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Some features of zooplankton,distribution in the
Gulf of Mexico
•
by A. N. Kolesnikov •
•
Original ,title: Nekotorye cherty raSpredelehiya zooplanktona
v Meksikanskom zalive
From: Issledovaniya Tsentral'no-AmerikanskYkh morei
(Central-American Marine Research), 3 : 64-79, 1971
Translated by the Translation Bureau(ADL) Foreign Languages Division
Department of the Secretary of State of Canada
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Vancouver, B. C., •
1973 .
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Some features of zooplankton distribution in the Gulf of Mexico.
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Nekotorye cherty raspredeleniya zooplanktona v Meksikanskom zalive.
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Nekotorye cherty raspredeleniya zooplanktona
v Meksikanskom zalive.
Issledovaniya Tsentral i no-Amerikanskykh morei
Vol. 3,
pp. 64 - 79,
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SOME FEATURES OF ZOOPLANKTON
DISTRIBUTION IN THE GULF OF MEXICO
By A. N. Kolesnikov
This article sets forth some of the features of horizontal and vertical [64]*
distribution of zooplankton throughout the water area of the Gulf of Mexico
that emerged in the course of the processing of data obtained by the author
during the Soviet-Cuban expedition of 1964-65.
Interest in this region of
the World Ocean arises not only from practical tasks at hand (intensive
fisheries and non-fisheries production) but from theoretical ones as well.
Procuring knowledge of processes occuring in the depths of the Gulf of Mexico
is especially interesting in the sense of the understanding it brings of the
hydrobiological regime of the North Atlantic. The appearance of types of
plankton connected with particular water bodies and the analysis of their
distribution can help in investigating the movement of water bodies of various
* Numbers in right-hand margin indicate corresponding pages in original.
50S-200-10-31
7530-21-029-5332
-2
r.
origins. Finally, it is of no small importance to observe the distribution
of one type or another of zooplankton from the point of view of the accumulation and transport by them of radiation pollution, a real problem in the
Gulf of Mexico [Polikarpov, Zattsev et al, 1968].
However, until comparatively recently the Gulf of Mexico has been insufficiently studied in respect of zooplankton distribution. The works of
•
Suarez Caabro [Suarez Caabro, 1954, 1955], Tokioka [Tokioka, 1955], Tokioka
and Suarez Caabro [Tokioka y Suarez Caabro, 1956], Grice [Grice, 1960], as
well as a series of works in the collection "Gulf of Mexico...", 1954 [Banner,
Moore, Pierce, Schmitt, Saars] are basically devoted to zooplankton in limited
sectors of territorial waters.
Studies by Soviet scientists 9f z99p1ankton in the Gulf of Mexico have
been conducted since 1962 and have started to be published just recently.
Initial data on quantitative distribution of zooplankton in the Gulf of
Mexico are contained in artic1e5 by participants in the Soviet-Cuban marine
expedition N.S. Khromov [1965a, 1965b, 1968], A.N. Kolesnikov and A. Alfonso
[1966]. However, almost none of these works can make pretensions to a high
degree of accuracy inasmuch as th g PaPritY of them were based on the determination of the volume or, at the very best, of the weight of seston in which zooplankton comprises sometimes even the minimal part.
Thus, according to our
data, in the region between the island of Cuba and the Dry Tortugas islands
the content of zooplankton in seston, whose weight was determined on torsion
scales, amounted in September 1964 in the 0 - 25 metre layer to 26%, in the
25 - 50 metre layer to 56% and in the 50 - 100 metre layer to 66%.
The
qualitative composition of zooplankton was also determined by a cursory
- 3
viewing of samples under the microscope. Only in our 1968 work was the
number and biomass'of zooplankton for two regions of the Gulf established
by the computer scale method.
In the present work, almost the entire water area of the Gulf is
considered except for its northern portion and for the Florida Shelf. The
[65]
methodology of taking samples and of the computer scale data processing has
been published by us earlier in the prior edition of the collection that
came out in 1968.
From data set forth in Table 1 it can be seen that altogether 190 samples
taken from 25 stations were processed. Twelve stations were executed during
daylight hours, 9 in darkness, 4 throughoutthe 24-hour day (out of data from
24-hour station 10, only one series was processed).
From the illustration it is clearly seen that stations were situated
basically along sections cutting the Gulf in various directions. 16 stations
were executed byond the shelf, 9 in shelf waters (thé shelf area is signified
in the illustration by a solid line).
Meteorological conditions in the work area were favourable except for
the Yucatan Channel where a brewing storm interfered with the conduct of
resea'rch.
All samples were obtained within a span of four-and-a-half months
during the autumn-winter period.
Plankton distribution by amount and biomass was investigated by layers:
in layers 0-100, 100-200, 200-500 metres and 500-1,000 metres. Naturally,
most attention was devoted to the most active, and richest in living matter,
0-100 metre layer, the more so since more data were collected in that layer
than in the rest.
4
Table
1
DESCRIPTION OF REGION AND TIME
OF OBTAINING SAMPLE
0 0
Station
number
H
Paraels
N. long
N.lat.
ta■
Q)
4-)
PL. cO
CD CO
A
2V 01'
9' 0
3
cm ,
23' 41'
5
7
9
24° 15'
2'5 33'
L.
5 (cyr...eye 25 -. 20'
25' 34'
22
22 ° 31'
6(c y'T.) e
JO
25
23'' 00'
27
29
19' 25'
7 (cyr.) :`
00'
32
20°-10'
34
19°42'
36
18«> 39'
•
38
• 20' 11'
39
21°-13'
40
22' 20'
10 (cyT.) A
93'09'
43
68
71
74
(cyr.)
Layer
21° 49'
21" 43'
21 - 33'
s)3" 25'
850 • 500
1000
2100
500
1590
500
1020
100
600
1650
• 1000
80
•
87
30
37
90
95
1000
2300
500
2910
200
3600
Ç 100
106
9,s50
1000
1.000
2200
500
800
45
50
10
.
12
43
49
90
93
83° 17'
83° 15'
83° 11'
83° 10'
83° 00'
95° 17'
96 - 42'
97° 01'
97° 27'
96 ° 33'
95° 39'
94 ° 48'
96° 02'
95' 05'
93° 44'
93' 43'
93° 35'
90° 98'
90 ° :38'
° 59.'•90
91° 06'
85° 01'
85' 49'
86" 37'
87° 60'
3840
• 695 .
2000 •
40 ,
540
1000
200 ;
100 .
30
500
VI
0
$-.1
ri
W
473 44
el.
Date
0 0 0
CO
0
CO
Z
,
i
6
7
6
4
7
36
1
20
6
i
5
i
' 20
7
3
1
1
4
I.IX 964
1.1X 964
2.IX 964
. 2.1X 964
2.1X 964
7.X 964
8.X 964
9.X 961
10.X 964
12.X 964
1.3.X
964
964
13.X
24.X 964
26.X 964
27.X 961
27.X 964
23.X 961
1.X1 964
1.X1 964
2.X1 964.
