
These
within
a tolerable
environment.
gyres, each of which covers only about 20
to 25 dcgrecs of latitude, may be such
systems.
The cxtrcmc ranges of temperature at a
depth of 50 m in the Pacific arc from about
-1 to 10°C in the subarctic cyclone, from
about 8 to 25°C in the northern subtropical
anticyclone, and from about 19 to 29°C in
the subequatorial system. These extreme
ranges include seasonal variations, It may
not be necessary for an organism inhabiting
a gyre to be able to reproduce throughout
the extreme areal and seasonal range of
temperature, but only to survive it (Damas
1905; Svcrdrup,
Johnson, and Fleming
1942). If reproduction occurs in one season only, then the effective range of tempcrature is reduced, and if it occurs in only
one limb of a gyre the range is reduced
even further.
Damas (1905) has suggested the impor-
292
FIG. 2 (a).
7
.
ana contours.
JOSEPII
Distribution
of Pot-P
L.
at the surface
tance of the cyclonic gyre of the Norwegian
Sea in maintaining
organisms in a fixed
region that in part of the year is favorable
for reproduction.
He speculates that gyral
movement in the ocean may play a principal role in preserving species and in the
creation of a special plankton in particular
areas. Hclland-Hansen and Nansen ( 1909)
have reviewed Damas’ findings in the light
of their work on the physical oceanography
of the area and have conftimed his relation
of certain species to’ the water masses.
Somme ( 1933)) although he disagrees with
particulars of Damas’ findings, accepts in
REID,
JR.
of the Pacific
Ocean
(ppd./L),
station
positions,
principle the concept of maintenance of
plankton population
by systems rotating
in fixed positions, and cites also Baffin Bay,
the Gulf of Maine, and the area off the
Lofoten Islands as areas where rotating
systems could be shown to maintain particular populations.
Sverdrup, Johnson, and Fleming (1942)
concluded that current is one determining
factor (p. 863) “. . . in maintuining an enThey cite not only
demic population.”
oscillating tidal currents and restricted flow
in partially landlocked bays but (p. 864)
‘C
. . . gyrating currents, sometimes circum-
CIHCULATION,
FIG. 2 (b).
Distribution
Pod-P,
AND
ZOOPLANKTON
of PO,-P at the surface
scribing relatively
large areas in hydrographically closed systems of more or less
permanence.” The data at that time limited
the examples to small areas.
ZOOPLANKTON
VOLUME
Since P04-P has been considered as a
plant nutrient, it should be compared with
productivity
or with the standing crop of
phytoplankton.
Unfortunately,
there are
very few measurements of these quantities.
The most readily available data on the
biomass consist of measurements of the
of the Pacific
IN
THE
Ocean
PACIFIC
(,ug-at./L)
293.
shaded by values.
plankton volume collected by nets of relatively large mesh (0.25 to 0.55-mm aperture) from the upper few hundred meters
of the ocean. Nets of this type sample
mostly the larger zooplankton.
A larger
volume of smaller forms may escape the
nets, so that these samples cannot represent
the true biomass but only the volume of
karger forms, The materials are specified
and details of the nets are given in Table 2.
About 1,000 of the samples were taken at
stations where measurements of P04-P
were made also.
294
FIG. 3 (a).
Distribution
positions, and contours.
JOSEPH
L.
of POCP at a depth
It is seen that the methods, equipment,
laboratory techniques, and season of collection have varied. However, 1,365 of the
2,005 samples were collected with the
CCOFI-POFI
net. Of the others, 286 were
collected with the Maruto,ku, modified
Marutoku, or NORPAC nets, that differed
from each other only in length. These 1,651
samples were all from measured quantities
of water and will be referred to as the basic
samples. In Table 3 the samples are divided by area, month, and depth of haul.
( The 51 Dnn.n samples and 65 of the
REID,
JR.
of 100 m in the Pacific
Ocean
( pg-at./L),
station
Vrsom III samples are not classified by
depth in the table.)
North of 20”N, 92.5% of the samples are
from the basic group, and those basic samples collected in July, August, and September in hauls from depths of 150 or 140
m to the surface total 629, or 74.3% of all
samples north of 20”N.
