by Boris SIRENKO, Head of the Laboratory of Marine Studies, RAS Zoological Institute (St. Petersburg), Sergei GAGAEV, Cand. Sc. (Biol), senior research assistant of the same laboratory

Studies carried out by a team of research divers from the RAS Zoological Institute during the 52nd and 54th Russian Antarctic Expeditions (2006-2008, 2008-2010) formed a basis for hydrobiological monitoring in the Prydz Bay of the Sea of Commonwealth. Studies of biocenoses at the depths of 3 to 43 m resulted in collection of about 600 species of bottom plants and animals from the coastal water of the sixth continent and revealed peculiarities of spreading of the flora and fauna in this region.

Regions of diving expeditions carried out by the RAS Zoological Institute in 1965-2009 (red points).

A BIT OF HISTORY

Russian diving studies in the Antarctic Regions started in the middle of the 20th century. During the summer of 1965-1966, a team headed by Mikhail Propp (Murmansk Marine Biological Institute, USSR Academy of Sciences) and including Alexander Pushkin (the same Institute) and Yevgeny Gruzov (Zoological Institute) carried out more than 160 diving sessions in the coastal waters near the Mirny Station. Abundant flora and fauna were discovered under the two-meter ice at a depth of up to 50 m by specialists.

The results proved to be so important and interesting that a year later the hydrobiological team was again included in the Soviet Antarctic Expedition. It was headed by Yevgeny Gruzov and included Alexander Pushkin (diver), Valentin Lyuleyev and Sergei Rybakov (specialists in underwater equipment). The research was carried out on the South Shetland Islands, Peter I Island, and areas of water near Molodyozhnaya, Mirny, and Novolazarevskaya stations.

In the expedition of 1970-1972 the studies were continued by a team including Yevgeny Gruzov, Yuri Giginyak, Alexander Sheremetevsky, Valentin Lyuleyev, Sergei Rybakov, and Vladimir Andronnikov. The courage of all these specialists is remarkable: they were among the pioneers of studies of the Antarctic submarine world.

These studies were then unfortunately discontinued: during the three decades that followed our efforts were concentrated on submarine studies in the Russian seas of Arctic Regions and the Far East. And only in the middle of the first decade of the 21st century could we resume the diving hydrobiological research in the Antarctic Regions. Scientists of the Zoological Institute--the authors of this paper and Vladislav Dzhurinsky-realized this possibility during the season of 2006-2007 near the Progress Station. And during the season of 2008-2009 our colleagues Vladislav Potin, Fyodor Kobekov, and Pavel Ignatov managed to complete the creation of bases of biological monitoring system in the Prydz Bay.

GOLIKOV'S METHOD

Changes in the climate and augmenting anthropogenic effects on the biota during recent years critically necessitate monitoring of the environment. In order to properly organize its biological constituent, we should study the initial state of the communities in the ecosystem.

Why is this monitoring so important even in the Antarctic Regions, where human intervention in the nature is yet insignificant? To be sure, the ecosystems of these regions are very far from large industrial centers. Their composition and distribution of the flora and fauna suffer virtually no anthropogenic effects, but are mainly determined by natural factors. However, such situation can alter in the near future.

Officially the territory of the Antarctic Regions is not yet divided between the countries of the world, but some of them have already put claims on some of its sectors. The number of the countries which have for the first time organized stations on the ice continent increased over recent years, while the countries which had built their stations long before are now actively expanding their presence. For example, Chile is constructing an airport and a sea port, the Chinese are building three-storeyed houses, ports, roads, etc. at their bases. The number of specialists present on the continent is

increasing with every year. In order to evaluate the impact of human activities on the nature of this region in future, we should know the present-day initial state of sea ecosystems, not yet affected by these activities. The importance of these studies is explained by vital economic needs: search for new food resources implies the knowledge of the composition and distribution of economically important vertebrates and fishes.

The unique studies carried out by our scientists in the Antarctic Regions are based on the method developed by a well-known Russian hydrobiologist, Dr. Sc. (Biol.), Alexander Golikov (in 1966-1992 he headed our laboratory). His method is based on collection of the benthos* with consideration for the size of organisms and pattern of their distribution and subsequent complex analysis of the flora and fauna species composition and quantitative distribution of hydrobionts in the sections. The meio-benthos (animals smaller than 1 mm) are collected with a special measuring glass. The macrobenthos (animals and plants bigger than 1 mm) are collected in a different way: using 0.1 m² frame and a scoop (from solid soil) and a diver's bottom scooper (from soft soil). The fauna and flora with scanty or uneven distribution are estimated in 1 m frames and from a certain area swimming by with a one-meter rod along a measuring halyard located at the bottom and collecting all rare animals not captured before by 0.1 and 1.0 m² frames. Phyto-and zooplankton are collected in plankton nets, pulling them from bottom to surface.

