CANADIAN TRANSLATION OF FISHERIES AND AQUATIC SCIENCES

No. 4917

Some patterns in the life of the plankton of the central Arctic basin

by E.A. Pavshtiks

Original Title: 0 nekotorykh zakonomernostyakh v zhizni planktona tsentral'nogo arkticheskogo basseina

From: Biol. Tsentral'nogo Arkticheskogo Basseina, p. 142-154, 1980

Translated by the Translation Bureau Multilingual Services Division Department of the Secretary of State of Canada

Department of Fisheries and Oceans Arctic Biological Station Ste. Anne de Bellevue, P.Q.

1983

27 pages typescript 1 • 'DEPARTMENT OF THE SECRETAR) OR STATE SECRÉTARIAT D'ÉTAT TRANSLATION BUREAU BUREAU DES TRADUCTIONS

MULTILINGUAL SERVICES DIVISION DES SERVICES DIVISION MULTILINGUES crF■ts •?•?t7

TRANSLATED rROM - TRADuCTION DE - Eh Rus Sian English

AUTMOR - AUTEUR Pavshtiks, E.A.

TITLE IN LNGLISN - TITRE ANGLAIS Sabine patterns in the life of the plankton of the central Arctic basin

TIYI.L IN PORElée. LANGUAGE ITIPAN.5..I 7 E5II - I RC ••,1 URSI 'TITRE Eh LAhGut [TrANGERE CPANI:P PI E. NDmA.hs 0 nekotorykh zakonomernostyakh y zhizni planktona tsentral'nogo arkticheskogo basseina

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SOME PATTERNS IN THE LIFE OF THE PLANKTON OF THE CENTRAL ARCTIC BASIN by U.D.C. 577.472(26)577.475 E.A. Pavshtiks Since the drift of Nansen's "Prama", when the first plankton collections were made in the high latitudes of the Arctic (Sars, 1900), our knowledge of the specific composition of the plankton and of its conditions of habitation has been 142 greatly augmented. Samplings taken from the submarines "Nautilus" (Hardy et al., 1936) and "Seadragon" (Grice, 1962), as well as from the drifting station NP-1 (Shirshov, 1938, 1944) and the icebreaker "Sedov" (Bogorov, 1946) yielded valuable information not only with respect to the specific composition of the fauna of the pelagic zone of the Arctic Basin, but also as regards the biology of prolific species of . Studies were made of seasonal variations in the age composition of populations, the distinctive character of the vertical distribution of the plankton, the penetration of the Central Arctic Basin by Pacific species/ and other questions. Nevertheless, the findings were clearly inadeauate for purposes of solving a number of zoogeographic problems (Virketis, 1946). This was because the systematiCs and of the species of arctic zooplankton lacked clarity, which was later introduced by the investigations of Brodskii (1950, 1959) and Virketis (1957, 1959). Even when arrangements were being made for the regular study of the life in the pelagic zone of the Central Arétic Basin, resolving the problem of plankton productivity was considered the first-priority task. Virketis (1946) 143 in summarising the results of the 25 years of research on the plankton in the Arctic, wrote about the need for studying the interrelationship between organisms, food chains and the cycle of matter in the sea. Such studies began with the commen- cement of regular observations at the "North Pole" drifting stations of the Arctic and Antarctic Scientific Research Institute (AANII). Material and methodology. Forming the basis of this study were plankton samplings obtained in the fifties, sixties and seventies by hydrologists of AANII, acting on instructions from the Zoological Institute of the USSR Academy of Sciences. A total of 1638 samples of zooplankton were collected at 257 stations, the positions of which are shown in fig. 1. " Pee. 1. éxema pacnonmenlin nnairxioirnwx cranunit

1 - cn-1, 1937 r.. 2 - n/n 'Cano, 1937-1939 rr., 3 - CII-2 - 195d-1957 rr., 4 - C11-16, cn-17, cn-19, C1-1-201 1968-1974 rr. • •

Fig. 1. Siting of the plankton stations 1 - NP-1, 1937; 2 - icebreaker "Sedov", 1937-1939;

3 - NP-2 - NP-7, 1950-1957; 4 - NP-16&17, NP-19, NP - 20, 1968-1974.

The plankton was collected by Nansen nets (diameter 50 •cm, No. 23 silk mesh) and Juday nets (diameter 37 cm, No. 38 silk mesh). The catches were effected with closing nets. Arctic demersal, Atlantic, intermediate and arctic surficial 144 water masses were seined successively.

