2. THE HISTORY OF HYDROBIOLOGICAL INVESTIGATIONS

Many countries have been carrying out hydrobiological investigations in the Barents Sea and the Kara Sea. The results of many Norwegian, English, German, and other scientific cruises are published in English and are accessible to the scientists of many countries, whereas the papers of Russian scientists have been are published mainly in Russian, which makes them almost inaccessible to English readers. This section references papers of Russian scientists, giving special emphasis to the description of the annual cycle of plankton, which could serve as a basis for synthesis of hydrobiological data quality control criteria. All publications cited in this section are presented in references.

2.1 Phytoplankton

Barents Sea

The study of Barents Sea phytoplankton started in the 1870's (Palibin, 1903-1906; Deryugin, 1915; Linko, 1907). Only factual material without any detailed analysis was accumulated during this first stage that came to an end by 1910.

At that time, scientists from Austria, England, Belgium, Germany, Denmark, Norway, and Sweden also began carrying out hydrobiological observations in the Barents Sea. During this stage 300-500 stations were sampled.

The early 20th century was characterized mostly by scientists studying the phytoplankton of the Barents Sea (Manteifel, 1938; Mosentsova, 1939; Schultz, Wulf, 1929). At that time a great volume of data on species composition and distribution allowed for the first theoretical conclusions (Kiselev, 1928; Usachev, 1935). These papers resulted in a list of species of Arctic phytoplankton giving details of its taxonomic content. Studies were performed mostly by scientists of the Institute of the Northern Studies (Russia). Later the leadership transferred to the Polar Institute of Fisheries and Oceanography (PINRO). During that period, data from 20 expeditions (nearly 800 stations) were collected.

Valuable work begun in 1950-1960 by M. Roukhiyainen initiated the systematic study of phytoplankton at MMBI. Her papers (Roukhiyainen, 1956, 1960, 1961a, 1962b, 1967) considered and discussed taxonomic composition, spatial distribution, dynamics of seasonal variability (the succession system) of phytoplankton communities and the coastal waters of the Kola Peninsula. Of extreme importance was that Roukhiyainen's study resulted in the compilation of the most complete taxonomic list of the Barents Sea phytoplankton (Roukhiyainen, 1966a), and revealed general ecological mechanisms of the vertical distribution of the pelagic marine algae (Roukhiyainen, 1966b).

Among all the other scientific papers published during the 1950's-1960's, emphasis should be given to the papers of N. Kashkin (1963, 1964) on the ecology and biogeography of several algae species, of G. Barashkov (1962) on the biochemical composition of phytoplankton cells, and of M. Kamshilov (1950) on the spatial distribution of several diatom species. The papers of A. Solovieva and her colleagues (Solovieva, 1973, 1975, 1976; Sokolova, Solovieva, 1971; Vedernikov, Solovieva, 1972; Sokolova, 1972; Solovieva, Churbanova, 1980) published in the 1970's considered a wide range of problems on taxonomic composition, primary production, chlorophyll concentration, and the dynamics and spatial distribution of phytoplankton. In 1970-1980, a number of papers of Ryzhov gave high priority to the seasonal and geographic groups of phytoplankton, the effect of frontal zones on phytoplankton distribution, and on using phytoplankton species as bioindicators of various water masses in the Barents Sea (Ryzhov, 1976, 1985, 1986; Ryzhov, Syuzeva, 1974; Ryzhov et al, 1987).

In 1950-1980, more than 2,000 stations were sampled during 100 scientific cruises. In the second half of the 1980's another generation of hydrobiologists started their work in the MMBI, and opened a new stage of the Barents Sea phytoplankton study. Their investigations were focused on the examination of phytoplankton taxonomic composition (Larionov, 1995; Makarevich, 1996, 1997; Makarevich, Larionov, 1992; Druzhkov, Makarevich, 1999), spatial structure ( Druzhkov, Makarevich, 1989, 1996; Larionov, 1992, 1993, 1997), productivity characteristics of phytoplankton ( Bobrov, 1985; Kuznetsov et al., 1994; Savinov, 1997), the succession system, and the seasonal effect on phytocenosis (Druzhkov, Makarevich, 1991; Druzhkov, Makarevich., 1996).