As a rule, prior to taking samples, the typical areas of the bottom in the studied region are photographed for preliminary evaluation of distribution of biocenoses, for fixing of their boundaries, and choice of the best areas for subsequent collection of samples. Every diving is directly followed by a brief report of the diver in front of the videocam.

After collection of macrobenthos samples, they are washed from silt and sand. Their laboratory processing is carried out at the Progress station (including sorting of

* Benthos is a sum of microorganisms inhabiting the soil and bottom soil of water bodies. The sea benthos serves as food for many fishes and other sea animals and is used by humans (for example, algae, oysters, crabs).--Ed.

the samples by animal groups, primary identification, estimation of their number and mass of predominating species, as well as fixing of the samples in formalin and ethanol for further preservation at the Zoological Institute).

As we have already mentioned, a region in the Prydz Bay of the Sea of Commonwealth in the eastern part of Antarctica was chosen for monitoring. This area is located around an oasis--a land part, which is free of ice and snow in summer. The Russian Progress, Chinese, and seasonal Australian stations are situated there. The majority of sections have been carried out near Nell's fjord, at sites differing bionomially, and a lesser part-near Chinese and Russian stations. The construction of the port by the Chinese, affecting the bottom biocenoses, also necessitates monitoring in this region.

In the course of the 52nd Russian Antarctic Expedition of 2006-2007 we used the old diving equipment: Sadko-2 suit and ABM-1M aqualung, which we used for 30 years in the Arctic Regions and Far East. Thanks to the producers of this equipment--it worked very well: not a single accident. When preparing the expedition of 2008-2009 we got financial support from the Institute of Arctic and Antarctic Regions and bought new equipment, due to which we could plunge into depths more or less safely.

The work was carried out under the 1.5-2.5 m thick ice, with a few exceptions. Making a crack in the ice for diving took 2-4 hours. Washing of collected specimens, sorting out of the material to determine composition of the species, species predominating in the communities, evaluation of their quantity and biomass also took a lot of time.

PECULIARITIES OF DISTRIBUTION OF FLORA AND FAUNA

The animals and plants on the land near the Progress station are scanty: several bird and mammal species, rare lichens... Under water at a depth of just 3 m the variety of animals is really tremendous.

The bottom in shallow waters and up to 30 m is covered with red algae, Sterechinus neumayeri urchins, sea cucumbers, sponges, sea anemones and ascidians, while bivalved mollusks, polychaetous worms, and other invertebrates hide themselves in the bottom soil. This biocenosis in different modifications is intrinsic to a gently sloping bottom covered with slit and is common in the southern and south-eastern part of Nell's fjord. Various starfishes can be seen there, most numerous for the Antarctic shelf and in fact omnivorous species is Odontaster validus.

The greater part of the bottom is covered with a carpet from Phyllophora Antarctica red algae. The red algae species, belonging to Rhodophyta, plays the most important role in the life of coastal benthic communities of the continent. Together with phytoplankton and diatoms, living on the lower surface of the ice, Ph. antarctica serve as an important component in the food chain, in which the solar energy is transformed into chemical bond energy. In other words, they form organic substances and serve as a source of food for herbivorous animals--urchins, Gastropoda mollusks, and others. In the shallow waters of the Antarctic shelf Ph. antarctica is a leading or predominating (by biomass) species of the community of the same name, including a more or less equal partner--Sterechinus neumayeri urchins. It seems

that these urchins are the main eaters of red algae. Of course, they do not suspect that together with the algae they consume a considerable amount of arsenic--presumably, like all other animals directly or indirectly eating algae. It has been found recently that the phyl-lophora thallomas (bodies) contain (in the form of arsenobetaine salt) up to 0.8 µg of arsenic per 1 g of dry weight of the plant. The fact, which makes clear the existence of increased content of this element in Antarctic sea organisms.

Pink coating is seen on all stones found everywhere. This coating is also a kind of red algae, this time limestone Leptophytum coulmanicum. Despite the thin layer of this coating, the algae cover up to 80 percent of the surface of stones and their total biomass is rather significant.

Large--palm sized--empty Laternula elliptica shells, belonging to Bivalvia mollusks, are found here and there. Later we will find their living representatives. They hide in the soil and are found only due to double siphons--their numerous holes, at the level of the soil surface, cover the bottom at the depths of three to thirty and more meters. They let water through the siphon in order to get some food floating in it. It is very difficult to get out a laternula from the soil.

We tried to dig them out with a knife, but the work was useless: a cloud of dirt immediately goes up, and shell valves are as a rule damaged. A much more effective and simple way is to grip the siphon and pull it up rapidly, as if pulling a mollusk like a carrot from a flower bed. Like many of their relatives in the Antarctic Regions, the laternulas have lecitotrophic (with a reserve of nutrient yolk) larvae, located for some time in the parental mantle cavity. The mollusk thus realizes its care for the progeny, which becomes evident in early southern winter.