7•
3.X 1 1964
13.X11 1961
5•
416.XII 1964.
17.X11 1964
2.
15.1 1965
12 !
Local
time
8-10
18-24
7-10
16-17
23.30-24
14.30-18
- •
18-18.30
15.30-18
7.30-9
21-21.30
.12.30-17
6.30-9
19-20.30
6-6.30
6-6.30
11-11.30
• « 7.-7.30
(celnisl 3)- krwies
5-7.30 .
1.30-3
18-21
10.30-11
0-1
0 100 metres. According to our data, average zooplankton content
-
in the surf icial 100-metre layer of the ocean zone of the Gulf of Mexico was
3
3
360 specimens per m in number and 22 mg/m by biomass. For the shelf of the
Gulf of Mexico, 2,850 spec./m
3 and about 100 mg/m 3 respectively.
166]
- 5
/ ! ^ •i ' -w^
GÇ^^
rS
,^.
r^ • 71 i
ONE-Till E
^ 4-Houe5,TATIeNS
7©-Cymrvrn;e
071a11uUd
Konct<<ec,seutioe pacrueze.ietnte 300f1:(aE[Y.î01Sa B
O-Pa3c^iLre
cmarruuu
XPKC1(K,111choN1 3a7{t6e
1- 1u!CaeinlccTb <500 s:;:r,:n', 6uoraacc.< <25 ::j/.l.': °- 41c.RCaeocrb
j00
3 - 9}1C ie}IIlOCTb 500--100f) 7ti.97.ü3, 61!U:tar.Ca 21j--5j
STqTI,fPlâ
(cnoïi
0-100 :t):
1000-2000 ans/si'. fno%lacca 50-.
y:.^l)00
4 - 4IICOff(FlOCT6
G;w^c;cca s 10.vaj,113.
QUANTITATIVE DISTRIBUTION OF ZOOPLANKTON IN THE GULF OF MEXICO
(LAYER 0-100 metres)
1-count <500 spec./^3, biomass <25 mg/m3; 2-cou^t 1,000-2,000 spec./1 3,
biomass 50-100 mg/m ;-count 500-1,000 spSc./m , biomass 25-50 mg/m
4-count >2,000 spec./m , biomass >100 mg/m
If our data on biomass are compared with data obtained by various
researchers in other water areas it is easy to regard the oceanic zone of
the Gulf of Mexico, by quantity of zooplankton, as being a part of ologotrophic waters of the Atlantic [Yashnov, 1961; Kanaeva, 19651, in which the
biomass of plankton does not exceed 100 mg/m3. Comparison of the quantitative
characteristics of zooplankton in the Gulf of Mexico with,data on the Mediterranean Sea obtained also by the computer scale method by G. N. Mironov [1964],
6
L. I. Sazhina [1965] and A. A. Shmelova [1965], indicates the biomass of
zooplankton in various parts of the Mediterranean Sea fluctuating from 13
3
to 27 mg/m , i.2., the Mediterranean Sea, in quantity of zooplankton, hardly [67]
dif fers from the oceanic zone of the Gulf 'of Mexico.
The quantity of zooplankton in the Gulf of Mexico is distributed unOur data made it possible to note sectors in the Gulf of Mexico
evenly.
with differing zooplankton content. The whole surficial 100-metre layer of
the water area of thé Gulf under study was divided into four different (by
quantity of zooplankton) zones (see illustration).
To the first zone belong those regions of the Gulf in which quantity of
3
zooplankton exceeds 2,000 spec./m , while the biomass fluctuates from 150 to
200 mg/m.
In this zone are included Campeche bank, a fairly narrow strip
running along the Mexican coast which widens at the mouth of the Rio Grande
(region of station 22), as well as to the south of Campeche bay and squeezes
up almost completely against the shore as it extends . south from the mouth of
the Rio Grande and, in addition, according to data of V. K. Moryakova [1966],
a narrow near-shore strip along the northwest coast of Cuba. The northern
shelf of the Gulf at the mouth of the Mississipi and the western shelf of the
Florlda peninsula were not encompassed in our samplings but, judging from
data of N. S. Khromov [1965, 1968], they too are characterized by maximal
zooplankton content.
To the second zone with an amount of zooplankton in the 1,000 - 2,000
spec./m
3
range, and a biomass range of 50 - 150 mg/m
3
we assign a relatively
small portion of the shelf to the west of Yucatan Channel (region of station
74) and the eastern slope of Campeche bank lying beyond the shelf (region of
24-hour station 14).
7
■••
3
The third zone (zooplankton count from 500 to 1,000 spec.1m , biomass
3
25-50 mg/m ) includes both ocean regions -- Campeche bay, a section adjoining the south end of the Dry Tortugas islands (region of station 9) and the
strip of the Mexican shelf running from north to south over depths of about
100 metres (region of 24-hour stations 6 and 5).
Finally the poorest in zooplankton fourth zone, the open part of the
Gulf situated between Campeche bay to the south and the shelf of the Missis-
sipi mouth region to the north, as well as the Yucatan Channel.
To this
selfsame zone must also be assigned the south-west portion of the Mexican
shelf above a depth of 100 metres (region of 24-hour station 7).
Thus the first zone of increased zooplankton content is situated
exclusively in the shelf region, the second zone both in the shelf region
(region of station 74) and in the oceanic region (region of 24-hour station
14), the third and fourth zones primarily oceanic but partially extending to
the shelf as well.
•
Our-regionalization of the Gulf of Mexico by zooplankton distribution
coincides generally with seston distribution according to N.S. Khromov
[1965a, 1965b, 1968 1 . N.S. Khromov assigns to the most productive regions
of the Gulf, together with the northern and Florida shelves, Campeche bank,
and also the region to the west of Campeche bay where zooplankton content
is higher than in the greater part of the Gulf.
According to data from the
second period of the Soviet-Cuban expedition [Shuvalov et al 1965; Belousov
et al 1966],
in the southern part of the Gulf of Mexico there are several
zones of intensified biological activity.
In addition to Campeche bank,
the above-named writers assign to them the western part of the Yucatan Channel,
the region in the vicinity of the Dry Tortugas islands as well as the portion
8
of Campeche bay corresponding to our station 32. This summary, as also
the conclusions of N.S. Khromov, has been made on the basis of establishing
the volume of seston. however, it also accords to some degree with our data
j
on zooplankton.
Layer 100-200 metres.
All 13 stations, on which this layer touched,
[68]
were set up in the oceanic zone. Average zooplankton count amounted to 65
spec./m3, i.e., almost six times fewer than in the 100-metre layer above it,
while for the biomass it was 5 mg/m3, four and a half times less than in the
0-100 metre layer.
However, these parameters were also unevenly distributed
in the Gulf and fluctuated: count -- from 2.to 172 spec./m3, biomass -- from
0.5, to 21 mg/m3. The richest zooplankton content in this layer was found
in the eastern part of the Gulf (region of stations 1 and 3), as well as in
the regions of stations 27 and 36, least of all in the region of station 19.