Between 20”N and 20’S, 87.4% of the
samples are from the basic group, but they
are almost equally divided between hauls
from 150 or 140 m to the surface and hauls
from 300 m to the surface. Only 39.8% of
CIRCULATION,
FIG.
1
values.
3 (b).
Distribution
P04-P,
AND
ZOOPLANKTON
of PO,-P at a depth of 100
all samples in this area were taken in July,
August, or September, and the remainder
includes samples from all the rest of the
year.
South of 20’S only 15% of the samples
involved measurements of the amount of
water filtered. Sampling extended throughout the year.
Sampling in the northern of the three
areas seems quite adequate for the preparation of a map, Sampling in the equatorial
region is less satisfactory, but the seasonal
variation may be less important there. South
IN
THE
PACIFIC
m in the Pacific Ocean (pg-z&./L)
2%
shaded by
of 20’S, the sampling is poor but it seems
worthwhile to include what data are available. Flowrneters were not used with the
112 Discovery II N70V net hauls, and
therefore the volumes south of 50’S and
those necar Australia are uncertain. The 51
Dana hauls were not metered and were
horizontal, and their values (in the central
South Pacific and near New Zealand) are
uncertain.
For materials without
flowmeters the standardized value has been obtained by assuming unimpeded passage of
the water through the net. The effect of
296
JOSEPH
-.
Name of net
Mesh
at)e$c
RElD,
JR.
Description of the materials used for the map of zooplankton volume
___--- -~~-.
____
-~- _-
TABLE 2.
--
L.
Mouth
diameter
(cnl)
Lyg;h
m
Open or Flowclosmg meter Shape
~-
T’h”,“,;f
-__
Period
-
~.
~---.
N”zbcr
obscrvations
Dep*
‘rzg;
51
200-O
204
300-O
C.,C.O.F.I.0.55 front 100
5.0 Either
Yes Conical Oblique
P.O.F.I. net 0.25rear
(after
wetting)
Hugh M. Smith, Cruise 5 (King and Dcmond 1953)
June-Aug.
1950
Shellback (unpublished Univ. Calif. data)
May-Aug.
1952
TRANSPAC
(unpublished Univ. Calif. data)
Cnpricorn (unpublished Univ. Calif. data)
Troll
(unpublished
July-Nov. 1953
Dec. 1952Feb. 1953
March-April
1955
Univ. Calif. data)
NORPAC
B.C.F., Honolulu (NORPAC Cornm. 1960a,
1960b )
C.C.O.F.I. (NORPAC Comm. 1960a, 1960b)
EASTROPIC
(unpublished Univ. Calif. data)
King, Austin, and Doty ( 1957)
J;kh
EQUAPAC
Aug.-Sept.
1956
(unpublished
Univ. Calif. data)
Hugh M. Smith, Cruise 38 (Wilson
Downwind
C.C.O.F.I.
data)
(unpublished
Gulf of California
Tethys (unpublished
Total,
Marutoku
C.C.O.F.I.-P.O.F.I.
net 0.33
NORPAC
Univ. Calif. data)
(unpnblishcd
B.C.F. La Jolla
Univ. Calif. data)
Total, Marutoku
NORPAC
0.239
ClarkeBumpus
NQRPAC
Larvae net
NORPAC
76
140-O
1,
No
Aug. 1957
74
140-O
17
140-O
45
0.80 Open
Yes Conical Vertical
Satsumn (NORPAC Comm. 1960a, 1960b)
60-O
200-O
Aug. 1955
33
150-O
Sept.-Oct.
1955
July-Sept.
1955
55
150-O
50
150-O
Displacement
volumeb
Displacement
volumeb
Displacement
volumeb
II
Yes
Yes
Yes
Yes
Yes
(one
ship
only 1
Yes
Yes
No
No
Wet
volume
Wet
weight
Wet
volume
Yes
Yes
Yes
138
net
0.33
Yes
No
No
55 c.300-0
--
Yes
1,335
Umitakn Mamc (NORPAC Comm. 1960a,
1960b )
Tengo Maru (NORPAC Comm. 1960a, 1960b)
Modified
Marutoku
net
Yes
II
Oct. 1957Feb. 1958
1960
Wet
volume’
Displacement
volume”
,I
II
140-O
26
22
June-July
__
81
Jan.-March
1957
net
cZ&t
Pcet-mP
..-.