In the 1990's, the attention of scientists was focused mostly on the nearshore waters of Novaya Zemlya, Franz-Josef Land, Spitsbergen, and St. Ann Trough in the Arctic Ocean, Pechora and Kara Seas. Most of these regions had never been examined before. Cruises of nuclear icebreakers from the Barents to Kara Sea and back during winter allowed for the collection of phytoplankton data in ice covered regions.

During the 1990's, investigations of Barents Sea phytoplankton were carried out by the Polar Institute of Fisheries and Oceanology, Murmansk, the Institute of Oceanology, Moscow, the Botanical Institute, St. Petersburg, and the Murmansk Hydrometeorological Service.

From the 1980's untill the present, more than 100 scientific cruises were carried out, collecting about 3,000 samples. In addition to almost all the Arctic Seas, the region of investigation covers the Norwegian Sea, the North Sea, and the White Sea, with thorough study of individual fjords and bays of both the Barents Sea and the Kara Sea. In Dal'nezelenskaya Bay multi-year complex ecological monitoring was carried out ( Druzhkov et al., 1990).

A list of publications of the Barents Sea phytoplankton and the stages of phytoplankton study of the Barents Sea by Russian scientists are presented in the "Review by region" and "History references" sections.

Kara Sea

The history of phytoplankton studies of the Kara Sea started from the scientific cruise of A. Nordensheld in 1875. The Kara Sea is distinguished by severe weather conditions. It is covered with ice for 8-9 months, and as a result during 1900-1980 the number of scientific cruises did not exceed several dozens. The Arctic scientific cruise of Moscow State University (MSU), conducted in 1974 focused on microflora of the northwest Kara Sea and resulted in 25 stations and 148 samples.

The present stage of studies, started in 1980, is focused on large-scale examinations of the Kara Sea phytoplankton. During this time the plankton studies are analyzing more aspects, expanding the territory of examination, and adding data from more years and seasons. The use of nuclear icebreakers for scientific purposes makes it possible to conduct scientific cruises in inaccessible regions of the Kara Sea in winter and spring. Examination of this region is conducted mainly by the MMBI ( Bobrov et al., 1989, Makarevich, 1993, 1994, 1995). Scientific work in the Kara Sea was also carried out by the Institute of Oceanology, Moscow (Vedernikov et al., 1994), the Arctic and Antarctic Research Institute, St. Petersburg, and some other institutions. About 20 scientific cruises, providing 1,200 samples, have already been conducted during this period. The major portion of this material is used in the present review.

2.2 Zooplankton

Barents Sea

The history of study of the Barents Sea zooplankton started with the Murmansk Scientific and Fisheries Expedition organized by N. Knipovich in 1898. The expedition functioned effectively until World War I (1914) and had accumulated annual material characterizing the zooplankton community development in different regions of the Barents Sea (mostly in its coastal zone and in the Kola Bay). The results obtained during that series of investigations were presented in monographs by Linko (1907) and Deryugin (1915). Zooplankton studies performed during the expeditions were targeted at forecasting for fishermen, giving them information when "bait fish" were approaching the coast (mostly capelin were used as a "bait fish" during fishing of cod). The same data were used for forecasting migrations of white whale following shoals of cod along the coastline. There were 15-20 expeditions with zooplankton data, with 300-500 samples collected.

The next stage in the study of the Barents Sea zooplankton was targeted at providing data on the herring fishery (1930-1950). During this period, quantitative methods for collection and analysis of plankton were developed (Bogorov, 1927, 1933, 1934, 1938a, b, 1939a, b, 1940a), and an observation network for the Barents Sea was developed. The paper of Manteifel (1941) can be considered as an encyclopedia of zooplankton study in the Barents Sea during that period.