It should be pointed out that in the 100-metre layer lying above also, the
least quantity of zooplankton was registered at station 19 as well.
Layer 200 - 500 metres was demarcated by 12 stations (1, 3, 5, 7, 19,
25, 27, 32, 34, 36, 43 and the 24-hour station 14). Average zooplankton
count in this layer amounted to 22 spec./m3, i.e., almost three times fewer
than in the 100-200 metre layer, biomass -- 2 mg/m3, also two and a half times
less.
The count fluctuation span is here also fairly wide -- from 4 to 35
spec./m3, the span of fluctuation of biomass a good deal smaller -- 1 to 4
mg/m3.
The greatest zooplankton content in this layer was noted at stations
27, 32 and 43, the least at station 19, where the quantity of zooplankton
was minimal in higher layers as well.
Layer 500 - 1.000 metres. In this layer, data was collected altogether
from 6 stations situated in various regions of the Gulf (stations 3, 19, 25,
32, 34 and 43).
Average quantity of zooplankton appeared to be equal to 8
3
specimens, biomass -- about 1.5 mg in 1m . Zooplankton content fluctuation
3
was in the 6-14 specimen range, biomass -- 1-2.5 mg./m .
Thus, in this deep
layer zooplankton is distributed throughout the whole water area more evenly
than in higher layers.
From the foregoing it follows that the overall picture of quantitative
distribution of zooplankton in the Gulf of Mexico corresponds by depth in
its overall features to what takes place in other tropical regions of the
World Ocean [Vinogradov, 1968].
In tropical waters of the Pacific and Indian
Oceans, according to M. E. Vinogradov, the size of the biomass of zooplankton
reduces to 5-10 mg/m
3 in the 100-500 metres layer, i.e., approximately the
same as in the Gulf of Mexico.
It is known that quantitative distribution patterns of plankton arise
from particular features of the hydrological and hydrochemical regime in
various sectors of the water area. According to our data, maximum quantity
of zooplankton in the Gulf of Mexi-o is confined to water bodies with a
water temperature of 26.2-28.9 ° and a salinity of 36.2-36.8 0 /oo.
Apparently
these conditions are to be regarded as optimal for zooplankton in the Gulf
of Mexico.
The rich plankton content of shallow waters (Campeche bank, the nearshore zone of the shelf) is caused first of all by accelerated regeneration
of biogenic elements in these regions as the result of intensive mingling
of waters [Belousov et al, 1966].
Of interest is the expansion of the zone of biologically active waters
on the Mexican shelf in the region of station 22 and of the 24-hour station 5.
••■
•
-
10
-
This phenomenon is considered in another of our papers in this collection.
Probably we are dealing here with the influence of coastal effluence around
the mouth of the Rio Grande.
Bay
The increased zooplankton content in bampecheiby comparison with other
open regions of the Gulf of Mexico is explained undoubtedly by some sort of
ascent of deep lying waters in the region of station 22 [Belousov et al,
1966; Bodanov, 1965b].
[69]
However, the possibility was not be rejected of the
replenishment with plankton of the waters of Campeche bay as the result of
delivery of a considerable quantity of plankton organisms by that branch of
the Yucatan current which, according to D. V. Bodanov [1965b] and G. D. Vasirev
and Yu. A. Torin [1965], deflects, emerging from the Yucatan Channel, to the
north-west, and flows across Campeche bank into Campeche bay.
Earlier [1968]
we had already expressed this supposition, which it was later possible to reinforce with new data both concerning the bay and Campeche bank.
The paucity of plankton in shelf waters above the 100-metre depth level
to the east of Veracruz (region of 24-hour station 7) is possibly explained
by the descent of surface waters compensating for the ascent of deep lying
waters in the region of station 32 situated farther to the east.
The increased quantity of zooplankton to the east of Campeche bank (24hour station 14) is partially connected with the proximity of the bank,
testified to by the fact also of the presence in samples taken from this station of a large quantity of individual specimens of a number of neritic species,
but more, perforce, because of the fairly intensive ascent of deep lying waters.
The reduced temperature and salinity of water in surface layers at this station confirm the hypothesis of an ascent of waters, but more clearly do they
point to that presence in surface layers even in daylight of many species
1
•I '
-
11
-
peculiar to the bathypelagic complex and inhabiting depths usually of more
than 500 metres (Eucalanus elongatus, E. attenuatus, E. monachus, Rhincalanus
cornutus et al).
Lelus attempt in more detail to trace the connection between the quantitative distribution of zooplankton and hydrological patterns by the section example which we drew from the island of Cuba to the Dry Tortugas
island (stations 1, 3, 5, 7 and 9). The hydrological description of this
section through the western part of the Straits of Florida, according to
data of a number of authors [Ivanov et al, 1965; Vasil'ev and Torin, 1965;
Belousov et al, 1966; Rossov and Santana, 1966; Rossov, 1966; Smirnov,
Mikhailov, Rossov, 1966] is as follows: a strong Caribbean, or Yucatan
current enters the Straits of Florida from the Gulf of Mexico, which in
this region is called the Florida current. Its axis on the traverse of the
Dry Tortugas islands deflects toward Cuba.
Through the deep part of the
Straits passes a countercurrent from the Atlantic which, by virtue of the
peculiarities of the bottom topography, rises to the surface at the Florida
shelf (the northern part of our section), causing the permanent ascent of
deep waters in this region. Then it goes farther along the Florida coast;
in summer this countercurrent reaches the mouth of the Mississipi. A countercurrent also runs along the coast of Cuba to the west which, according to
Yu. A. Ivanov [1965], is a branch of the Florida current that had turned back
in the Old Bahama Channel. This countercurrent, having run into the main
part of the Florida streandrops under it and in so doing causes zones of
surface water descent in the southern part of the section adjoining the Cuban
shelf (region of station 1).
to be permanent.
V. V. Rossov [1966] believes this descent zone
Nearer to the Cuban coast the ascent is noted too of deep-
lying waters, but more feebly than at the Florida shelf. Thus, the section
- 12 -
that we described runs through two permanent zones of deep-lying water
ascent -- in its northern part and in the south, as well as through the
permanent (according to the opinion of Rossov) surface water descent zone
at the Cuban shelf.
Let us see how the quantitative distribution of zooplankton accords
with this picture of hydrological phenomena on the section Cuba-Dry Tortugas.
In the 100-500 metre layer of all five stations there are no sharp dif-
[70]
ferences, neither in count nor in biomass. As for the 0-100 metre layer,
here the fluctuation span between stations by quantity of zooplankton is
fairly wide -- from 640 spec./m3 in quantity and 43 mg/m3 in biomass at
station 9 to 120 specimens and 21 mg. per 1 m3 at station 7. At almost all
stations on the section maximal zooplankton quantities were confined to the
very surface layer, and only at station 1 did maximal quantities move into
the 25-50 metre layer.
