Effect of Artificial Illumination on the Intensity of Nocturnal Vertical Migrations of Amphipods in Lake Baikal

Key words: amphipods, Baikal, daily vertical migrations, artificial illumination, video observations.

Daily vertical migrations (DVMs) of pelagic and even many benthic organisms are characteristic of both marine and continental aquatic ecosystems. The causes of such migrations and factors relevant to them are of great interest of the involved factors is highly interest-ing. For several years, we investigated DVMs of Baikal amphipods (Crustacea, Amphipoda), namely, the noc-turnal migration of many shallow-water benthic species to the pelagic zone. We identified the main life forms of amphipods involved in DVMs, dominant species of the nocturnal migratory complex in several areas of Baikal, and rejected the defense–feeding hypothesis of DVMs traditionally used to explain the vertical migrations of plankton (Takhteev et al., 2000; Mekhanikova and Takhteev, 2001).The prevalence of immature juveniles in the nocturnal migratory aggregations also led to a conclusion that DVMs in most species are not related to reproduction and mating (Govorukhina, 2001). We pro-posed that daily migrations provide for the accumula-tion of a certain sum of temperatures (if a vertical tem-perature gradient is present) or for activation of metab-olism via motion proper in order to complete maturation in due time under conditions of a cold-water lake (Mekhanikova and Takhteev, 2001).

The intensity of DVMs depends on meteorological conditions (first of all, wave height) and illumination on a certain night. The level of illumination is determina-tive in the vertical migrations of Baikal zooplankton (Mogilev, 1955). Previously (Bessolitsyna, 2000), it was noted that the intensity of DVMs of benthic amphi-pods decreased on moonlit nights. In an experiment (Bessolitsyna and Stom, 2001), amphipods making night migrations actively avoided both bright daylight (300–400 lx) and weak artificial light (35–40 lx). On the other hand, we repeatedly observed that a weak arti-ficial illumination (e.g., with a flashlight) attracted amphipods swimming in open water. This fact was used to increase sample size in qualitative collections. At the Baikal Biological Station of the Irkutsk State Univer-sity in Bol’shie Koty, a searchlight installed on the pier had been used for several years to collect amphipods and juvenile sculpin at night. However, it remained unclear if the searchlight attracted nocturnal migrants or just aided in collecting them.

The purpose of this study was to elucidate the effect of weak illumination (in this case, artificial) on the intensity of DVMs. Technical devices for underwater video observations provide new opportunities for inves-tigating the Baikal ecosystem. We have gained the first experience in applying video equipment to studies on DVMs of benthic organisms in Lake Baikal.

Observations were made in the course of expedition aboard the research vessel Professor Treskov (June 2002) at two sites of northern Baikal: in the Solontsovaya Bay on the side of Cape Sagan-Maryan, at the western coast (the area of the Baikal–Lena State Nature Reserve), and in the Peshcherka Bay, on the eastern side of the Bol’shoi Ushkanii Island (figure). The work was done from the vessel anchored in a shoal above a platform.

A Sony TR8000E video camera with an accessory wide-angle lens (to expand the field of view in the aquatic environment) was placed in a sealed box with two 35-V halogen lamps. The signal from the box was transmitted through a cable on deck, where it was recorded by a Hitachi VM-8480LE video camera, with the image being controlled on its color display. Record-ing was made in two modes: under artificial light from the lamps installed on the box and in a night-vision mode, using a built-in infrared emitter of the camera. In both cases, the range of vision was 3–4 m.

Recorded images were analyzed on a wide-screen TV set. Amphipods appearing on the screen were counted using a freeze-frame option when necessary. As some crustaceans could repeatedly enter the field of view, one instance of an animal entering and leaving the frame was recorded as one specimen. Such counting did not allow us to determine the absolute density of crustaceans (per unit water volume) but was appropriate for a compara-tive analysis of their migration activity. Solontsovaya Bay(depth 8 m; June 24, 2002; 1:40−2:25 a.m.). The ground consisted of uneven-sized boulders and pebbles of proalluvial origin, mostly rounded and partly submerged in sand, with single small green sponges.