The material collected was fixed in ethyl alcohol and in part, in 5% formalin. Processing of the samples was done under stationary conditions at the Zoological Institute of the USSR Academy of Sciences in accordance with the standard procedure (Yashnov, 1934; Bogorov, 1957).

Results and discussion The fauna of the pelagic zone of the central part of the Arctic Basin has been described in a number of publi- cations (Dogorov, 1946; Brodskii and Nikitin, 1955; Virketis, 1946, 1957; Barnard, 1959; Grainger, 1965; Johnson, 1963; Minoda, 1967 et al.). The most detailed studies were those of the . An investigation was begun into the life cycle of the dominant organisms in the plankton (Boaorov, 1946; Pavshtikr;, 1976, 1977; Minoda, 1967). By virtue of year- round observations of the status and development of the plankton on NP-2-NP-7, NP-16, NP-17, NP-19 and NP-20, information on its biomass was obtained. This information was used in compiling a map of the biomass of the seston in the 0-50 m layer during the growing season for eventual incorporation in the Atlas of -Ehe Arctic (Brodskii and Pavshtiks, 1976). The data provide evidence of the fact that during the polar day, beneath the old pack ice in the central part of the Arctic Basin the life is fairly rich in the upper layers of the igater*mass. Constituting the seston, besides detritus, are units of the Medusa (for example, Aeginopsis laurentii), Amphipoda (Gammaridae, Hyperiidae), Chaetognatha (juv.), pelagic shrimps (Decapoda) and pteropod molluscs (Pteropoda: Limacina helicina, Clione limacina), Calanoida .r*

7 ( hyperboreus, C. glacialis, Metridia longa, Pareuchaeta norvegica, P. glacialis, Microcalanus pygmaeus) and others. The maximum biomass of the zooDlankton in the 0-50 m layer is normally observed in July, when C. hvperboreus are numerous there. Underwater prominences (ridges, banks, and shoals) are conducive to vertical intermixing of waters, enrichment of the upper layers with biogenic substanues, and consequently, the development of the and of the zooplankton feeding upon it. Some increase in the biomass of the seston during the period July to September is observed in the vicinities of elf. Lomonosov and Mendeleev underwater ridges, and also northwards of the New Siberian Islands and Vrangel Island. During the period July to September between 50 and . 90% of the zooplankton is concentrated near the surface in the 0-25 m layer. During the polar day the biomass of the 3 seston above the Lomonosov Ridge reaches 200-500 mg/m,. Patches of high seston biomass (up to 1000 mg/m 3 ) are found in the east, northwards of Vrangel Island, where modified Atlantic waters occur together with those of Pacific origin. Thus, despite the fact that the plankton population in the centre of the Arctic Basin is much lower than it is in moderate latitudes, in summer the biomass of the plankton 145 near the surface is the same as that in the Greenland Sea during winter and early spring. This is because in the Arctic Basin the large Calanidae (, Pareuchaeta glacialis), amphipods, pteropod mollusks, chaetognaths, appendicularians and other living at great depths further south, inhabit the upper layers of the water. Johnson (1963), citina the findings of drifting station "Alpha", noted that juvenile stages of Metridia longa are present in the plankton throughout a fairly long period and that during the polar night, P. glacialis and P. polaris lay eggs that have rich yolks long before the appearance of the phytomlankton. Apparently these carnivorous have access to food even during the winter, while C. hyperboreus and C. glacialis retain a large Quantity of high caloric fat, which enables them to live without food for a long time in winter. The permanent zooplankton population in the centre of the Arctic Basin is relatively small, which is due to the low productivity of the phytoplankton even during the light period of spring and summer, and to the absence of meroplankton. The attribute of the vast majority of the arctic and abyssal benthic invertebrates to lay vitelline eggs and develop without passing through a larval stage is well known. Thorson (1936) noted that in the open sea to the east of Greenland only 5% of the benthic invertebrates have pelagic larvae. The abundance (population) of the plankton (specimens/ m3 ) changes most noticeably from season to seapon in the 0 - 250 m layer. In the spring and summer, alternating in time, almost all (up to 90%) of the plankton organisms migrate to this layer in order to feed and reproduce. And this despite the - fact that near the surface the water temperature beneath the ice hardly changes during the year, remaining very low at all times (to -1.8°). In the autumn and winter the plankton is pelagically dispersed in layers where the temperature is above 0 °C (close to interlayers of Atlantic