Stations 3 and 9, at which the greatest number of zooplankton was
registered in the uppermost 100-metre layer, were executed at night, however
between the two of them there is a substantial difference: whereas at station 3 both count and biomass of zooplankton are very large in the 0-10 metre'
layer but fall by more than 10 times in the 10-25 metre layer, and then rise
a little in the 25-50 metre layer, at station 9 the quantity of zooplankton
throughout the 100-metre layer is considerably higher than at station 3,
and evenly decreases as one goes deeper. Whertas in the first instance we
are probably dealing with the nocturnal ascent of zooplankton into the surface
layer, and from the deeper layers into the 25-50 metre layer, at station 9 the
reason for the increased zooplankton content in the surface 100-metre layer
does not evidently lie in vertical migration. As between these stations there
-
13
-
are severaldifferences in the nature of aquatic masses: the temperature
of the water in the surface layers at station 9 is lower than in the
corresponding layers at station 3, but salinity, on the contrary, is higher.
Thus in September 1964, the top 100-metre layer at station 9 was characterized
by aquatic masses of reduced temperature, increased salinity and increased
plankton content.
During the fifth voyage of the expeditionary vessel "Akademik Kovalevskii",
on February 22, 1965, during morning hours (9:00 - 10:00)
in this region we
executed station 82 on the same latitude as station 9 but somewhat to the
west.
Processing of data from this station showed that both in a different
season and at a different time of day the amount of plankton in this region
remains fairly high.
Water temperature was also considerably iower than at
other stations of the section.
From this it follows that the characteristics
of stations 9 and 82 are sufficiently stable and are connected with some sort of
permanent phenomenon.
Referring to data of hydrological studies, we noted above the intensive
and permanent ascent of deep lying waters at the southwest Florida shelf.
In
the literature there are also indications of an increase in this region of
both phytoplankton [Zernova and Mola, 1965] and seston as a whole [Khromov,
1965, 1968; Shuvalov et al, 1965]. Along the section that we made through the
Straits of Florida we evidently touched on the extreme southern section of
this ascent zone directly adjoining the Florida shelf.
Let us inspect stations 5 and 7, in the surface 100-metre layer, which
were registered during the observational period of the least quantity of zooplankton. Both these stations are situated in the central zone of the Strait.
The Zooplankton count in the 50-100 metre layer is especially paltry --
-1.43
altogether 6 spec./m . Neither water temperature of this layer nor salinity
differ greatly from analogous parametres in the corresponding layer of nearlying stations. The reason for such plankton impoverishment in this layer
at station 5 is evidently to be sought in other factors at present unclear.
The overall paucity of plankton at stations 5 and 7 -- the central stations
of the section -- recalls an analogous picture at station 71 in the central'
part of the Yucatan Channel, in whose vicinity zooplankton content is also
considerably less than at stations situated on both sides of it (see paper
by Kolesnikov in the previous edition of collected papers).
This is possibly [71]
a general phenomenon for straits in this region, in whose central zone plankton
is probably unable to concentrate.
Especially interesting were data from station 1.
Earlier we mentioned
a movement of a maximum of zooplankton at this station in the 25-50 metre
layer. In addition, zooplankton content in the 50-200 metre layer at station
1 is a good deal greater than in this same layer at stations 5 and 7. This
difference is especially to be remarked if one remembers that work at stations 1 and 5 was conducted at the very same times of day. However, the
surface layer (0-50 metres) turned out here to be poorer than at all the
other stations of the section. This comparatively plankton-poor station
is situated in the vicinity of the near-shore zone C of the island of Cuba
where the zooplankton count, according to data of V. K. Moryakova and A.
3
Campos [1966], at that same period reached 2,000 spec./m , at the time that
3
at station 1 in the top 100-metre layer it was no more than 260 spec.1m .
Probably the reduction of the zooplankton maximum and impoverishment of the
surface layers should be matched with the descent zone of surface waters
discovered by V. V. Rossov during a hydrological survey done at the same .
- 15 -
time as our expedition. During the fifth voyage, at a point with the very
same coordinates as station 1, on February 21-22, 1965, the 24-hour station
15 was executed.
A series of samples was processed taken during the same
morning hours as samples at station 1. It turned out that both seasons differed considerably in quantity of zooplankton.
Both count and biomass in
the top 100-metre layer more than doubled, while zooplankton content in the
uppermost 0-10 metre layer increased by 12 times. Plankton maximum in this
case was at the very surface. Only at depths of over 100 metres was plankton
quantity in both seasons almost identical. Such a difference in samples
taken at one and the same spot, but' at different seasons, leads to the conclusion, firstly, of there being a seasonal changeability factor and, secondly,
that the descent of surface waters, established in this region in September,
is evidently not permanent, or displaces in space.
Thus, the investigation of the quantitative distribution of zooplankton
at stations of the section running from the island of Cuba to the Dry Tortugas
islands confirms hydrological data on the presence in this region at the
northern end of the section, to the south of the Florida shelf, of a local
zone of ascent of deep-lying waters, permanent in character, as well as of
a local zone of descent of surface waters at the opposite end of the section,
to the north of the Cuban shelf. As has already been indicated, the link
between hydrological phenomena and quantitative distribution of zooplankton
is well defined in other regions of the water area of the Gulf of Mexico
as well.
However, more interesting data can be obtained from an analysis of
the qualitative distribution of zooplankton.
We have very little data in the literature on qualitative distribution
of zooplankton in the Gulf of Mexico. Most interesting are the works of the
t
'- 16 Cuban researcher Suarez Caabro containing interesting data on the species
composition and distribution of chaetognaths [1955] and appendicularia
[Tokioka y Suarez Caabro, 1956]; however the author confined the study of
these groups to that part of the Gulf adjoining the island of Cuba.
Other
works of his are devoted to the qualitative composition distribution of
chaetognaths in the Gulf is also studied in the works of Tokioka [Tokioka,
1955] and Pierce [Pierce, 1954].
As for other groups of organisms, the
paper by Grice [Grice, 1960] on copepods of the genus Oithona from the Gulf
of Mexico should be pointed out.
Other works on the species composition
of various groups of zooplankton in the Gulf, especially those included in
the collected papers "Gulf of Mexico..." (1954) of Schmitt on copepods,
Sears on hydromedusae and Portuguese Man-o-Wars and Banner on mysids and
euphausids represent far from full lists of species without any of their
distribution throughout the water area. Finally, the paper by Moore from
the same collection on zooplankton of the Gulf contains nothing but an
enumeration of various plankton aggregates and indications of where they
reside. •
Likewise little is said in the works of Soviet researchers about the
qualitative distribution of zooplankton in the Gulf. The work of V. K.
Moryakova and A. Campos [1966] is devoted only to the Cuban shelf. Shuvalov
et al [1965] in a proposed list of species do not deal with the problem of
the distribution of these species either by regions
or by depths.
N. S.
Khromov in his papers refers to the distribution of several mass species in
basic sectors of the Gulf, and in his latest work [1968] he draws up a list
consisting of 13 species of copepods from waters of the Florida shelf and
compares it with a list of mass species of copepods from the region of Dakar.