When the box with lamps onsubmerged, no moving organisms occurred in the field of view, including the period when the bottom was already seen. Before the box reached the bottom, five to eight migrants appeared. Within 10–20 s after the box touched the ground, animal movements became more active: the number of amphipods increased from 2–4 to 10−15 specimens swimming at different distances from the lens. After 1.5–2 min, the number of amphipods in the field decreased again (1–5 ind. per frame). In night-vision mode,no amphipods occurred in the field of vision for 75 s after the box touched the ground for the first time. The box was then transferred to another place, where only a single small amphipod swimming 20 cm above the ground was detected within 25 s. After moving the box along large boulders and placing it on the bottom, amphipods (no more than two specimens per frame) appeared only after 25 s, with the field of view remaining empty most of the time. In a new place, only 11 small amphipods of different spe-cies (precise identification by the recorded image was impossible) appeared before the camera during 160 s. After the next transfer and descent, observations con-tinued for 6 min 55 s, and amphipods (including one egg-bearing female) entered the field of view only six times. No migrants were detected in the course of hoist-ing the box on the deck. Bol’shoi Ushkanii Island(Peshcherka Bay, depth 8 m; June 25, 2002; 2:30–3:10 a.m.). The ground con-sisted of boulders encrusted with sponges on sand with Draparnaldioidesalgae.

When the box submerged with the lamps on, aggre-gations of white swimming amphipods were observed throughout the water column, from the surface to the bottom. They could have been attracted by lights on the deck and on the box, but it appeared that some speci-mens had already been there before the onset of obser-vations. According to our unpublished data, this could have been Micruropus wohliiamphipods, which form mass nocturnal aggregations attracted by the search-lights of vessels in the area of the Ushkanii Islands. The density of migrating amphipods reached a peak at a dis-tance of 2−5 m from the bottom and decreased at greater depths.

Immediately after the box touched the ground and was adjusted horizontally, 50–60 amphipods could be detected in the field of view. They belonged to at least two species: a white one (most probably, Micrurops wohlii) and a dark one. The number of migrants increased by a factor of 1.5 after 30 s and almost doubled after 60 s, with the animals moving closer to the sources of light. A pair of amphipods was noted near the lamps. The density of migrants remained high for 3 min. The white specimens were initially 1.5 times more numerous; later, the proportion of the dark specimens increased, and the ratio of the two forms became equal. The dark amphipods kept closer to the bottom than the white ones: when the lens was directed upward, the latter began to prevail, with the number of migrants in the field of view reaching 180 specimens. When the lens was pointed to an area that had not been illuminated, the recorded density of aggregation proved to be 13 times lower. This fact indicated that artifi-cial light attracted the amphipods. In the course of lifting the box, the highest density of “light” migrants (about 60 specimens in the field of view) was observed at depths of 0.5–3 and 5–7 m. In the night-vision mode,virtually no migrants were detected. In the bottom layer (when boulders appeared), no more than 50 specimens were found in the field of view. When the box touched the ground, they disappeared for a minute because of roiling and then started appearing again, in one or two specimens. The same was observed in a different location. When the box was lifted to the pelagic zone, only three spec-imens appeared on the screen during 20 s. After return-ing the box to the bottom for 4 min 15 s, the migrants were detected in the field of view only twice. Thus, observations at both sites showed that light from the lamps of the video box obviously stimulated the movement of amphipods in the open water of the lit-toral zone. Weak artificial light attracted these animals and activated their migratory behavior. Therefore, the observed decrease in the intensity of DVMs on moonlit nights (Takhteev and Bessolitsyna, 1999; Bessolitsyna, 2000) is probably explained by some as yet unknown factors, rather than by avoidance of moonlight. Video recording does not allow accurate species identification in most cases. It may well be that different species of amphipods respond to artificial light in different ways and the picture observed in this study is averaged. Fur-ther investigations are necessary for elucidating the responses to artificial illumination in different species and life forms of amphipods.

Video observations confirm our earlier conclusion (Govorukhina, 2001) that DVMs of amphipods are not related to mating: in this study, only one pair swimming in the pelagic zone was noted.