waters and in the modified Atlantic waters) (fig. 2). In the Atlantic interlayer, seasonal variations in the quantity of plankton at depths of 500 - 700 m are less pronounced, while in the benthic layer they are not noticeable at all. Geinrikh(1961, p. 71) states that "The biological season must be considered to be that segment of the annual cycle of a community which is differentiated from the other segments by a group of seasonal species, present in the active state, and by a group of year-round species, possessing at this time an annual maximum of abundancc." In the central part of the Arctic Basin, beneath old pack ice, where to all intents and purposes only the illuminance changes, there are nevertheless, seasonal variations in the specific composition and abundance of the plankton. In a number of ragions the biomass of the seston varies little from season to season, since amphipods that reproduce under the ice in winter arrive to take the place of minute copepods which are more numerous in summer. A A I I III • 1 I'1 2> VI YE ZIT 17 .71 1174 11 • . A "/ eli)9V4 // • e-e /.!•ef -

;L? ••■••'-•

/ /*".. • / / e/ • // • • • , /e bol • / / // • ..•••••• •e• ••• •• ••• Y//j/ /•/' k „ ,•/•

, . 750 -I . ,.--,..../,. r,,I.,,,A

F/.-/I •••"/."» - // //e. .• ....,/./ /.,/ / .e.' •••////

. t "•■,/f//, i'le ege:!: -.• 6./ ,...i ri712

ki• 'bottom H C. glacialis (E) patioHe Cepeplioro no- Pitc. 2. Bepraxanbaoe pacnpenenexue Calanus hyPerboreus (A) remeakte rona (% otnnerà %mom oco6elk) (no Ilanurraxc, 1976, 1977] moo& • 1-0; 2 - 1.-5; 3- 5-10; 4- 1O-20;5 -20-50; 6 - >SO •

Fig. 2. Vertical distribution of (A) Calanus hyperboreus and (B) C. glacialis in the vicinitTST-EHe North Pole in the course of a year (%age of total number of individuals) (after Pavshtiks, 1976, 1977)

According to observations made on drifting station

NP-17, in the summer, close to the North Pole, the following large were fairly abundant in the Makarov Trough: Parathemisto libellula, Calanus hyperboreus, PareuchaeLa

.glacialis, Metridia longa and others, greatly surpassing the

biomass of the zooplankton. In the winter of 1968-69, NP - 17 drifted in the vicinity of the Nansen Trough, where at that time there were also many of the amphipods Rozinante fragilis, Gammarus wilkitzkii, Eusirus holmi, Pseudolibtotus glacialis, 1 P. nanseni, and others beneath the ice. The young of these fairly large representatives of the cryofauna greatly - exceeded the biomass of the seston.

Throughout the year the biomass of the seston was also high in the eastern sector of the Arctic Basin, in the region of drift of NP-20. Replacing the copepods, the abundance of which is high beneath the ice in summer, minute juveniles of the amphipods Apherusa glacialis, Gammarus wilkitzkii, Pseuda- librotus nanseni and others, appear in the plankton near the surface in the winter. Apparently the cryofauna enters the central part of the Arctic Basin from the peripheral shelf seas. For example, the amphipod Rozinante fragilis, which was found at many of the plankton stations executed by the drifting station NP-17 and which normally colonises the shallow, eastern region of the Arctic, was also found in the western sector of the Arctic Basin (Gur'yanova, 1951, 1962). Close to the North Pole the amphipod Eusirus holmi was discovered. This amphipod had previously been found in the northern regions of the Kara, Laptev and Eastern Siberian Seas. Gammarus witkitzkii also reaches the North Pole with the ice floes.

The Pacific amphipod Orchonella pacifica was caught with a

1The Amphipoda were determined as to species by E.F. Gur'yanova and N.L. Tsvetkova. JO_

lift net in a hole on NP-17. According to Gur'yanova's data (1962), this amphipod was well known in the Sea of - Japan and the Sea of Okhobsk, is from the region of the

Kurile Islands and is not even indicated in the centre of the Arctic Basin. Thus, the biomass of the seston in the arctic surface waters increases in the summer on account of repro- duction of the Calanoida and in part, because of the presence of juveniles of Parathemisto libellula and certain other Hvperiidae. In winter, when the Calanoida migrate from the surface into warmer, deeper layers of the water, the Amphipoda (cryofauna) reproduce beneath the ice. In getting caught in

the plankton nets, at times the tiny juveniles of these amphi- pods greatly increase the biomass of the seston. The food supply of the plankton and the cryofauna evidently consists of the phytoplankton and the algae devoloping in the water beneath the ice and on the lower surfaces of the floes.