In 1950, scheduled (annual) sampling of zooplankton was launched using standard methods and stations. Since 1953, the data on abundance of euphausiid crustaceans was collected (Drobysheva, 1979, 1988, 1994; Drobysheva, Nesterova, 1996). Since 1959, the material on zooplankton was accumulated (Degtereva, 1979; Degtereva, Nesterova, 1985; Nesterova, 1990). Samples of euphausiids were taken in winter, and sampling of mesozooplankton was done twice a year (April-May, May-June). During the same period (1953-1959), a program of more detailed examination of zooplankton in the coastal zone of Murmansk (Kamshylov et al., 1958; Zelikman, Kamshylov, 1960; Zelikman, 1977) as well as in the southwest Barents Sea (Zelikman, 1961a, 1966; Myaemets, Veldre, 1964) was conducted. The focus was on the seasonal dynamics of plankton, the effect of "predator-prey" relationships, inter-year and intra-year variability in zooplankton abundance, and the biology of dominant species of zooplankton (Kamshylov, 1951, 1952, 1955, 1958a, b; Zelikman, 1958a, b, 1961a, b, c, 1964; Petrovskaya, 1960; Rzhepishevsky, 1958a, b, 1960a, b). During this period, 60 to 80 expeditions were carried out and 3,000 to 4,000 zooplankton samples were collected.

In the history of Barents Sea zooplankton studies, the years, from 1960-1990 were valuable for providing information on food stocks for the larvae and juveniles of dominant commercial fishes ( Antipova et al., 1974; Degtereva, 1979; Degtereva, Nesterova, 1985; Nesterova, 1990). Moreover, data on zooplankton, very important for the capelin fishery forecast, were collected (Degtereva et al., 1990). In 1982-1993, the zooplankton state was examined annually in the Central Barents Sea ( Tereshchcenko et al., 1994), where similar surveys had not been previously performed.

In 1976-1984, scientists of the MMBI recommenced studies on the seasonal dynamics of zooplankton (Fomin, 1978, 1991; Fomin, Chirkova, 1988; Druzhkov, Fomin, 1991), the life cycle of Calanus finmarchicus (Fomin, 1995), and euphausiid crustaceans (Timofeev, 1996a).

In the 1980's, samples of zooplankton were collected in the Kola Bay during environmental monitoring by the Murmansk Regional Hydrometeorological Service ( Glukhov et al., 1992).

The number of expeditions during the period 1950-1990 were 90-100, with 10,000-15,000 samples collected.

In the history of investigations of the Barents Sea zooplankton, the 1990's are characterized, by large-scale sampling of zooplankton, and also by enhanced southeast Barents Sea monitoring ( Timofeev, 1992a; Timofeev, Shirokolobova, 1996; Makarevich, Druzhinina, 1997; Stogov, Antsulevich, 1995, 1996). The latter was associated with the detection of oil deposits in the Pechora Sea. Previously, as a result of the navaga fishery, zooplankton was studied in that region by the Arkhangel branch of the Polar Institute of Fishery and Oceanology ( Chuksina, 1971; Zalesskikh, 1986, 1990). During the same period, the MMBI continued investigations of zooplankton in the Kola Bay and the Motovsky Bay (Ilin et al., 1992; Timofeev, Shirokobolova, 1993; Druzhinina, 1997; Timofeev, 1997a, 1998a). Valuable data on zooplankton were provided by 1,000-2,000 samples collected during approximately 20 cruises.

Zooplankton studies were started in the 1990's by Norwegian scientists who primarily examined the fjords of the northern Norway, mostly in Balsfjord (Hopkins, 1981). During 1980-1990, studies of zooplankton were moved to the central Barents Sea and focused mostly on two projects (1984-1989, PRO MARE; 1990-1994, MARE NOR). Their results were published in the materials of some symposia (Sakshaug et al., 1991; Skjoldal et al., 1995). Again, the study of zooplankton, both in Norway and Russia, was associated with the capelin and herring fishery.

Most of the data collected during 1950-1998 are generalized and presented in "Review by Region" and "History references" sections.

Norwegian scientists published on the topics:

• Zooplankton biomass dynamics in the central Barents Sea during 1979-1984 ( Rey et al., 1987);
• Dynamics of the abundance of pelagic hyperiids during 1982-1993 ( Dalpadado et al., 1994);
• Dynamics of abundance of the euphausiid crustaceans during 1982-1993 ( Dalpadado and Skjoldal, 1995).