Changes in Plankton Abundance, Biomass, and Chemical Composition under the Influence of the Cooling System of the Beloyarsk Nuclear Power Plant

Key words: phytoplankton, zooplankton, abundance, biomass, radionuclides, the Beloyarsk reservoir.

The Beloyarsk reservoir, which supplies cooling water to the Beloyarsk Nuclear Power Plant (NPP) in Sverdlovsk oblast, is an object of multifaceted investi- gation (Guseva and Chebotina, 1988, 1989; Kulikov, 1982; Trapeznikov et al., 1992; Chebotina et al., 1992). To date, however, the influence of the cooling system of the Beloyarsk NPP on phytoplanktonic and zooplank- tonic organisms has not been studied in detail. The available data concern mainly the Konakovo, Kos- troma, and other thermal power stations and are rather contradictory. Some studies indicate the absence of any influence of the cooling system on planktonic organ- isms, whereas other studies demonstrate a stimulating or inhibitory effect. The latter may be related to the fact that investigations are usually performed in the zone of heated water discharge, where conditions are favorable for the restoration of abundance of organisms passing through the cooling systems (Devyatkin, 1975; Elag- ina, 1975; Mamaeva, 1975; Mordukhai-Boltovskoi, 1975; Riv'er, 1975). For this reason, we took samples of plankton immediately at the outlet of the cooling system. Water from the water intake canal supplying it to the cooling system of the NPP was used as a control. The purpose of this study was to analyze changes in the species composition, abundance, biomass, and chem- ical composition of the plankton in the course of its pas- sage through the cooling system of the Beloyarsk NPP.

MATERIALS AND METHODS

In the years 1986-1991, in July, plankton samples were taken immediately at the inlet (the water intake canal) and the outlet of the cooling system (the water dis- charge canal). The phytoplankton was sampled 11 times, and the zooplankton, six times.

To determine species composition, abundance, and biomass of the phytoplankton, samples were taken from both canals simultaneously in two replications, using a water bottle. The samples were preserved, concentrated, and analyzed using a standard hemocytometer chamber under an MBI-15 microscope. Zooplankton was col- lected using a special dip net made of bolting cloth no. 70 and equipped with a bucket. After preservation, the samples were examined in a Bogorov chamber under a binocular microscope. Methods for identifying plank- tonic organisms and determining their abundance and biomass are described in detail in handbooks (Vasil'eva, 1987; Gollerbakh et al., 1953; Zabelina et al., 1951; Kiselev, 1954; Kratkii opredelitel', 1977; Komarenko and Vasil'eva, 1978; Metodika izucheniya, 1975; Metod- icheskie rekomendatsii, 1984). To determine the content of radionuclides and stable chemical elements in the plankton, the latter was collected by special dip nets made of bolting cloth no. 70. As it was impossible to sep- arate phyto- and zooplankton at this stage of investiga- tion, the total plankton was analyzed. The samples were dried in a drying oven at 105~ incinerated in a muffle furnace at 450~ and weighed. The content of 9~ was determined radiochemically; those of 6~ and 137Cs, by gamma-spectrometric methods using an AI-256 multi- channel amplitude analyzer with a Lemon NaJ(T1) scin- tillation detector with a statistical error of no more than 15-29%. The chemical composition of the plankton was determined using a Labtest apparatus.

RESULTS AND DISCUSSION

Table 1 presents the data generally characterizing the species composition, abundance, and biomass of the phytoplankton in the investigated canals. During the period of observations, 61 species of phytoplank- tonic organisms were recorded, with chlorococcous algae (belonging to the Chlorophyta) remaining preva- lent and accounting, on an average, for 38% of the total number of phytoplanktonic species. Blue-green algae prevailed in terms of abundance (80-100%). The most common species of this group included Aphanizome- non flos-aquae, Microcystis aeruginosa, M. pulverea, and Merismopedia tenuissima, Among green algae, Oocystis submarina was relatively abundant.