In June, only individual cells of Coscinodiscus sp., and Melosira arctica are found in the net catches. In July, besides Coscinodiscus and Melosira, various Chaetoceras and Rhizosolenia species appear. In the vicinity of the North

Pole the phytoplankton is observed to be at a peak in August (Usachev, 1961). In winter the phytoplankton is not to be seen in net samplings. It has been established (Shirshov, 1938) that the development of phytoplankton is limited first and foremost 148 - by - the amount of solar light penetrating beneath the ice once July comes and the snow cover on the floes diminishes. Although the water temperature in the central part of the Arctic Basin is constantly low and does not vary with the seasons, by July the abundance of the organisms beneath the ice increases approximately tenfold in comparison with that 3 in the dark period, averaging as much as 200 specimens/m in the vicinity of the North Pole (Pavshtiks, 1971a). Moreover, in the 50-250 m layer the plankton population rarely exceeds 50 specimens/m 3 , and deeper still, in the Atlantic interlayer, 3 19 specimens/m . Especially ntimerous here are the copepods Oithona similis and Microcalanus pygmaeus. The abundance of Calanus hyperboreus and is lower, but they were present in the plankton during all the seasons at all of the stations executed and are frequently dominant in the biomass (Bogorov, 1946; Pavshtiks, 1971 a, b, 1977; Minoda, 1967). In the course of the year the relative abundance 2 plankton organisms varies markedly in the centre of certain of the Arctic Basin (Pavshtiks, 1971a). In January-February the proportion of Metridia longa in the 0-250 m layer increases to 13%, and that of the Chaetognatha to 4.4%. Between early

2 The relative abundance is the share (%) of a particular organism in the total number of organisms in a particular layer of water. March and the end of May Oithona similis is numerically dominant in the plankton (56-67%). In June the relative abundance of Calanus glacialis increases (to 12.5%), as does that of Calanus hyperboreus (to 10.4% in Augus-0. Also numerous in August are Oikopleura juv., and Fritillaria borealis (20%). In October Microcalanus pygmaeus constitutes 51.5% of the population. The ecosystem of the pelagic zone of the central regions of the Arctic Basin exists under extreme conditions. The very short growina season, the limited food resources over the greater part of the year, the low temperatures of the upper layer of water beneath the ice, which remain unchanged the year round, and the long polar night, all these factors limit the development of plankton. Damkaer (1975) considers that the ability of photosynthesis to take place beneath the ice at a very low illuminance and the capacity of many marine invertebrates to produce young in the winter are partial adaptations which have stabilised and will not progress any further. These adaptations, however as the author points out, can be regarded as stages in the direction of an expansion of both the producing period and the capabilities for resource utilisation during a large part of the year. of Besides the phytoplankton, the growing season,,which is much shorter in the vicinity of the North Pole than it is in the moderatB latitudes and which has a low productivity, another potential food source for plankton organisms is the detritus brought to the Arctic Basin by waters of Atlantic and Pacific origin, and by the waters of shallow northern seas. Our findings indicate that the digestive tracts of C. hyperboreus and C. glacialis are filled with detritus. /5.