191 140-O
II
147 300-O
I!
91 c.52-0 & Displacec.134-66
ment
volumec
61 200-O
Displacement
volumec
77 140-O
Displacement
volumeb
Aug. 1956
and Rinkcl 1957)
--
129 c.15&0
33 140-O
July-Sept. 1955
Sept.-Dec. 1955
Sept.-Dec.
1955
Austin (1957)
Units
reported
45
1.65 Open
Oshoro Maru (NORPAC
12.5
1.07
Opel1
Brown Bear (NORPAC
Yes
-
Vertical
Comm. 1960a, 1960b)
No
Conical
Conical Vertical
data) o
Yes Conical
data) e
-------
June--July
1955
37
150-O
Wet
volume
No
Aug.-scpt.
1955
56
200-O
Displacemcnt
volume
Yes
May-June
1956
32
150-O
Settling
volume
Yes
July-Aug.
1956
43
150-O
Displacement
volume
-
Yes
Oblique
Comm. 1960a, 1960b)
No
130
4.5 Open
0.33
EQUAPAC
Shunkotsu Mn~u (unpublished
1.8 Open
45
net 0.33
EQUAPAC
Sntsuma (unpublished
Conical
Vertical
-
-
-
_ -
-
_-
--
.-
-
-_
CIRCULATION,
Pod-P,
AND
TABLE
KW
Z
z-=--
_
--.
L
L
Mouth
Mesh
Nanlc of nct
ayE%;,
--.----
-_ - - -----
_
z
--
-
_
_
---
ZOOPLANKTON
2.
IN
(cm)
- --
.-
__ _ _-____--
Umitnkn Mnru (unpublished
-
-
-. - - -.
Cylindcr.55
Closing
Cone 2.30
F. R. V. Warrsen
Nov. 1956
data) c, *
July-Aug.
June-Aug.
1957
No
1956
Dcpth
range
(InI
17
150-O
39
42
150-O
150-O
ConUnits
current
reported PO4-P
data
Displacement
volume
Weidisplacement
volume
Yes
Yes
No
Cone
Vertical
with
cylinder
front
1956)
(C.S.I.R.O.
32-52
(C.S.I.R.O.
1951, vol. 1) stas. 1-12,
1951, vol. 3) stas.14-45
Derwent ZZunter (C.S.I.R.O. 1959)
B.A.N.Z.A.R.E.
(Sheard 1947)
stas. 206-213
April- July
1932
Dec. 1933
Feb.-Apr. 1936
Feb. Mar. 1938
Dee. 1938Jan. 1939
June 1951
May-Oct.
1938
May-Sept.
1948
Nov. 1957
ObliqueMar.
1930IMar. 1931
71
100-O
Displacement
volume
Yes
15
100-O
No
8
100-O
Settling
volumeh
Displacement
volume
II
1,
7 100-O
11 c.125-0
Yes
No
No
112
net
Orsom ZZZnet 0.36
Closing Yes
50
EQUAPAC
Orsom ZZZ (Legand 1957
Annex I, column B )
Orsom ZZZ (Legand
1958, series I-XVII)
Orsom ZZZ (Rotschi
et al. 1959, Table 1)
Orsom III
N”%bcr
obscrvations
141
70
F. R. V. Wnrreen
Total,
---______
=-~~-~~~
net
DZscovery ZZ (Foxton
Total, N70V
=
Period
Oshoro Maru (Hokkaido U. Fat. Fish. 1957)
Hokusei Mnru (Hokkaido U. Fat. Fish. 1958)
Total, NORPAC
N70Vs
0.239
297
PACIFIC
Continued
.-_--
L~;g)th 0 en or FlowcFosmg meter Shape TE:lof
L
diamctcr
THE
Ho&.
Sept.-Oct.
at 10,
1956
50,150
200,
250 m
Oblique Mar. 1957Mar. 1958
May-June
1958
net
15
200-O
Wet
volume
Yes
10
300-O
200-O
150-O
100-O
300-O
Wet
volumeO
No
Wet
volumec
Yes
Wet
weight
No
55
80
Kitahnrn
0.11
22.5
0.8 Open
No Conical
EQUAPAC
Kngoshima ( unpublished data) *
Vertical
Dana net
1.0
Horiz.