- 17 However, in the papers by N. S. Khromov there is no description of zooplankton
of the Gulf of Mexico.
•
Finally, in our own earlier papers [1966a, 1966b]
in
which this probl.,...m was considered and lists of copepods and chatognaths were
submitted, we confined ourselves to only a few regions and results of field
data processing.
In the 1968 work we submitted a fuller list of species for
Campeche bay and the Yucatan Channel, and data on their depth distribution
were presented as well.
In this present Paper, on the basis of more extensive data, we will dwell
on several features of the qualitative distribution of zooplankton throughout
the water area of the Gulf both in two of its zones -- neritic and oceanic -and by depths. There were no differences discovered in the distribution of
various groups and species either laterally
or meridianally, aside from a
few exceptions which we will deal with below.
This is understandable inas-
much as the Gulf of Mexico, despite the fact that a considerable part of its
water area is located to the north of the Tropic of Cancer, may be assigned
entirely to the tropical zone of the Atlantic.
Its waters are formed in the
main from the Yucatan current which brings into the Gulf water masses from
the tropical Atlantic (Bogdanov, 1965b). The inflow of waters from the
tempeiate Atlantic through the Straits of Florida (Florida countercurrent),
passing to the north of the Gulf along the western coast of Florida and in
summer reaching the mouth of the Mississipi, is considerably more feeble
[Vasirev and Torin, 1965].
Water temperature in the surface layer of the
Gulf is very high and changes in the course of a year from 25 0 to 30 °C.,
salinity from 35 to 37 ° /oo [Bogdanov, 1965a]. All this determines the
tropical character of pelagic fauna of the Gulf of Mexico and its relative
uniformity in qualitative respects.
- 18 -
Sharp qualitative differences were discovered between zooplankton of
the open part of the Gulf and of the shelf zone although throughout the
whole Gulf both the penetration of neritic forms into the oceanic regions
and the opposite is noted [Kolesnikov, 1968]. No small role is evidently
played in all this by tidal phenomena (see paper of A. N. Kolesnikov in the
present collection).
The percentage ratio between the main groups of zooplankton in the
surface 100-metre layer by number and biomass we computed separately by
oceanic and shelf zones (Table 2).
From data in Table 2 it follows that in both oceanic and neritic zones
and by count and biomass first place goes to copepods, which is character-
[73]
istic of the entire World Ocean. However, if it is true that the copepod
count comprises about 8.0% of the count of all zooplankton in both zones,
then, by biomass, to copepods belongs only 50% of the zooplankton biomass
in the oceanic zone, and in the neritic even less than 45%. These magnitudes
are close to those obtained by us for other tropical regions of the World
Ocean.
Thus, in the Pacific Ocean, in the region of the Tuamotu islands
the percentage copepod content in the top 100-metre layer fluctuated from
83% to 91% in count and from 46% to 61% by biomass [Kolesnikov, 1967]. The
reduction of the percentage of copepod biomass in neritic zones by comparison
with oceanic is explained by a sharp increase of the quantity of other crustaceous larvae of decapods, and of ostrapods as well, which are abundantly
represented on the shelf and have frequently a much greater biomass than
copepods.
In respect of ostrapods, it bears noting that if in the.oceanic
zone their maximum, as a rule, is noted at depths below 100 metres, and in
the 0-100 metre layer they are altogether very few, then on the shelf they
- 19 Table 2
ZOOPLANKTON COMPOSITION OF THE GULF OF MEXICO
AT 0-100 METRE LAYER (IN % OF OVERALL TOTAL)
Ocean zone
Group
e.
x
Coelenterata
Siphonophora
Hydromedusa
Polychaeta
Mollusca
Crustacea
Copepoda
Ostracoda
Euphausiacea
Amphipoda
Decapoda
Enchinodermata
Chaetognatha
Tunicata
Appendicularia
Salpidae
are more numerous.
.
m
e
o
o
0
0
0
.,-1
0
0
m
21,5
20,5
0,9
1,4
1,7
64,5
50,3
1,2
9,6
0,8
3,0
1,0
3,2
4,9
4,0
0,9
m
m
cd
4"
e
o
1,0
0,8
0,2
1,0
2,7
83,2
80,0
1,9
0,7
0,1
0,4
1,8
2,1
5,8
5,3
0,5
x
x
.
"m
N
4-J
Neritic zone
0,2
0,1
0,1
0,5'
13,2
79,9
74,8
3,5
0
0,2
1,7
0,1
1,2
3,3
3,0
0,3
e
0
..-1
m
9,5
4,0
5,5
1,1
4,8
74,5
44,5
3,4
0
1,4
23,0
0,1
4,0
6,0
5,3
0,7
.
In both cases the main body of ostracodal copepods is
represented by species of the genus Conchoecia.
There are other differences between both zones as well.
In particular,
if in the oceanic zone second place by count after crustaceans goes to ap-
pendicularia, then on the shelf it goes to molluscs.
The culprits here are
first and foremost gastropod larvae which grew very abundantly during the
period of our expedition in plankton of Campeche bank; at several stations
they predominated greatly in count over other groups. N. S. Khromov [1965b,
1968] also notes mass growth of gastropod larvae on Campeche bank in summertime,
- 20 -
in autumn and in winter. The quantity of meroplankton in any case on the
shelf is considerably higher than in the oceanic zone. The number of
organisms of ineroplankton (larvae of molluscs, decapods and echinoderms) in
oceanic waters of the Gulf amounted in our 'samples to 5% of the number of
all zooplankton, while in neritic, to 15%, i.e., triple; by biomass the differences are even greater -= 6% in the oceanic zone and 28% on the shelf.
Certain differences too were discovered in terms of percentages of the
quantity of Coelenterâta.
If in the oceanic zone siphonophors predominate,
whose biomass comprises 20% of the biomass of all zooplankton, then in waters
of the shelf the biomass of hydromedusae is greater.
Thus, the shelf waters of the Gulf of Mexico differ from oceanic waters
not only by the more abundant development of zooplankton as a whole but also
in qualitative parametres -- by a large content of such groups as ostracods
[74]
and hydramedusae as well as meroplankton forms, chiefly decapods and molluscs.
Especially clearly do differences between both zones stand out in examining
the species composition of zooplankton.
complexes of neritic and oceanic species.
It proves possible to distinguish
However in the Gulf of Mexico, by
virtue of the peculiarities of water exchange the whole of the oceanic part
of the"water area is "littered" with neritic forms, while into the shelf zone
sometimes in large quantities arrive oceanic species [Kolesnikov, 1968]. Some
of the peculiarities of distribution of various species as between both zones,
oceanic and neritic, and by depth, we will consider by reference to the
copepod example.
Altogether noted by us in the Gulf were 225 species of copepods, 214
species in the oceanic zone, the neritic zone turning out to be significantly
poorer in species composition, with altogether 64 species being discovered in
- 21 -
it.