Only part of the C. hyperboreus population reproduces annually. In February and March sexually mature individuals ascend to the 50 - 200 m layer, which is also where their spawning apparently takes place. Copedites of stages 1 and 2 normally appear in the plankton in May, but not until August does their abundance increase in the surface layer. By October a part of the stage 2 copedites are passing into stage 3, although individual stage 2 cope- dites can be found in the plankton even as late as February. In winter, stage 3 copepodites are more numerous than stage 2, stage 4 than stage 3, and stage 5 than stage 4. It would seem that the copepodites can remain in the 4th and 5th stages of development for less than one year, living at depths in the 250 to 1000 m range (and perhaps even deeper). Judging from the age composition of the population, only part of the stage 5 copepodites migrate to the surface during the second year of life, moult, mature and reproduce. Probably, the other part of them is converted into males and females only in the third spring after birth. In the waters of the cold Greenland current the life span of C. hyperboreus is not less than two years and not all of its females participate annually in reproduction (Ussing, 1938). Over a large part of the year C. glacialis, in contrast to C. hyperboreus, lives in the 50 - 200 m layer, although isolated individuals of it are able to migrate into deeper layers (see fig. 2). In the high arctic latitudes, copepodites of the 4th, 5th and 6th stages are dominant in the C. glacialis population year-round, although even in this species the age composition of the population changes somewhat in the year (fig. 3). From January through April, females are dominant in the 0 - 250 m layer. From April to May the percentage of sexually mature individuals in the population decreases sharply. It is probably at this time that their spawning occurs and the spawned out individuals die. Although young copepodites (stages 1 and 2) of C. glacialis appear in May and June, there are few of them in the plankton samples and they develop slowly at the prevailing low temperature. It is not until October that the percentage of stage 3 copepodites increases in the C. glacialis population. Delayed development of and C. glacialis at the prevailing low water temperature was repeatedly observed under natural conditions (Grainger, 1965; Hardy et al., 1936; Marshall and Orr, 1955; Wiborg, 1955 et al.) and has been proved experimentally (Matthews, 1966). In October C. glacialis migrates from the cold arctic surfacé waters to the warm Atlantic interlayer at a depth of 250 - 500 m (temperature .gradient about 2 °C). Due to the insufficiency of food in the ecosystem of the pelagic zone 'of the Arctic Basin, in the course of their evolution, in C. hyperboreus and C. glacialis life cycles developed in which their population maxima are separated in space and time. C. hyperboreus is an interzonal species and can be found at any depth, whereas C. glacialis spends the greater part of the year in an intemediate laver at the boundary of the Atlantic interlayer, where it lives at temperatures close to 0°C, as is the case in the deeps of the Norwegian Sea (Ostvedt' 1955). The third Calanoida species dominating in the ecosystem of the pelagic zone of the Arctic Basin - Metridia

more longa - is ewidely distributed and present in the plankton the vear-round, although it is less abundant than C. hyperboreus M. longa is capable of migrating over long distances. In winter, individuals of it in the 4th, 5th and 6th copedite stages are found at great depths. In the upper layers of the water mass, sexually mature individuals within the M. longa population dominate from May through August. Its reproductive period is protracted in time. Juveniles (cope- dites stages 1 and 2) are present in the 0-250 m layer from July until March of the following year, but the population peak of the copepodites in stages 1 and 2 is observable only in August and September. Judging from the age composition of the population in the central part of the Arctic Basin, M. longa lives for at least 2 years with one part of its popu- lation evidently reproducing at the beginning of the polar summer and the other, closer to winter (Bogorov, 1946; Pavshtiks, 1977). 111111111

. • • . . I ' ffJZT2FY illf Elf .17. .7:11 • . Akre./

Pic. 3. Boapacraol cobras nowyninit Calanoida a cam 250-0 as paioie Ceacpuoro nomoca a ?antenna. road 4— çalanus hyperbortus; H — C. glacialis; B Metridia 1onga; — .Microcalonus pyisnœests. Ha pic. Um:sitter I—III manna Konenoawron /1

Fig. 3. Age composition of Calanoida populations in the 0 - 250 m layer in the vicinity of the North Pole during the year A - Calanus hyperboreus; B - C. glacialis;'C - Metridia longa; D - Microcalonus pygmaeus. In fig. 131 includes copepodites of stages 1, 2 and 3.

The most numerousHoflthe Calanoida is the minute Microcalanus pygmaeus. Although it has not proved possible to detect the population peak of the young of this species, it is evident from an analysis of the age composition of the population that its reproductive period coincides with the light period in the high latitudes, that is, it extends over almost half a year. Bogorov (1946) found that the population peak of copepodites of stagesl and 2 of M. pygmaeus falls in August, coinciding with the maximum development of the phytoplankton in these latitudes. The life cycle is appro- ximately the same in Oithona similis (Cyclopoida). It is nature that in the central part of the Arctic Basin the Calanidae reproduce during the polar day: the period of maximum development of the phytoplankton. The reproduction of these plankton-dominating crustaceans, however, is protracted in time and for the greater part of the year thev - live in different water masses. The first to reproduce in the layer of intermediate arctic waters is the large C. hvperboreus. This takes place in February and and March at depths Of betwcen 50 and 200 m. Its nauplii and copepodites develop much more slowly than is the case ;10

in other species. Migrating behind it into this layer is C. glacialis, which reproduces here from April until the - end of June.