150 or
200
Open
No
Conical
Aug. 1956
23
200-O
Oct. 1928Feb. 1929
51
50,100
Volume
and
per
300 m hour’s
wire
haul
length
tow at
constant
wire
length
Dana (Jcspersen 1935)
-
GRAND
TOTAL
--____-
----
-----~---____-~---
2,005
a Fish eggs and larvae and all organisms greater than 5 cm wcrc removed before measurement.
1,Organisms greater than 5 cm length were removed bcforc measurement.
c Organisms greater than 2 cm were removed before measurement.
d Fish eggs and larvae and all organisms grcatcr than 2 cm were romovcd before mcasurcment.
c Data kindly made available through the offices of Mr. Yutaka Nagaya of the Japanese Hydrographic
1 No flowmcter was used.
s Details of net in Kemp, et al. (1929).
h Settling volumes were multiplied by 0.3 (Sheard 1947, Tables I and II).
---__
Office.
Yes
298
JOSEPH
TABLE
Depth
in
meters
2
3.
The zooplankton
-.----.~_______
Net type
u3
*-“a
$j E
:
A.2
ogj
za
150-or
140-O
200-O
300-O
150-o
200-O
200-O
C.C.O.F.I.-P.O.F.I.
Marutoku + NORPAC
C.C.O.F.I.-P.O.F.I.
C.C.O.F.I.-P.O.F.I.
Larvae
Clarke-Bumpus
Kitahara
0g
z .dM
: ;
$ m fi
3
m
& A.2
H ZZe
o3
150-or
140-O
200-O
300-O
60-O
15&O
200-O
200-O
Others
C.C.O.F.I.-P.O.F.I.
Marutoku + NORPAC
C.C.O.F.I.-P.O.F.I.
C.C.O.F.I.-P.O.F.I.
C.C.O.F.1,P.O.F.I.
Larvae
Orsom III
Kitahara
Li
“0
2
0
k
L.
REID,
data grouped
J
4 20
19
1
9
4
---___~-4 20 13
16 49
8
8
8
9
4
5
4
by area, net type, and month
_-
JFMAMJ
11
JR.
31
75
3
AS
287
91
100
45
2
---
0
N
25
27
28
5
10
-D
--w----2
Totals
--.
-.
_
784
2
1
21
8
10
20
64
1
26
37
19
-- 2 __ - --_
109 419 164 62
9 115
62 32
4
34
1:
62
47
38
63
~.
33
__
2 847
836
13
2,005
21
36
29
72
10
3
16
19
1
5
13 29
_______
8 34 127
5
10
121
109
205
67
8
88
8
115 &7
9
2
11
3
7
2
4
1
6
15
957
C.C.O.F.I.-P.O.F.I.
m
d ’ 0
g “0.3
cn z.n
100-O
125-O
50 100,
3bo
-
N70V
N70V
Dana
Orsom ZZZ
3
41-27
16
12
4
1
7
8
24
this treatment is to give values that are too
low by an uncertain amount.
The data that have been plotted and contoured on Figure 4 arc expressed in units
of parts per 109 by volume ( cnG/l,OOO M” ) .
The concentrations vary from about 10 to
more than 1,600 parts per 109. Concentrations in terms of surface area vary from
1.5 m/km2 to more than 240. If the avcrage value is taken at about 50 parts per loo,
the total amount of plankton in the upper
150 m of the Pacific is estimated to be a
little more than lo9 tons (assuming the
biomass to have a density of one ton/m”).
This is about 3 times the estimated weight
of the Pod-P in the upper 150 m or about
10 times the weight of all the human beings
in the world. The smaller forms that escape
the net (including phytoplankton)
may exceed this amount. The total annual yidd of
the commercial fisheries of the world is
about 745 of this weight.
The zooplankton volume is distributed
very much as is the Pod-P. The volumes
are high in the cyclones and in the eastern
boundary currents, and low in the anticyclones. They are relatively high in a zone
5
17
3
12
2
1
12
11
3
9
101
11
35
1 23
38 T&l
170
I
along the equator and in two zones north
and south of the equator, corresponding to
the equatorial divergence and to the two
current boundaries mentio,ned before.
The charts that Hentschel and Wattenberg ( 1930) prepared for net plankton and
POh-P in the central and southern Atlantic
indicate a close correspondence between
the two quantities.