Kara Sea

The first information on the Kara Sea zooplankton was presented in the reports of scientific and fisheries expeditions: the Russian Polar cruise of 1900-1903, and the Marine Polar cruise of 1910-1915 (Linko, 1908, 1913; Milekovsky, 1970; Evgenov, Kupetsky, 1985). The papers of that period emphasized studies on zooplankton species composition, and the biogeographical and ecological characteristics of dominant species. Almost 100 plankton samples were collected during these scientific cruises.

In 1920-1940, zooplankton sampling was carried out during most cruises, examining both the Kara Sea and the Laptev Sea. Zooplankton distribution and abundance was estimated, and the possibility of using zooplankton as an indicator of water masses of different origins was illustrated (Rossolimo, 1927; Jashnov, 1927, 1940; Bernshtein, 1931, 1934; Khmyznikova, 1931, 1935, 1936 a,b, 1946: Bogorov, 1945; Ponomareva, 1949, 1957). In 1920-1940, 10 to 15 cruises examining zooplankton collected nearly 1,000 samples.

In 1950-1970, zooplankton of the open Kara Sea was poorly examined. Studies were conducted only in the fjord of the Ob Gulf, the Yenisey Bay and some other nearshore Kara Sea waters ( Greze, 1957; Leshchinskaya, 1962; Leleko, 1985; Pirozhnikov, 1985; Chislenko, 1972a, b). Of the most interest were the results of seasonal observations on zooplankton carried out in the Yenisey Bay and the Dixon Bay (Chislenko, 1972 a, b).

In 1981 and 1982, the MMBI conducted two scientific cruises (300 samples total) in the southwestern Kara Sea. Information on zooplankton biomass distribution became available. Zooplankton biomass distribution was considered as a function of water column hydrological structure. Data on the distribution and abundance of dominant species were collected, and characteristics of the life cycles of some species were analyzed ( Timofeev, 1983, 1985, 1989a, 1990a, 1995; Fomin et al., 1984; Fomin, Petrov, 1985; Fomin, 1989a; Zubova, 1990).

In 1990, an intensive study in the southwestern Kara Sea was launched, induced by exploration of oil and natural gas stocks detected in that region. The zooplankton study was conducted within the framework of complex ecological monitoring of the Kara Sea ecosystem and made available some new information on distribution, abundance, and biomass of zooplankton, and on the life cycles of the dominant species ( Novoselov 1993; Vinogradov et al., 1994 a, b; Vinogradov, 1995; Scientific Report, 1996; Vozzhynskaya et al., 1997; Druzhinina, 1998). In all, 10 scientific cruises on zooplankton studies were conducted and about 300 samples were collected.

Calanus finmarchicus in the Barents Sea

A. Linko was the first Russian scientist to investigate the Barents Sea. He summarized plankton samples collected during the Murmansk scientific and commercial cruises during 1898-1906 (headed by Knipovich and Breitfus), and presented them in a monograph (Linko, 1907). Linko established that C. finmarchicus, a dominant species in the Barents Sea zooplankton, and could be used as an indicator of the waters of Atlantic origin. He pointed out that the vertical distribution of C. finmarchicus in the nearshore zones and open sea was determined by the water column vertical structure. These crustaceans were observed in the Barents Sea in a temperature range of +1.8 to +10.6 ^oC and salinity range of 32.12 to 35.08 pss.

Taxonomic analysis

V. Jaschnov (1939a) established that the region north of 75^oN was inhabited by an endemic population of C. finmarchicus, unrelated genetically to the population dwelling in the southern Barents Sea. This conclusion stimulated to do more precize morphological studies. In 1955, V. Yashnov published his review on Calanus systematics, which described a new species, C. glacialis, distinct from C. finmarchicus. In the late 1950's, Yashnov ( 1955, 1957, 1958) published a set of papers scrutinizing basic aspects of the morphology, distribution, and systematics of Calanus finmarchicus s.l.