Due to the insufficiency of food in the Arctic, in the course of their evolution, in C. glacialis and C. hyperboreus life cycles developed in which their population peaks occur at different times. In C. glacialis the yearly maxima of population and biomass are observed in June (its nauplii develop more rapidly than those of C. hyperboreus), and the corresponding maxima of C. hyperboreus, in August and September.

Over the greater part of the year these two 152 species live at different depths: C. glacialis in the 50 - 200 m layer, while C. hyperboreus is dispersed throughout the entire water mass down to and including the maximum depths (see fig. 2). M. 12nm, also has a peak population of juveniles in July, although its copepodites in stages 1, 2 and 3 can be discovered in the plankton as late as March of the following year. In winter, according to our findings, C. hyperboreus, longa and M. pygmaeus are scattered throughout the entire water mass and even occur at depths exceeding 1000 m. The vertical migrations of these crastaceans, their migration to great depths and continuous presence there 1 evidently aid in the preservation of their populations in the harsh conditions of the Central Arctic Basin. Having overwintered in the deeps, in the spring they initiate a small new local population by reproducing near the surface in arctic waters at a tempeature of -1.6 °C. It is well known that the cold Eastern Greenland current carries ice floes from the region of the North Pole into the Greenland Sea. Together with the waters of this current a part of the populations of C. hyperboreus, glacialis, M. lonqa and M. pygmaeus can reenter the C. Greenland and Norwegian Seas by way of the Arctic Basin and initiate large new populations under the more favourable conditions obtaining in the regions where the warm and cold waters meet (the "polar front") (Pavshtiks, 1960, 1971). The ecosystem of the pelagic zone cf the central part of the Arctic Basin is closely linked with the ecosystems of its peripheral northern seas, from which elements of the fauna are constantly being added fo it. The adaptation cf the latter to the conditions of life at great depths in comparatively warm Atlantic waters enables them to exist for a long time. The Atlantic and Pacific bathy,pelagic Copepoda are capable, together with the currents, of surmounting submarine elevations (for example the Lomonosov Ridge) and of disseminating through the water area of the Arctic Basin. '‘). Usually, sexually immature individuals of the prolific bathy_pelagic species penetrate the Basin, but only a small number of them survive. Our observations indicated that Pacific species penetrate as far as the western sector of the Amerasian sub-basin, which conforms to the dissemination in this basin of the waters of Pacific origin (Rusanov, 1980). We did not discover these species in the Nansen and Amundsen Troughs. In comparing the pelagic ecosystem of the Arctic Basin with that of the pelagic zone of Antarctica (Voronina, 1976), we detected numerous common traits and patterns: 1 - the shortness of the vegetative period and of

the reproductive peak of prolific species; 2 - the connection between the period of reproduction and fattening of the young and the period of maximum development of the phytoplankton; 3 - the monocyclical character of the principal prolific species; 4 - the low specialisation of prolific species, their wide feeding spectra and low specific diversity; 5 - the relative simplicity of the trophic chain. References 1. Bogorov, V.G. The zooplankton from samplings made by the expedition on the icebreaker "Sedov",during the period 1937— 1939. IN: Transactions of the drifting expedition of the Chief Directorate of the Northern Sea Route on the icebreaker "Sedov", 1937 - 1940. Leningrad, Glavsevmorput (C.D. of the Northern Sea Route), 1946, Vol. 3, pp. 336-370. 2. Ibid. Standardisation of marine plankton research. - Transactions of the Institute of Oceanology, USSR Acad. of Sciences, 1957, Vol. 24, pp. 200-215. 3. Brodskii, K.A., The Copepods (Calanoida) of the farieastern seas of the USSR and the Polar Basin - In: Keys for determining the fauna of the USSR Academy of Sciences, 1950, No. 35. 4. Ibid. Fauna of the Copepoda (Calanoida) and the zoogeographic zoning of the northern part of the Pacific Ocean and adjacent waters. Moscow and Leningrad, Publishing house of the USSR Academy of Sciences, 222 pp. 5. Brodskii, K.A., and Nikitin, M.M. Hydrobiological studies. - In: Results of observations on a scientific research driftina station in 1950 and 1951. Leningrad, Morskoi Transport (Sea Transport), 1955, Vol. 1, pp. 411-465.