Friedrich (1950) has
filled in the plankton map in the north, and
the high latitude values of the North Atlantic are seen to be as great as those in the
South Atlantic.
That the plankton volumes should be
high in high latitudes and in eastern boundary currents could be anticipated
from
work in the Atlantic at least as early as that
of Hentschel (1928).
Hentschel (1936)
went so far as to prepare a schematic chart
of the zooplankton
concentration
in a
theoretical ocean intermediate in size and
shape bctwcen the Atlantic and Pacific, in
which concentrations are high in high latitudcs and in the eastern boundary currents
and in two tongues extending from the eastern boundary currents part way across the
ocean in the North and South Equatorial
CIRCULATION,
PO4-P,
AND
ZOOPLANKTON
Currents. Schumacher ( 1946) has related
the zone of lowest zooplankton population
in the South Atlantic to the convergence
within the subtropical anticyclone.
A number of authors have discussed
plankton volumes in various parts of the
Pacific. Graham ( 1941), in a discussion of
the central equatorial Pacific based on
CARNEGIE data, found relations between
Pod-P and hydrographic
features, Sheard
(1947) treated the Australian-Antarctic
quadrant. King and Dcmond (1953) and
King and Hida ( 1957), in their discussions
of zooplankton abundance in the central
Pacific, found the highest volumes at the
north edge of the (North)
Equatorial
Countercurrent
where the pycnocline
is
shallow.
They noted also a large-scale
correspondence between the zooplankton
volume and Pod-P distribution.
Bogorov
and Vinogradov (1955) mapped the values
off the Kurile Islands. Holmes, Schaefer,
and Shimada (1957) and Brandhorst (1958),
in mapping the zooplankton volumes in the
eastern tropical Pacific, related them to the
thermocline
topography.
The continuous
and systematic zooplankton measurements
of the California Cooperative Oceanic Fisheries Investigations not only allow the area
of the California Current to be included on
the chart with more confidence than any
other area, but allow seasonal and non-scasonal studies. Thrailkill’s work ( 1956, 1957,
1959, 1961) indicates that the volumes
mapped ( Fig. 4) for the California Current
region, which were taken in July and August 1955, are not at the seasonal peak of
zooplankton volume, but at some time past
it, and that the year 1955 was not especially
high or low, but moderate for the decade
1950-1959.
The correspondence between zooplankton
volume and Pod-P in the California Current has been shown by Reid, Rodcn, and
Wyllic ( 1958) to hold remarkably well in
some data such as those taken in July 1950
by the California
Cooperative
Oceanic
Fisheries Investigations.
Even small-scale
tongues of zooplankton and P04-P correspond quite closely. Any reasonable allowancc of time lag for growth renders this
IN
‘ITIE
299
PACIFIC
close agreement baffling. It was suggested,
not that these zooplankton volumes grew
large from the immediate product of the
phytoplankton in the rich tongues of Pod-P,
but rather that both zooplankton and Pod-P
had reached high values upstream (farther
north) and that the tongues of water forced
offshore by the northwesterly winds merely
retain both high zooplankton
and high
P04-P values.
TRANSPORT
OF THE
PLANKTON
How much does the volume of zooplankton at any place reflect that which can be
sustained there by local growth, and how
much does it reflect the influx of plankton
that has grown in other areas? The question is readily answered over much of
the Pacific. Zooplankton volumes are consistently low in the large areas within
the anticyclones, and transport into these
areas is slow and from markedly different
environments.
It is inferred that the zooplankton volumes are produced locally and
represent an equilibrium
between the nutrients available there and the needs of the
plankton.
Over the rest of the ocean the question
cannot be answered so readily. Possibly the
nutrients along the axis of the subarctic
cyclone could sustain a larger volume of
zooplankton than the divergence will allow
to accumulate.
Surface divergence takes
place and PO,-P is high. Zooplankton
volume is high over most of the cyclone,
but a local minimum is seen along the axis
(Fig. 4). The water brought up from below
is high in nutrients but is presumably
deficient in surface forms, If phytoplankton volume may double in a few days but
zooplankton volume requires a longer time,
the maximum volume of zooplankton may
be produced only after a time lag in which
the Pod-P has decreased and the population has moved some distance from the
center of the divergence.