Only 8 species from the neritic zone were never registered in data from
oceanic stations. If suborders of copepods are taken, then in the oceanic
zone we registered 142 species of the suborder Calanidae, 61 species of suborder Cyclopidae and 11 species of Harpacticidae, in the neritic zone 33
species of Calanidae, 23 of Cyclopidae and 6 of Harpacticidae.
Altogether
out of 225 species of copepods the proportion of Calanidae was 149, of
Cyclopidae 64 and Harpacticidae 12 species.
By count Calanidae also exceeded the other two suborders: in the oceanic
zone they comprised 55% of the overall copepod count while Cyclopidae only 35%.
In the neritic zone relative content of Calanidae was even higher -- 63 7..
In the oceanic zone of the Gulf it is difficult to distinguish any sort
of mass species, as it is possible to do generally in tropical regions of
The most abundant species Clausocalanus furcatus Brady
the World Ocean.
comprises only 14% of the entire quantity of copepods of the oceanic zone,
3
its average count not exceeding 50 spec./m , however this species is not
characteristic for oceanic waters -- in the neritic zone its number is also
3
about 50 spec./m .
Among the remaining copepod species of the top 100-metre
layer it bears noting how the most frequently encountered are Calocalanus
pave Dana, C. pavoninus Farran, O. plumifera Baird, Corycella gracilis Dana.
not
At a depth below 100 metres, predominating quantitatively, thoughi fin great
number, are Pleuromamma abdominalis Lubbock, P. gracilis Claus, Lucicutia
flavicornis Claus, Haloptilus longicornis Claus.
Finally, the 200-1,000 metre
layer is characterized by such species of copepod as Eucalanus monachus Giesbrecht, E. elongatus Dana, E. attenuatus Dana, Rhincalanus cornutus Dana,
Mormonilla atlantica Wolf enden, Oncaea ornata Giesbrecht, .Conaea rapax Giesbrecht.
.
- 22 In shelf waters a number of copepod species may be regarded as of mass
proportions.
Thus, the average count of Paracalanus parvus on the shelf of
3
the Gulf of Mexico reaches considerable magnitudes -- about 300 spec./m .
Encountered in great quantities are such neritic species as P. aculeatus
Giesbrecht, P. crassirostris Dahl, Eucalanus pileatus Giesbrecht, Oithona
nana Giesbrecht, Euterpina acutifrons Dana, Dytrichoryceaus amazonicus Dahl.
At a few near-shore stations, forming a large percentage of samples were
Temora stylifera Dana and T. turbinata Dana, while in the southern part of
the Gulf (region of station 38) a few copepod species (Centropages furcatus
Dana and Acartia tonsa Dana) ran to thousands of specimens to one cubic metre. [75]
For a more detailed analysis of the link between the distribution of
copapod species and hydrological characteristics of the water area let us
return to the section running between the island of Cuba and the Dry Tortugas
islands.
At stations of this section those same species predominated in the main
that were also noted for the Gulf as a whole. Encountered in considerable
quantity were also Nannocalanus minor Claus and Oncaea media Giesbrecht. The
greatest quantity of species was in samples from station 9, the least from
station 5. In the composition of pelagic fauna of the region of station 9
we discovered along with the usual representatives of oceanic epiplankton a
number of neritic forms -- Paracalanus parvus (in great quantity), P. aculeatus,
Temora stylifera, T. turbinata, Oithona nana, Onychocoryceaus latus Dana, O.
giesbrechti Dahl, as well as neritic chaetognaths such as Sagitta hispida
Conant and S. tenuis Conant, cladoceran Podon sp.
At the remaining stations
of the cross profile we also met with a small quantity of,neritic species,
- 23 -
however not so many as at station 9 where they seemed to be concentrated.
It is most probable that neritic species were transferred into the region
of the station from the Florida shelf situated to the north.
In addition to surface oceanic and neritic species we discovered in
samples from . station 9 a series of deepwater forms, in fact right up to the
very top layer.
Work at this station was conducted in darkness; however,
species of the bathypelagic complex are here considerably more and they were
encountered in greater quantity than in samples from station 3 where we also
worked at night.
In samples from the surface 100-metre layer of station 9
such copepods emerged as Eucalanus elongatus which possesses, according to
our data, a low coefficient of intensivity of diel vertical migration,
Euchaeta media Giesbrecht, Lophothrix latipes Scott, Temeropia mayumbaensis
Scott, Lucicutia clausi Giesbrecht, Oncaea conifera Giesbrecht.
All these
species live below 200 metre and even at night rarely rise in the Gulf of
Mexico above 100 metres. Near the surface were representatives of a few
species of the genus Scolecythricella, three species of the genus Pleuromamma,
including P. xiphias Giesbrecht, which usually, according to our observations,
rise at night no higher than the 50 metre level, as well as a series of other
deepwater species, even such as do not complete a diel vertical migration.
In addition to copepods, in the very top layer deep-dwelling plankters from
other groups were found -- the siphonophors Abylopsis tetragona Otto, the
chaetognath Sagitta hexaptera d'Orbigny.
All this leads to the conclusion
that the abundance of bathypelagic species in the surface layers in the region
of station 9 is the result not only of nocturnal ascent.
In our view, it is
yet one more proof of the transport of waters onto the surface in this region.
.1i
- 24 -
We have indicated that station 82, work at which was carried out in
February 1965 during morning hours, coincided in location with station 9.
The species composition in the 0-10 metre layer of this station differed
in very few respects from the species composition of the same layer at station 9.
And here, along with epiplanktonic oceanic and neritic species were
discovered some species more characteristic of deeper layers (Neocalanus
gracilis Dana, Clausocalanus arcuicornis Dana, Haloptilus longicornis Claus),
that can hardly be explained by nocturnal migration. This fact confirms, as
we suggest, the hypothesis of the permanency of the ascent of deep lying
waters in this region.
Thus the zooplanktonic complex in the 100-metre surface layer at station [76]
9 is of mixed composition: oceanic epiplanktonic species are encountered here
along with neritic species that penetrated in here because of transport from
the Florida shelf, as well as with species from deeper layers which ascended
together with deep waters.
If we turn to the opposite end of the section, to station 1 situated in
the vicinity of the Cuban shelf then-it seems that here there are almost no
neritic species despite the proximity of this station to the shore. It is
interesting that a few of the not-so-abundant neritic species in the region
of this station were found at depths below 100 metres (Calanopia americana
Dahl, Candacia curta Dana). In the 25-50 metre layer, by comparison with
higher layers, a considerable increase in the number of surface species
(Calocalanus pavo, Undinula vulgaris Dana, Corycella gracilis) was noted.
Only in this layer were nauplius pôntellids discovered, as well as Arachnactis
sp. (larvae of Ceryantharia), i.e., organisms characteristic of hyponeuston.
This all confirms that the region of station 1 is situated in the descent zone
f
I.
-25 -
of surface waters.
Testifying to this are also the large accumulations of
algae Oscillatoria sp. at a depth lower than 200 metres. February collections at this spot (24-hour station 15), made at the same times, showed a
few changes in qualitative composition of zooplankton,
chiefly at the expense
of a number of neritic species that were not noted here in September (Oithona
nana, Sagitta hispida).