Brodsky (1959, 1967 , 1972) continued the morphological studies. He used more features than Jaschnov and drew the conclusion that C. finmarchicus and C. glacialis could not be considered as a separate species. He assumed that both were subspecies of the same species existing under various ecological conditions. Brodsky (1972) supposed that the complicated group of C. finmarchicus s.l. was in the stage of "incomplete species formation". By the early 1980's, after publication of Frost's paper (Frost, 1974), Jaschnov's viewpoint became dominant and thus, both C. finmarchicus and C. glacialis were considered as "good species". These ideas were published in the latest monograph of K. Brodsky (Brodsky et al., 1983), where C. finmarchicus, C. glacialis, and C. marshallae were termed as "sibling species".

It should be mentioned that accurate species identification for C. finmarchicus and C. glacialis is still a serious problem, especially in the regions of joint occurrance of both species. The species were determined by size criteria ( Mumm, 1991) or by using the concept termed "mixed population" developed Vinogradov et al., (1995, 1996).

Despite the existing problems, it is important to give an accurate species identification for both C. finmarchicus and C. glacialis, otherwise there exists a risk of erroneous conclusions on the tendency of zooplankton community variation. For example, S. Novoselov (1993) made a comparison between zooplankton of the fjord Baidaratskaya Guba (the Kara Sea) for different time periods: 1945-1946 and 1991. The presence of a large number of C. glacialis in samples of 1991 and their absence in the samples of 1945-1946 ( Ponomareva 1957) allowed for the conclusion that cooling of the Arctic seas had caused substantial changes in zooplankton fauna. This assumption was based on the knowledge that C. glacialis related to Arctic species. The conclusion of S. Novoselov on the Arctic cooling in the early 1990's was in contradiction with the real situation as exactly during that period the Arctic warming occurred (Carmack et al., 1997; Morison et al., 1998). This contradiction can be explained by an assumption that S. Novoselov did not take into account the fact that in 1945-1946 C. glacialis was not distinguished from composite species C. finmarchicus s.l.

Distribution

Until the 1950's, when V.Jaschnov (1955, 1957, 1958) demonstrated the composite character of the superspecies, C. finmarchicus s.l., Calanus was identified as oceanic, open sea species widely distributed in the waters of the Northern Hemisphere (Brodsky 1950). After some revisions of the superspecies, the area of C. finmarchicus itself had been reduced sufficiently, and at present Calanus is usually considered as a boreal North Atlantic species abundant as well in the waters of the west Arctic basin, where C. finmarchicus is a good indicator of Atlantic waters (Jaschnov 1955, 1958, 1961, 1966; Abramova 1956; Kashkin 1962; Sushkina 1962; Brodsky 1965; Brodsky et al., 1983).

Biomass, abundance, production

Jaschnov (1939b) determined that 84% of plankton biomass in the southwest Barents Sea consists of Calanus. The average biomass of C. finmarchicus comprised 24 ton/km²; with a minimum biomass value (8.5 ton/km²) in March and April, and a maximum in August. V. Yashnov estimated the annual production of C. finmarchicus to be 65 ton/km², and from the data of the PINRO (1950-1970) the crustacean production comprised 77.5 ton/km² ( Degtereva, Nesterova, 1985).

In the nearshore waters, the impact of Calanus on zooplankton biomass comprises 60-64% (Manteifel, 1939; Fomin, 1978, 1995) and during some years its impact can decrease to 13-34% (Kamshilov et al., 1958). Seasonal dynamics of C. finmarchicus biomass in the nearshore Barents Sea is characterized by the presence of one maximum that usually occurs in June and July (Kamshilov et al., 1958; Zelikman, Kamshilov, 1960; Fomin, 1978, 1995). The annual production of C. finmarchicus in the coastal zone is less than in the west Barents Sea and comprises 277.3 mg/m³ (Kamshilov 1958a).

Since the late 1950's the PINRO has been conducting annual spring and summer cruises during which the information on zooplankton, mostly of the western Barents Sea, is collected (Degtereva, 1979; Degtereva, Nesterova, 1989; Degtereva et al., 1990). Data on the number of eggs, nauplii, and copepodite stages of C. finmarchicus were presented at two transects conducted in 1959-1983 at North Cape - the Bear Island and the Kola Meridian section. The relationship between the number of Calanus nauplii and water temperature in spring was determined as follows:

Y = 774.6

X - 2035.2,

in which: Y is nauplii abundance in the Murman drift in the layer of 0-50 m (individuals/m ³); X is temperature in the Murman drift in the layer of 0-50m (^oC).