Some part of the rich zooplankton in the
northern part of the California Current is
brought in by the west wind drift from the
dense subarctic populations (Fig. 4). The
volumes rise off Cape Mendocino and Cape
300
FIG.
upper
JOSEPH
Distribution
4 (a).
150 m of the Pacific
L.
of zooplankton
volume
Ocean, station positions,
Blanco and in the other upwelling regions
along the coast, indicating that not only the
high northern volumes, but even higher
volumes ccan be sustained. This plankton
is swept southward with the flow, and undoubtedly accounts for a great part of the
south of
plankton
volume immediately
Point Conccp tion. The monthly plankton
volume ch‘arts of the area of the California
Current from 1949 through 1958 (Thrailkill
1956, 1957, 1959, 1961) illustrate this point
quite clearly. The volume declines very
rapidly with distance to the south of Point
REID,
JR.
(parts per log by volume)
and contours.
in approximately
the
Conception, and presumably, since more
plankton flows in than flows out, the growth
rate is negative and the population is not
being sustained, except perhaps quite near
the coast, by local growth.
After reaching a minimum near the tip of
Baja Cahfornia (Fig. 4) the nearshore values
rise again, indicating that the growth rate
has changed from negative to positive.
Since there is no break in the Pod-P distribution (Figs. 2 and 3) or in the flow (Fig.
I), but a strong rise in the temperature of
the water, it is speculated that the decline
CIRCULATION,
FIG.
upper
Pod-P,
AND
ZOOPLANKTON
4. Variation
in phosphate concentration
of lake water
150 m of the Pacific Ocean, shaded by values.
along southern and Baja California may
represent the extinction of the more northerly forms by the rising temperature. South
of this area, the zooplankton volume rises
again. Since temperature continues to rise
along the flow, it seems unlikely that the
increase in zooplankton volume represents
a recrudescence of the northern forms. It
is suggested, therefore, that it represents the
growth of warmer-water forms in the still
relatively rich water from the north. An
example of the introduction of such a warm-
IN
THE
stored
PAClFIC
in an iodine-treated
1-L poly-
water form from both the west and the
south has been given by Berner and Reid
(1961).
In addition, the roughly inverse relation
of zooplankton volume to temperature in
the California Current may be taken to
imply that the northern forms predominate
there. This inverse relation is indicated by
a comparison of the volumes at 16 stations
between Point Conception and Punta Eugenia, averaged for each year in the months
from February through August, with the
302
JOSEPH
L.
corresponding
10-m temperatures.
This
comparison was made by Reid, Roden, and.
Wyllie ( 1958) in a paper dealing with the
California Current only, and their graph is
reproduced and continued in Figure 5. Although they were discussing a possible relation to nutrients, they stated ( p. 54) “In.
deed, if there is no direct relation between
zooplankton growth and temperature, the
relation shown between the temperature as
an indirect measure of nutrients and zooplankton as an indirect measure of phytoplankton is better than would be expected,
and grcatcr irregularities
almost certainly
will be found in subsequent data.” However, when one considers the distribution of
zooplankton volume in the area upstream
from the California Current, it is possible to
speculate, as in the above paragraph, about
changes in the nature of the zooplankton as
well. It is in the years of low temperature
in the California Current (and presumably
greater influx of subarctic water)
that
volumes are highest. High tcmpcraturcs
arc usually accompanied by lower pl,ankton volumes, although there appears to be
a minimum below which the values do not
fall. This minimum may comprise the local
forms only or it may be bolstered by incoming forms from the south and west
( Berner and Reid 1961) . Possibly if the
temperature should rise even higher than
the 1958 and 1959 extremes, warm-water
forms would appear from the southeast in
sufficient quantity to cause the volume to
rise with temperature.
In cold years the high volumes extend far
to the south and in warm years they retreat
to the north. Distributions
in a cold year
(1956) and a warm year (1958) are shown
in Figure 6 (taken from the work of
Thrailkill 1959 and 1961).
A similar shift from cold- to warm-water
forms may occur near 20”s along the coast
of South America, but the data are less complete there. The data in the western Pacific
are consistent with the location of a shift
from warm- to cold-water forms off the
coast of Japan, but with perhaps a mixing
of the two forms for some distance along
REID,
JR.