6. Brodskii, K.A., and Pavshtiks, E.A. Plankton of the central part of the Arctic Basin. - Vopr. geografii (Questions in Geography), 1976, collection 101, pp. 148-167. 7. Virketis, M.A. Plankton rescarch in the Arctic over a 25-year period. - Problemy Arktiki, 1946, No. 3, pp. 39-54. 8. Virketis,.M.A. Some data on the zooplankton of the central part of the Arctic Basin. - In: "Results of observations on the scientific research drifting stations "North Pole 3" and "North Pole 4", 1954/ 1955. Leningrad, 1957, Vol. 1, pp. 238-342. 9. Ibid. Information relating to the zooplankton of the central part of the Arctic Basin. - In: Results of the scientific research activities of drifting stations NP-4 and NP-5 in 1955 and 1956. Leningrad, Morskoi Transport, 1959, Vol. 2, 'pp. 133-338. 10. Voronina, N.M. Pelagic ecosystems of the Southern Ocean. - In: The 3rd Congress of therm-Union Hydro- biological society. Abstracts of reports, 1976, Vol. 1, pp. 63-64. 11. Genrikh, A.K. Seasonal phenomena in the plankton of the world ocean. 1. Seasonal phenomena in middle and high latitudes. - Transactions of the Institute of Oceanology, USSR Academy of Sciences, 1961. Vol 51, pp. 57-81.

12. Guryanova, E.F. Amphipods of the seas of the USSR. Moscow and Leningrad, Publishing House of the USSR Acad. of Sciences, 1951, 1032 pp. 13. Ibid. Amphipods of the northern part of the Pacific Ocean. Moscow, Publishing house of the USSR Acad. of Sciences, 1962, 442 pp. 14. Pavshtiks, E.A. Basic patterns in the development of the plankton in the Norwegian and Greenland Seas. - In: Soviet fisheries research in the seas of the European North, 1960, pp. 151-163. 15. Ibid. Seasonal variations in the zoomlankton population in the vicinity of the North Pole. - Dokl. AN SSSR, 1971a, Vol. 196, No. 2, pp. 441-444 16. Ibid. A hydrobiological description of the waters of the Arctic Basin in the region of drift station "North Pole - 17." - Transactions of the Arctic and Antarctic Scientific Research Institute, 1971b, Vol. 302, pp. 63-69. 17. Ibid. Biological seasons and life span of Calanus hvperboreus Kroyet in the centre of the Arctic. - In: The nature and economy of the North, 1976, No. 4, pp. 121-127. 18. Ibid. Seasonal variations of the age composition of Calanoida populations in the Arctic Basin. - In: Studies of the fauna of the seas. Leningrad, "Nauka," (Science) 1977. Vol. 19 (27), pp. 56-72. 19. Rusanov, V.P. A hydrochemical description of the surface waters of the Arctic Basin. - In: The biology of the Central Arctic Basin, Moscow, "Nauka", 1980. 2,5 20. Usachev, P.I. The Phytoplankton near the North Pole: from the samplings by P.P. Shirshov on the first drifting station "North Pole" in 1937 - 1938 urder the leadership of I.D. Papanin. - Transactions of theAll-Union Hydro- biological Society, 1961, Vol. 11, pp. 189-208. 21. Shirshov, P.P. Oceanological observations. - Dokl. ANSSSR, 1938, Vol. 1 9, No. 8. 22. Ibid. Scientific results of the drift of station "North Pole". General conference of the USSR Acad. of Sciences held 14-17 February 1944. Moscow and Leningrad, 1944, 128 pp. 23. Yashnov, V.A. Instructions concerning the sammling and processing of plankton. Moscow, VNIRO .g1-Union Research Institute of Sea Fisheries and Oceanography), 1934, pp. 1-44. ?..(a