There are many light and large band-shaped worms Parborlasia corrugatus at the bottom. Their color varies from white to almost violet in other regions. These worms live in the coastal zones in Argentina, Peru, Chile, South Orkney and South Shetland Islands, around the Antarctic Continent at the depths of 0 to 3,500 m.

Sometimes these worms form large balls, like snakes. P. corrugatus can find food at a distance due to special

chemosensitive cells. The stretching mouth helps them capture a victim as big as a hunter himself. These worms eat everything: sponges, jellyfish, starfish, polychaetous worms, mollusks (even a crest mollusk, despite its large size and ability to jump), Amphipoda crabs, sea anemones, and fish caviar. Even fragments of seal flesh have been found in their digestive system.

It is interesting that these rather large creatures have no respiratory system: they consume oxygen, dissolved in water, through pores by the entire body surface. It is quite enough for them as their metabolism is rather slow and there is plenty of oxygen in the cold Antarctic waters.

Deeper, where red algae form a real carpet, one can see numerous sea cucumbers* of several species. Some are brown, others are pink; they hunt seston** invisible to the explorer. The stars are chaotically scattered--at a distance of 3-5 m from each other.

There are many crowns formed by the sabellide*** (Perkinsiana sp.) tentacles, particularly on rare large stones. These worms are also busy to get food--they capture with their crowns everything that drops from above. Large piles of long white tubes are sometimes seen on large stones, "houses" of Serpulidae common for shallow Antarctic waters; these polychaetous Serpula narco-nensis look like a pack of macaroni. One more species of the same class of worms, though looking quite differently--no tubes or anything of the kind, rather a lanky urchin with a half-transparent body and rare spines--Flabelligera mundata.

Looking more attentively, one can see other red algae, from Polynoidae family. They are flat, their upper part is covered with elytrons (small scales). As was found later, the most common species were Harmothoe spinosa and Barrukia cristata. They are much smaller than their relatives from the same family, living in deep Antarctic waters, such as Eulagisca gigantea--up to 210 mm long and 60 mm wide. Another related species from 30-meter-deep water of Davis Sea--Eulagisca puschkini--is a little smaller: 175 mm long and 55 mm wide. By the way, the Polychaeta class is remarkable not only for shape or size. It has been found recently that they can excrete biologically active substances inhibiting or even blocking cancer cell growth.

The soil, relief, and hence, the fauna are different in deeper waters. At the greatest explored depth (43 m) there predominate Distaplia cylindrica ascidians. These

* Sea cucumbers or holothurians are echinoderms, like urchins and starfish.--Auth.

** Seston-small plankton organisms and organic and inorganic particles suspended in water--Ed.

*** Sabellides are a family of Polychaeta (polychaetous worms), Sabellidae.--Auth.

colonial organisms resemble stearin candles up to 4-5 m long, fixed with their base to small stones or pebble, which serve as anchors. The gas accumulating inside the gel-like colon allows it to maintain a vertical position in water. As the colony grows, the gas accumulated in it, overcomes the "anchor" resistance and the colony, as a giant worm, rises to the water surface or freezes into the formed ice. The formation of bottom ice--a frequent phenomenon in the Antarctic Regions--also helps ascidians to rise to the surface. The "worms" can mislead seafarers and oceanologists, not experienced in zoology. In addition to D. cylindrica, there are many other ascidians, looking like a table lamp or a bunch of some amazing berries or mushrooms. Large brittle stars*, Gorgonaria**, and sponges finish the picture.

Other communities live near the western bank of the bay. Large Isotealia antarctica and Sterechinus neumayeri live in shallow waters on the stones under the ice up to 250 cm thick. In deeper waters they are replaced by Sphaerotylus antarcticus, Calys arcuarius sponges and a belt of limestone tubes of Serpula narconensis Poly-chaeta class. There are also large starfish specimens of up to 30-40 cm in diameter and Parborlasia corrugatus nemertines.

At the depth of 15-18 m and more, the bottom slope sharply changes reaching app. 45° and in some places is even more abrupt. Here we had to descend to a depth of up to 34 m. The narrow stony terraces shaped as uneven steps covered with slit looked like paths of some wild animals and were completely occupied by the "umbrellas" of Perkinsiana sp. Polychaeta and their relatives. There also live a great variety of sponges: half-meter "amphoras" without spines (Anosycalyx (Scolymastra)

* Brittle stars (Ophiuroidea class) are Echinodermata, very much like stars, but with long thin rays.--Auth.

** Gorgonaria order are Octoradlata or sea fans.--Auth.

joubini, up to 2 m high and 1.4 m in diameter), and with spines Rosella nuda; balls--Tetilla leptoderma, Dendrilla antarctica lemon-yellow cactus or Isodictya erinacea golden bunches, fantastical like some exotic plants.