At station 5, characterized by a lesser quantity and lesser variety of
zooplankton, a clearer stratification was noticeable: the epiplanktonic
complex was silarply separated from the deep one; here hardly to be observed
at all are neither the penetration of deep-dwelling species into surface
layers nor the descent of surface species into layers deeper than 100 metres.
The last circumstance on which we should dwell is the relative abundance
in the regions of stations 3 and 9 of tunicata: appendicularia in the top
100-metre layer of both stations and Salpa in waters at station 3. A. K.
Geinrikh [1964] indicates that characteristic of regions of the World Ocean
where waters of various origins mix is an abundance of tunicata. In fact,
during the twentieth voyage of Science-Research Vessel (NIS) "Mikhail Lomonosov"
we observed in the Tasman Sea, between Australia and the northern tip of New
Zealanà, such an abundance of Salpa democratica Forsk of the selfsame species
as also in the region of station 3 in the Straits of Florida, that the remaining plankton seemed hardly noticeable against that background. This region
of the Tasman Sea is, according to A. K. Geinrikh, the division line where
tropical and subtropical waters mix.
Exactly in the same way is one fully
entitled to consider the waters of the Straits of Florida the division line
where, as we indicated, according to hydrologists, waters of the Florida
countercurrent ascend into the surface layers at station 9, having come from
tS
L
,
- 26 -
the Atlantic Ocean and mixing there with the tropical waters of the Florida
current.
Probably some ascent of waters, but of smaller scale, takes place
also in the region of station 3. In the particular conditions of our work,
it was hidden by the nocturnal ascent of deep-dwelling forms.
Thus an analysis of the qualitative distribution of zooplankton along
the section we chose, as also the features of its quantitative distribution,
tie in well with the hydrological picture of the region. This fully applies
also to the Gulf as a whole. Especially interesting in this respect is the
region of the 24-hour station 14. This station, as is to be seen from the
illustration, was executed on the eastern slope of Campeche bank to the north
of the Yucatan Channel above a height of 540 metres. Its pelagic population [77]
in many respects reminds one of the plankton at station 9 -- the same complex
system of epiplankton of the oceanic zone, of neritic species as well as bathypelagic plankters ascended into the surface layers among which the leading
place is occupied by Eucalanus monachus, E. elongatus, E. attenuatus and
Rhincalanus cornutus.
noted.
One more characteristic of this regions demands to be
In samples from the abyssal layer of 200 to 500 metres a certain
quantity of copepod species emerged characteristic for the temperate and even
northern Atlantic but not once seen by us in other regions of the Gulf of
Mexico (Microcalanus pusillus Sars, Pseudocalanus elongatus Boeck, Chiridius
armatus Boeck).
Begging to be put forward is the hypothesis that they arrive
in the south of the Gulf with the Florida countercurrent which evidently in
this region underlies the powerful stream of the Yucatan current. Hydrological
data, in particular the sharp drop in temperature of water as early as the
50-100 metre layer, confirms this hypothesis.
I
- 27 -
CONCLUSIONS
1.
The Gulf of Mexico forms part of the zone of oligotrophic waters
of the tropical Atlantic.
tropical character.
Its pelagic fauna is of a clearly expressed
Average quantity of zooplankton in the 0-100 metre
layer of the oceanic zone of the Gulf is equal to 360 spec./m
and 22 mg/m
3
by biomass; in the neritic zone, 2,850 spec./m
3
3
by count
and about
100 mg/me .
2. In tbe 100-200 metre layer of the oceanic zone the quantity of
zooplankton falls by 5-6 times by comparison with the 0-100 metre layer,
10-16 times in the 200-500 metre layer and 20-40 times in the 500-1,000
metre layer.
3. The surface 100 metre layer of the Gulf may be divided into four
zones, distinguished one from another by their zooplankton productivity:
the most productive is located exclusively on the shelf, in the others are
included both oceanic regions and also some sectors of the shelf.
4. Unevenness of distribution of zooplankton throughout the water area
of the Gulf is caused by differences in hydrological factors as between its
sectors and peculiarities of the system of currents. Neritic waters of the
Gulf of Mexico differ from oceanic both by species composition and varying
percentage ratios of basic groups of zooplankton, and also by higher development of meroplankton.
5.
In the Gulf of Mexico 225 species of copepods were registered, 214
of them in the oceanic zone.
6. The clear emergence of neritic complexes of species, as well as of
oceanic ones differing in terms of their confinement to various depths, can
be utilized as an indication of aquatic masses of various origin.
- 28 LITERATURE
I.M. Belousov, Yu,A. Ivanov, F.A. Pasternak, T.S. Rass, V.V. Rossov, 1966.
Oceanological researches of the Soviet-Cuban marine expedition. -Oceanology, 2 "Nauka" (Science),.Moscow.
D.V. Bogdanov, 1965a. Some problems of oceanographic investigations in the
tropical part of the Atlantic Ocean in connection with commercial
fisheries development. In the book: Soviet-Cuban fisheries research.
"Pishchevaya promyshlennost" (Food industry), Moscow.
[78]
D.V. Bogdanov, 1965b. Some features of the oceanography of the Mexican Gulf
and the Caribbean Sea. "Pishchevaya promyshlennost" (Food industry),
Moscow.
G.D. Vasil'ev and Yu.A. Torin, 1965. Oceanographic and industrial-biological
description of the Gulf of Mexico and the Caribbean Sea. "Pishchevaya promyshlennost" (Food Industry), Moscow.
M.E. Vinogradov, 1968. Vertical distribution of oceanic zooplankton, "Nauka"
(Science), Moscow.
A.K. Geinrykh, 1964. On the near-surface plankton of the north-eastern part
of the Pacific Ocean. In the book: Tr. of the Institute of Oceanography of the Academy of Sciences USSR, 65. "Nauka" (Science), Moscow.
Yu.A. Ivanov et al. Hydrological investigations on the. 6th, 7th and 8th voyage
of the NIS (Science-Research Vessel) "Akademik Kovalevskii". Report
on work conducted during the second half-year by the Soviet-Cuban
expedition (March-July 1965) (funds of Institute BYuM).
V.V. Zernova and Kh. Mola. 1965. Distribution of net phytoplankton in waters
of the Gulf of Mexico and Caribbean Sea, loc. cit.
I.P. Kanaeva. 1965. On the quantitative distribution of plankton of the
Atlantic Ocean. In book: Investigations in accord with the programme
of the International Geophysical Year. Tr. VNIRO. Collection 2. Moscow.
A.N. Kolesnikov, 1966. Diel migration of zooplankton in the western part of
the Gulf of Mexico. In book: Investigation of Central American seas.
Ed. 1, "Naukova Dumka" (Scientific Thoughe-- Ukrainian, translator's
note), Kiev.
A.N. Kolesnikov, 1967. Distribution of zooplankton in waters of the Tuamotu
archipelago. In book: Hydrophysical investigations of the Pacific
and Atlantic oceans during the round-the-world voyage of the NIS
(Science-Research Vessel) "Mikhail Lomonosov". Sevastopol.
d.