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1 .5oropon Br. 3oreentu•ret no ceopum ammenotom na n/n 'Conon' 1037- 1939 rr. ce B nu.; Tm»: opegdonnumg ezonensurao rnapcenuorams n/u 'Cenon'. 1937-1040. 11.: rpaacentappnyru. 1946. T. 3. c. 333- 370. • *BoroPoss.r,Oraunaproparout smparoxsotaurromaraz siconanoneutat. - Tp. oneanon. AH °CCP, 1957, T. 24, c. 200-215. - 3 .Epotomià K.A. Becn000ron pavai ealanoidi) nansaenoesonmax baôpen ccœ flonnpuoro 6acontoa. B Onpenezorreemt no :baya. CCCP. M.; fi.: A 1133-30 AH CCCP, 1950, )4: 35. •Epoucont K.ft. •ayna Peano:toms pastoon (Calannida) i nooreorPà4wiecKoe • pallounimanxe canope:à natfra 11:noro :mana I conpenemaugx zoo. M.; ' 114 Itaa-no AH CCCP, 1957. 222 c. '•51:oucton K.A. Hus:issu M.M. rampes:mol-tome:ose patIcyrbi. B int.: Ma- «manu na6mentenoll narino•atoomozonarnmesoll npeRescutea c-ramoro1950/ • 51 r. E.: Mopcooli "paionopr. 1955, e. 1, c. 411-465. 5 .5poncoog K.A., Ennuie:toc flmourson neirspammit naos): Aparsonecato- ro 6aconlina. Bonp. reorpae«, 1976, c6. 101, c. .148-167. # •Bmpoesoc M.A. finaux-roman noonenonanog o Apmute as 2Q atm Epo6ne- sua Apnr• ono, 1946, Nt 3, c. 39-.54. 3.Bit px :no c M.A. Henoropme.spounoe o poonmoursone nerspanboon «en: Apyro- «matoro 6accelna. - B zH.t Marepetatua ita6nezettal tutynno-accnenorarrenb- citsxneit'xientx arent0111 .C.esepubilt I1omoo-3' x 'Oenaposal nomoo-4' 1954/1955 r. 1957, e. 1, c. 238.-342. !•Bapiesoc M.A. Masepsamo no noonmoursony uenspanbnol'neterst Aparronocato- ro 6aooelna. B Pesynp•errta Haynno-oocnettobasenbcxxx pa6os ope:t- g:7mm CT&I1XIC11-4 x C11-5 1955/56 r. 114 Plopciol Tpamenopp, 1959, „ .s. 2, c. 133-339. 1 %opoonna H.M. Ilenarosecnue outocmcsema 10notPro mea«. B menu 8C0003. ntnpo6non. Tep.. AMI., 1976, s..1, c. 63-64. • -Lee topoX A.K. CO3OUlible 111330Wis a nnaurrone Moponoro oxonua. 1.. Cepoo- Hein nrasensto p UneUULTOtie cpcmon a IbiODJUIX suopos. Tp. Ho-Pra oneanon. • , •AH CCCP,1961, T. 51, c. 57-81.. -I-n000sa E.43. 601101230bbl bepell CCCP• M4 .11.1 kbn-abo AH CCCP. „ 1051..1032 c. ' •L iTypbnuona &nonnes:a onnepuot Itacro Timor° oxeana. M.: Han-ao „ AH CCCP, 1962. 442 C. • aln•rnIte B.A. Ocnonme nap000mepuocro pana:mus rulaussona n Hopnenc- =ou x rpelotauncoo:. Moposx...• B one Ceoescxxe pu6oxpastic-sneomae oc- cnononansut n smpox EaponeACooro anticipa, 1960, c. 151-163, 15n aSUITillt E.A. O canOttlikan waraeocomax «ortenstocsu amonnanyrona D po:4 oxe Cepepooro notima. - Bonn. AH CCCP, 1971a, T. 196, nbm. 2,. C. 441..444. . 1611aDuzemcc E.A. rompo600norstiecoas: mipisserecsinte nos Apernuecnore 6ac- Cet« n panoue ope114ot csantom 'Ce:sep:De Tp. Avars.; Ansapne. Hartoaccnen. sawra, 19716, T. 302, c. 63-69. tus c B.A. 'Boonoronecone 00303bl • 1711a3 itp=onnarranbuocsb :guano . Ca la nus hyperboreus KaSyer lampe Aposoms... B mita Ilimana II tonteerne Ce-- , Dom 1976, man. 4, c. 121-127. igflanurrxxo B.A. C.330333.10 113140133132 363pacornoro cocsana nœrynanot :mono- *or« pannon Calanoida s Aprrosecoom 6accenne. - B no.; liccnenonauxo L9 '4taysibt, sue& 11.: Horta, 1977, 19(27), c. 56-72. o• 13.11. roppomporwraniat Itapavrepicsoua nonepruocmax non Ararro-

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