Life cycle

The first information on the life cycle of C. finmarchicus of the Barents Sea was obtained by Bogorov (1932, 1939b), Manteifel (1939, 1941), and Jaschnov (1939a). As a result, the C. finmarchicus life cycle can be presented as follows:

• During winter C. finmarchicus is at depth and concentrated in streams of the Nordkapp drift;
• In late March, C. finmarchicus rises to surface;
• April-May is a period of reproduction, starting mostly in the southwest and then distributing gradually to the east and northeast. Spawned specimens descend to deeper water layers, where they die or are used as a food by predators;
• In July-September, as a result of a water temperature rise in the upper layers (up to 6-7^oC), C. finmarchicus descends to near-bottom layers. During this period it stops growing and changes its color (red becomes yellow and white). Starting from the second half of August, C. finmarchicus initiate their diurnal vertical migrations;
• In October-November C. finmarchicus is concentrated in deep-water parts of the Barents Sea and gradually stops its diurnal vertical migrations.

Such a life cycle suggests that over most of the Barents Sea, C. finmarchicus is monocyclic but during some years the second generation of C. finmarchicus comes from the West (specimens hatched in nearshore northwest Norwegian waters). The young of this generation do not spread farther East than 33^o30' E. Appearance of C. finmarchicus specimens of the second generation in the southwest Barents Sea (Manteifel, 1939, 1941) can be explained by the ocean warming observed in the 1930's ( Fu et al.,1999).

In the 1950's, a study of the C. finmarchicus life cycle was conducted in the nearshore Barents Sea at a longitude of 36^oE. It resulted in a conclusion on the bicyclic character of Calanus life cycle in that region: specimens of the spring generation lived about three months and specimens of summer and fall generations lived about 9 months (Kamshylov, 1952, 1955; Nesmelova, 1966). The study performed in 1964 did not confirm that conclusion (Nesmelova 1968). In 1976-1977, the next run of experiments justified the biocyclic character of Calanus life cycle (Fomin, 1978, 1995). In the latter case, spring reproduction of C. finmarchicus was established to be more extended in time and more intensive, whereas fall reproduction was relatively short-term and not intensive (Fomin, 1978, 1995). The study resulted in the conclusion that a monocyclic Calanus life cycle existed during cold years, and bicyclic Calanus life cycle existed during warm years (Zelikman, 1982). Moreover, a conclusion was made that the changes in reproduction of Barents Sea C. finmarchicus had resulted from variations of the annual temperature regime (Degtereva 1971, 1973, 1979; Degtereva et al., 1990). M. Kamshylov (1955) had determined fertility of C. finmarchicus females: potential fertility was 2,000 eggs per female, the observed was between 1,000 and 1,500 eggs.

References

The literature list of research on the zooplankton of the Barents Sea is presented in the references. The papers on distribution, biology, and ecology of euphausiid crustaceans are not included, as reviews on these crustaceans are presented in the papers of Drobysheva (1994) and Timofeev (1996a).

 

2.3 Zoobenthos

S. Denisenko, Zoological Institute, S. Petersburg

Brief Historical Note (Barents Sea)

The initiation of Barents Sea benthos studies date back to the second half of 18th century, when Ozeretskovsky (1804) began gathering collections of marine animals in nearshore Murman waters. The systematic study of species composition and distribution of the bottom invertebrates started in the Barents Sea with the intensification of the fisheries in the last quarter of the 19th century. The study was focused on the effect of various environmental factors on the distribution of organisms.

The results of commercial and biological endeavors headed by Knipovich served as the scientific basis for the use of bioresources of the Barents Sea and the adjacent North Atlantic regions (Knipovich, 1902, 1904). For the first time, the collected zoological data provided valuable information for biogeographical zoning and showed the increase of the Atlantic origin species in the Kola Bay in 1893-1908 (Deryugin, 1915).

By 1915, more than 3,000 benthos stations were sampled, two thirds of these during Russian expeditions (Galkin, 1979).

In the period 1920-1925, a hypothesis on the possibility of shifting zoobenthic biogeographic boundaries in the Barents Sea, as a result of marine environment temperature, was verified ( Tanasiichuk, 1927; Shorygin, 1928).