'
- 29 -
A.N. Kolesnikov, 1968. On the distribution of plankton in the south-west
part of the Caribbean basin. In book: Investigations of Central
American Seas, Ed. 2, "Naukova Dumka" (See above), Kiev.
A.N. Kolesnikov and A. Alfonso, 1966. Preliminary data on zooplankton of
the eastern part of the Gulf of Mexico and the Straits of Florida.
In book: Investigations of Central American seas, Ed. 1, "Naukova
Dumka" (See above), Kiev.
G.N. Mironov, 1964. A few features of the distribution of zooplankton in the
top layer of the central part of the Tyrrhenian Sea and the neighbouring part of the Balearic Sea. In book: Tr. Sevast. biol. stn.
17, Kiev.
V.K. Moryakova and A. Campos, 1966. Qualitative and quantitative characteristics
of iooplankton of the Cuban platform. In book: Investigations of
Central American seas, Ed. 1, "Naukova Dumka" (See above), Kiev.
G.G. Polikarpov, Yu.P. Zaitsev, V.P. Parchevskii, A.A. Bachurin, I.A. Sokolova,
1970. The radio-ecology of Central-American seas. In book: Marine
radioecology. "Naukova Dumka" (See above), Kiev.
V.V. Rossov, 1966. On the system of currents of Central-American seas. In
book: Investigations of Central-American seas, Ed. 1, "Naukova
Dumka" (See above), Kiev.
L.I. Sazhina, 1965. Distribution of zooplankton in the western half of the
Mediterranean Sea 1960-61. In book: Basic features of geological
structure, hydrological regime and biology of the Mediterranean
.Sea. "Nauka" (Science), Moscow.
E.V. Smirnov, N.N. Mikhailov, V.V. Rossov, 1966. Hydrochemical observations
of the Soviet-Cuban expedition. In book: Investigations of CentralAmerican seàs, Ed. 1, "Naukova Dumka" (See above), Kiev.
N.S. Khromov, 1965a. On the quantitative distribution of plankton in the
north-west part of the Caribbean Sea and the Gulf of Mexico. In
book: Tr. VNIRO, 17, Moscow.
N.S. Khromov, 1965b. Distribution of zooplankton in the Gulf of Mexico and
some features of its seasonal dynamics. In book: Soviet-Cuban
fisheries research. "Pishchevaya promyshlennost" (Food industry),
Moscow.
N.S. Khromov, 1968. Research on plankton in the Gulf of Mexico and Caribbean
Sea. In book: Soviet-Cuban fisheries research. "Pishchevaya
promyshlennost" (Food industry), Moscow.
A.A. Shmeleva, 1963. The state of the trophic base of plankton-feeding fish
in the southern Adriatic in 1958. In book: Tr. Sevast. biol. stn.
16, Kiev.
- 30 -
V.S. Shuvalov, D. Sais, A. Campos, 1965. The study of zooplankton in the
6 - 8 voyages of the NIS (Science-Research Vessel) "Akademik A.
Kovalevskii". Report on work conducted during the second half-year
of the Soviet-Cuban expedition (March-July, 1965) (Funds of InBYuM)..
V.A. Yashnov, 1961. Vertical distribution of the zooplankton mass of the
tropical region of the Atlantic Ocean. Reportsr Academy of
Sciences, USSR, 136, 3.
B a n n e r A. H. 1951. The Mysidacea and Euphausiacea.- Gulf of Mexico, its Origin,
Waters and Marine Life.- Fishery Bulletin. 59. 'Washington.
G r i c e G. D. 1960. Copepods of the genus Oithona frorn the Gulf of ,Niexico.- Bull.
cf biar. Sci. Gulf. 10.
Al o o r e I-1. B. 1954. The Zooplanktcn of the Gulf of Mexico.- Gulf of .^iexico, its
Origin Waters and Marine Life. rishery f3ulIetin, 89. Washington.
P i e r c e E. L. 195-t. Notes of *.e Cractacmathes of the Gull of Aiexico.- Ibidem.
S c h m i t t W. L. 1954. The Copepods.- 1 hidem.
S e a r s Al. 1954. The Hydromedusaes and Siphonophores of the Gulf of Atexico.Ibidem.
S u a r e z C a a b r o I. 1935. informe pretiminar sobre im•esticliaciones en plancton
de los mares Cubanos.- Contribucion 10 (lei centro de investigaciones pesqueras.
S u a r e z C a a b r o 1. 195•1. Quetognates de los mares Cubanos.-.Niemorias de la
soci::dadcubana de historia nxtural, 22, 2.
T o k i o lc a T. 1955. Notes en some Chaetohnatha from the Gulf of i%iexico.- Bull.
of Dlar. Sel. Gulf, 5.
T o k i o k a T. y S u a r e z C a a b r o 1. 1956. Appendicularias de los mares cubanos.-Mem. de la soc. cub. de hist., 23, 1.
SOME FEATURES OF ZOOPLANKTON DISTRIBUTION
IN THE GULI° OF MFXICO
A. N. KOLESNIKOV
Surnmary
The article deals with the generalized data on distribution of zooplinkton in the Gulf
of üexico. obtained as a result of prncessin<, th:: data of the Soviet-Cubian expedition in i96•^1965. The Gulf Of Mexico is ir.cluded into the zone of oli;,fotroniiic Waters of thè tropic part
of the V I,uitic O:ean. Tha acern,,^e aric,unt nf zoor.tankton in a Îaver of 0-900 ni of the OceaIIIc zone in the ,^ulf equals to 360 speC,m'' iri nnrnber ilnd 22 mzr/ril3 in hlUn123ss, the average
In ; laver
amount of zo01) lcir,kton in the nuritic 7onc is 23-i0 sl•eclrnl' and abuui 100
of 100-200 m of the oceanic zone the amnunt of zooP:ani<ton is 5-6 times In .: Îaver of 200500 rn-10--•16 times, in a layer of 500-I0r!0 ni -`_'i)--tJ times as low as in the layer of
0--100 in. The surface 100-rneter laver of the :!;if mav he divided into four znnes different
in ahundanca of znoplankton. A close relation is observed in the -ulf hetween the quantitative
and qualitntive distribution of zoo^^lan:;ton and In•drolo^ic:rl peculiarities of its diiferent
parts. Neritic^a•aters of the golf diifer from the oceanic ones in buth specific composition and
different per,=nta,,e ratio of zoopl.,ni<ton basic ^Irroups as.tvell as in more intensive development of rnernplankton. In tire Gulf of Mexico out of 225 species of copepods'11-1 are found in
oceanic waters and only 6;- in rreritic unes.
V.V. hossov ana ^. Santana, 1966. Hydrological investigations
of the boviet-Cuban expedition. In Book: Investigations
of Central ÉLrnerican seas. .1,Ad. 1. "Naukovo Dtmlma" (see
^
above), Kieva