It is extremely difficult to identify the age of sponges. American scientists studying them in Ross Sea shelf noted that various species, including those listed above, remained unchanged throughout several years and then slowly began growing by 10-15 cm during the subsequent 3 or 4 years. It is important that not all of them grow simultaneously, but approximately one half. The above-mentioned A. (Scolymastra) joubini grows on average by 2-3 cm in 10 years. Considering this growth rate, we can suppose that the life span of a sponge of the maximum size we have seen is about 500 years!

Here we saw for the first time a sitting dog's tail grass Lyrocteis flavopallidus. Previously we had met representatives of this animal group only in the thickness of water, while here they sat on the Polychaeta tubes. Lemon-color V-shaped animals, resembling inflated surgical gloves, raised to the surface, transformed into mucus. Peter Brueggemann, German scientist, wrote in his field guide for Ross Sea that L. flavopallidus lived at depths from 32 to 761 m in the Antarctic Regions and near the South Shetland Islands, preferring shallow waters. Reaching 11 cm in height, dog's tail grass throws out a pair of sticky thread-like ramified (from one side) 70 cm long tentacles for capturing food which it directs to the mouth in the lower part of its body, edged with a peculiar sort of a skirt. Due to it, the animal can move along the substrate (sponge, Polychaeta tube, etc.)--very slowly, even slower than a snail-35 cm a day and even slower.

It is rather difficult to support oneself on a steep slope, particularly when your hands are occupied with a pho-tobox, a signal rope, or a bottom scooper for soil collection. It is rather unpleasant when, preoccupied with

work, you start falling with your back to the abyss. So, you should do your best to press the button in time to supply air to the jacket, in order to stop the falling. The water is fantastically transparent in the Antarctic Regions, the objects are seen at a distance of 10-15 m and even more. One feels creepy when "hanging in the air" (not yet working in order to look around or for decompression) holding the rope end and looking down at the walls of a steep slope disappearing in the abyss. The water and the mask glass distort the objects--it seems as if you are inside a giant goblet.

The bottom "population" on the Zong Shan Chinese station beam at the outflow from the bay is similar to the western coast communities. However, there are very few sponges, and the biocenosis of candle-like 5-meter cinascidians starts from 36-37 m. We made this section at a risk of falling under mellow ice. This went on for several days, till a hollow formed near the coast, which could be crossed by swimming or by boat. The ice was so mellow that could be broken almost through by an ice chisel. We had to find a safer place-the other side of the bay. There we dived directly from the coast.

The composition and distribution of animals are different in the small inlets at the other side of the bay.

They have no place to hide on the stone plates, and large sea cucumbers lie on the surface among urchins and rare starfishes. We worked in shallow waters (no deeper than 15 m) there, in sunny weather, when sun rays penetrate through holes in the broken ice. Due to this, the flash did not work, and the photos had a greenish shade.

The "inhibited" behavior of fishes was amazing: bullheads often lay motionless in fissures at the bottom and could be captured by hands--as if they were asleep.

Not far from this region we observed small flocks of swallows. They spoke with each other letting out specific scraping and cracking sounds. Perhaps, they wanted to say something very important...

BASES FOR MANY-YEAR MONITORING

Nine hydrobiological sections were implemented in the course of studies of 24.12.2006-17.01.2007 and 28.12.2008-21.02.2009. Six of them were carried out at Nell's fjord: from southern, western, and eastern sides, at the exit to the straight, and on the Chinese station beam near the eastern coast of the fiord. Three sections were made from the external side, in the Eastern Bay:

near the Chinese station moorage, in Plyazhnaya and Obyezdnaya inlets near the Progress station. Researchers carried out more than 100 diving sessions and spent approximately 40 hours under water. Studies at 27 stations were realized during diving sessions. More than 100 quantitative and qualitative samples of macroben-thos, 30--of meiobenthos, and 20--plankton samples were collected. As a result, reliable bases for many-year biological monitoring were created.

Preliminary results have confirmed rather high biological diversity of the studied water areas near the Progress station, populated by around 600 species of the sea mac-robenthos. The most numerous species have been found for Echinodermata, sponges, Polychaeta class, and ascidians. Several species collected in the bay are presumably new for science. The present studies have shown that red algae (Phyllophora antarctica) and urchins in the shallow waters of the Antarctic Regions (at a depth of up to 20 m) do not predominate everywhere, but as a rule on soft soils. Hard soils are populated by other predominating species--mainly sponges, ascidians, and Polychaeta, phyllophora here are often replaced by limestone algae covering around 80 percent of the area in some places. The benthos biomass in the studied areas at a depth of 3 to 30 m varies from 1,600 to 5,300 g/m², which is characteristic of highly productive areas of the World Ocean.

The work was financially supported by the RF Ministry of Education and Science.