Since 1924, besides quantitative sampling equipment, grabs have been used for benthic studies, the methods for quantitative accounting of the bottom fauna have been refined, which allowed for comprehensive and detailed benthic surveys of the Barents Sea in the 1920's-1930's. A result of these surveys was the identification of patterns of the distribution of some zoobenthic taxonomic groups and the zoobenthic community (Brotskaya, Zenkevich, 1939; Filatova, 1938).

From 1921-1940, benthos collections were conducted at 5,000 stations, of which 4,800 were made by Russian investigators (Galkin, 1979). Figure 1 depicts the locations of data from 2,700 benthic stations collected in the period 1920-1940.

In the second half of the 1940's, thanks to the efforts of the PINRO and the Murman Biological Station (MBS), wide-scale benthos investigations were restored. The collected material made it possible to study littoral and sublittoral zone communities of the south and southeast Barents Sea, to determine patterns in the distribution of important taxonomic groups, and to analyze zoobenthos trophic structure as a whole (Kuznetsov, Matveeva, 1948; Turpaeva, 1948; Pergament, 1957; Zatsepin, 1962; Galkin, 1964; Zatsepin, Rittikh, 1968a, 1968b; Kuznetsov, 1970).

The samples of the bottom fauna collected in the 1940's-1950's along the Kola Meridian transect, served as a basis for the analysis of the bottom fauna multi-year fluctuations in that region (Nesis, 1960).

Since the early 1960's the "scuba diving method" of hydrobiological studies has been developed in Russia. This method was used for investigation of the bottom ecosystems of the upper sublittoral zone in the fjords and bays of the Murman region, the Frants-Josef Land and the Nonaya Zemlya areas ( Propp, 1966; Pushkin, 1968; Shelf Biocenosis, 1977; Golikov, Averintsev, 1977). During the same years the ecosystem approach in the zoobenthos investigations was targeted at the communities of the littoral zone, which made it possible to study not only the ecosystem structure but functionality. (Streltsov et al., 1974).

In 1968-1970, during a short time period and using one standard method. PINRO conducted a total survey of the Barents Sea, which revealed a substantial decrease in zoobenthos biomass in comparison with the 1920's-1930's (Antipova, 1975).

On the whole, in the period 1945-1977, data from about 4,000 benthic stations were collected in the Barents Sea (Galkin 1979), of which approximately 3,400 stations were collected by Russian investigators.

In the 1980's, underwater photographic surveys and benthos collections were widely used by Russian geological institutions for conducting landscape and ecological shelf investigations ( Gurevich, Kazakov, 1989). Today the total number of benthic stations conducted with these methods is about several thousand. These data have limited utility due to the lack of detailed metadata. Simultaneously with photo surveys, the gathering of collections was usually conducted at stations using the same gear for both animals and sediments. The quality of photographs was only good for recognizing megabenthos and large-scale forms of macrobenthic epifauna.

The use of traditional methods of benthos collection with the combination of advanced underwater imaging techniques made it possible for the MMBI and the Zoological Institute (St. Petersburg) to study in detail the structure and functioning of the bottom ecosystems in the fjords of the Murman waters (Zhukov, 1988; Semenov, 1991; Golikov et al., 1993; Hydrobiological Study, 1994).

Zoobenthos investigations were jointly carried out by MMBI and PINRO, searching for and identifying populations of commercially important invertebrates (mostly crustaceans, mollusks, and echinoderms). In the 1970's and 1980's, the results of these studies served as a basis for the rational use of northern shrimps and Icelandic scallops in the Barents Sea (Bryazgin, 1981; Denisenko, 1988; Denisenko, Bliznichenko, 1989; Berenboim, 1992).

Along with the scientific and commercial study of some species, traditional investigations of zoobenthos was continued. However it was mostly targeted at detailed information on the background state of marine biota in the regions planned for intensification of economic activity or the regions under ecological protection (Averintsev, 1993; Luppova et al., 1993; Denisenko et al., 1995; Denisenko et al., 1997). These studies were mostly conducted by expeditions of the MMBI, organized in cooperation with international scientists. During recent years, some attempts were made to restore regular observations along the Kola Meridian transect ( Denisenko, 1999).