FIG. 5. Temperature
(“C) at a depth of 10 m
and zooplankton in the upper 140 m (parts per log
by volume)
averaged
from
February
through
August for each year from 1949 to the present
(continued
from Reid, Roden, and Wyllie
1958,
who included data through 1956 only).
the eastward
Current.
CONCLUSION
extension
AND
of the Kuroshio
SPECULATIONS
The concentration of Pod-P at the surface and at 100 m is related to the circulation of the ocean. At the surface it is high
in regions of horizontal divergence and low
in regions of convergence. At 100 m the
POh-P is low where the pycnocline is deep
and high where it is shallow, and thus corresponds closely to the current systems.
Zooplankton volume has been shown to
vary almost everywhere with Pod-P. As a
major exception, the center of the subarctic
cyclone is high in Pod-P, but only moderate in zooplankton volume. The hypothesis is offered that the divergence rate is
too great for a high zooplankton volume to
accumulate even though growth may be
rapid.
Ekman ( 1953) maintains the generally
accepted view that the main regions of
pelagic fauna consist of a warm-water region and a northern and a southern coldwater region. The close correspondence of
both the PO*-P (as an indicator of nutrients)
and the zooplankton volume to the system
of gyres suggests that the gyres themselves
may offer a more effective classification.
Their relatively narrow range of latitude
20
FIG. 6.
I
1300
OCCUPIED
I
Zooplankton
0 STATIONS
do0
in the upper
I
tr
I
1100
:oo
2o”
volume
140 m of the California
0
Current
I
130°
I
OCCUPIED
I2bO
I
0:
n
-09
in 1956 and in 1958 (parts per log by volume).
STATIONS
301-900
OVER 900
m
301-900
OVER 900
l
34- 100
#gJ 101-300
o-33
101-300
:: ::
34- 100
o-33
i0”
30’
30
IO0 4c
40
o
0
I
110
!O”
304
JOSEPH
results in their having a relatively narrow
range of properties.
Particular
features
(surface convergence in the anticycloncs,
coastal boundaries along much of the cyclones) tend to confine the individuals
within the gyres.
The observed distribution of zooplankton
volume lends considerable weight to Damas’
( 1905) speculation
that ( p. 22) “Le
mkchanisme de la circulation joue done ici
le r8lc principal pour la conservation de
l’esp&ce et la creation d’un plankton speciil.”
and (p. 23) “. . . la rotation supcrficielle des
eaux est l’un des Uments le plus importants
dc la persistence de la vie a la surface de
l’ocdan.”
As a result, it is speculated that the
greater part of the zooplankton volume
within a gyre may bc made up of forms that
are found generally throughout the gyre,
but only in much smaller quantities in the
adjacent gyres. If this is so, the great zooplankton communities are: the subarctic
and the subantarctic which are high in
volume (and which may bc quite similar);
the subequatorial,
which is modcrate to
high in volume; and the subtropical, which
is low in volume.
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oceanographic
and fishery
data, Marquesas
Islands Area,
August-September,
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U. S.
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-.
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1960. Oceanic investigations
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--.
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-,
AND T. S. AUSTIN. 1954. Mid-Pacific
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-.
1944. Station list, 1935-1937,
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-.
1947.
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-.
1949.
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-.
1957. Discovery
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1945.
Observations
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l?04-I?,
AND
ZOOPLANKTON
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1941. Plankton production
in
relation
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HELLAND-HANSEN,
B., AND F. NANSEN. 1909.
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HENTSCIIEL, E. 1928. Die Grundziigc der Planktonverteilung
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Internat. Rev. Hydrobiol.
Hydrogr., 21: l-16.
-.
1936. Allgemcine
Biologie
des Siidatlantischcn
Ozeans.
Deutschcn
Atlantischen
Expcd., Meteor 1925-1927, Wiss. Ergeb., 11:
1-344.
-,
AND H. WATTENBERG.
1930. Plankton
und Phosphat in der Oberfkichenschicht
dcs
Siidatlantischen
Ozeans.
Ann. Hydrogr. Mar.
Meteorol., 58 : 273-277.
HIDAKA, K. 1958. Computation
of the wind
stresses over the oceans.
Rec. Oceanogr.
Works Japan, 4: 77-123.
HOKKAIDO UNIVERSITY, FACULTY OF FISEIERIES.
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