During 1978-1999, the number of benthic stations sampled, excluding underwater surveys, was 2,000. The processing of the data collected during these expeditions has not been finalized, and as a result their analysis is far from complete.

Zoobenthos as an indicator of climate change

Many investigators believe that the macrozoobenthos is a good indicator of the environmental multi-year fluctuations, as most of the bottom animals are characterized by a sedentary mode of life and a long life cycle. One can consider Deryugin (1915) as the initiator of studies on multi-year fluctuations of the Barents Sea bottom fauna. In 1908-1909, in the Kola Bay, he detected several species unusual for that fjord. He related this phenomena to the fluctuation of the water temperature ( Deryugin, 1924).

Based on various zoobenthic taxonomic groups, Shorygin (1928), Tanaisiichuk (1927), Cheremisina (1948) et al. substantiated the possibility of shifting biogeographic boundaries in the Barents Sea as a result of temperature fluctuations. Gurianova (1947) related the occurrence of some Atlantic and Arctic species in the White Sea to multi-year hydrological fluctuations in the northeast Atlantic. Balker (1957, 1965) concluded that the benthos might react to Arctic seas warming or cooling with a lag time depending on the particular species. This was also confirmed by Nesis (1960), who analyzed multi-year fluctuations of boreal and Arctic species along the Kolsky Meridian as a function of hydrological regime. Galkin ( 1964, 1984, 1998) presented multi-year variations of mollusks as a function of the temperature regime.

The monitoring of the benthic community of the Barents Sea showed that some boreal species can react to environmental changes (Cheremisina 1948; Nesis, 1960). This is due to variations in the population size at the habitat boundaries, not because of changes in the sizes and shapes of the habitats. (Galkin, 1998).

Besides the analysis of zoobenthos biogeographic composition for studies of climatic tendency, there are some other effective and easily standardized methods that allow for accurate determination of temperature paleoreconstructions (Zolotarev, 1989). Many marine animals have massive carbonate formations, which act as a recording structure. As with tree rings and fish scales, these carbonate formations record seasonal growth patterns (Clark, 1974). Analysis of the recording structure allow for descriptions of environmental conditions.

A great number of long-lived benthic animals dwell in the Arctic seas; clams such as Arctica islandica, Serripes groenlandicus; horse mussel Modiolus modiolus; sea urchins of the genus Strongylocentrotus; brittle stars (Ophiuroidea); barnacles of the genus Balanus, and other animals that can live several dozens of years. Multiple samples of these dominant species collected in the Barents Sea during the last several centuries are present in the scientific institutions of Russia and other countries. Analysis of recording structures can be used for the documentation of climatic trends.

Problems of estimation of zoobenthos fluctuations

The analysis of fluctuations in zoobenthos functional characteristics is usually based on the results of quantitative collection techniques. In faunistic and biogeographic investigations, the use of these data is often hindered because the archive lists of species are frequently less comprehensive than present ones, as a result of the limited capabilities of the older sampling equipment, the greater experience of modern taxonomists, and the progressive development of taxonomy. Comparability of qualitative lists, despite their incompleteness, is often more effective as they present mostly large sized dominant forms, easily collected with simple sampling equipment. In addition, the probability of catching rare animals with the use of these tools is greater, as a result of covering more surface area for their collection. Key attention should be focused on these specimens as they can be good indicators of both warming and cooling (Zenkevich, 1963).

Some problems in the estimation of zoobenthos fluctuations result from navigational errors and poor-quality collecting, washing, sorting, and storing procedures of the benthic samples. The errors in determination of the ship location without any control via sextant, for system of satellite navigation or system of radiolights during 2-3 days could be up to 20-30 miles. Thus a 20-30 mile deviation in localization of one or another population or community can result from navigational errors.

In the analysis of possible fluctuations of the Barents Sea bottom fauna resulting from climatic or other reasons, it is necessary to take into account the elements of collection and processing of benthic samples. These elements should be formalized and included in the data description report.

References

The list of papers on the Barents Sea zoobenthos are presented in references.