In terms of biomass, the Cyanophyta, Pyrrophyta, diatoms, and chlorococcous algae proved to be domi- nant in different periods of observation. According to the averaged data, however, the biomass of Cyanophyta clearly prevailed over that of other algae, accounting for approximately 70% of the total average for the phy- toplankton.

Table 1 shows that the abundance and biomass of different algae was markedly higher in the water intake canal than in the discharge canal. As averaged over the period of observations, the abundance of phytoplank- ton decreased upon the passage through the cooling systems by a factor of approximately 2, and its biomass decreased by a factor of 1.6. Table 2 demonstrates the average annual data on the total phytoplankton abun- dance and biomass, and the same parameters exist for the prevailing types of algae. In most cases, the param- eters recorded in the water discharge canal were signif- icantly lower than those in the water intake. It should be noted that the levels of abundance and biomass in the water intake and discharge canals were relatively high, compared with the corresponding aver- * Calculations performed without taking into account samples taken on July 31, 1990 at a peak of Cyanophyta abundance. age levels for the water body (Guseva et al., 1989). This is apparently explained by the fact that the cooling sys- tem receives water mainly from the surface layers, which are richer in phytoplankton than bottom layers. Hence, our data on phytoplankton abundance and bio- mass should not be extrapolated to the entire water body, as they only pertain to the aforementioned canals. The zooplankton was represented by 17 species belonging to two classes: Crustacea (nine species of the order Cladocera and four species of the Copepoda) and Rotatoria (four species). In terms of abundance and biomass, crustaceans obviously prevailed over rotifers, accounting for about 90-99% of the total zooplankton. As in the case of phytoplankton, the abundance and biomass of zooplanktonic organisms noticeably decreased after passing through the cooling installa- tions of the NPP. This was clearly observed with respect to the total average abundance and biomass of zooplankton (which decreased by factors of 3 and 2, respectively) and the corresponding parameters for individual classes and orders of zooplanktonic organ- isms. Table 4 shows that this difference between the water intake and discharge canals was revealed in dif- ferent years, with the values of zooplankton abundance and biomass decreasing by a factor of 2 to 5.

These results demonstrated that water passage through the cooling systems of the Beloyarsk NPP has an obvious damaging effect on phytoplanktonic and zooplanktonic organisms, which may be attributed to rapid water heating (by 8-9~ and traumatization of small aquatic organisms passing with cooling water through pumps and condenser tubes (Kulikov, 1978). It was interesting to estimate the proportions of undamaged and destroyed organisms in the phy- toplankton and zooplankton passing through the cool- ing system. These calculations were based on the aver- aged values of phytoplankton and zooplankton biomass in the investigated canals (Tables 1, 2) and the average monthly water volume passing through the water intake canal into the cooling system (65 x 106 m3). Table 5 shows that approximately 173 metric tons of phy- toplanktonic organisms and 11 t of zooplanktonic organ- isms per day are pumped in with water from the intake canal. Approximately 62% of phytoplanktonic and 45% of zooplanktonic organisms return to the reservoir through the water discharge canal without any apparent damage, whereas 38% of phytoplankton (65 t/day) and 55% of zooplankton (6 t/day) perish and tum into detri- tus, which is released in the cooling reservoir with heated water and, probably, is partly retained in the cooling systems.

The content of radionuclides in the plankton of the investigated canals varied in different years of observa- tions (Table 6). The increased values were obtained in 1986, when the second and third units of the NPP were functioning. In 1990 and 1991, after the second unit was put out of operation, the concentration of radionu- clides in the plankton noticeably decreased. Subse- ~0~ent observations revealed no differences between o and 137Cs concentrations in plankton samples from the water intake and water discharge canals. Regarding the plankton as a bioindicator of radioactive water con- tamination, it may be concluded that the operating third unit of the Beloyarsk NPP released no additional 6~ and 137Cs radionuclides into the reservoir through the cooling system. On the whole, radionuclide concentra- tions in the plankton of water intake and discharge canals are comparable with those in plants and grounds of the Beloyarsk reservoir (Chebotina et al., 1992). In 1985, the chemical composition of plankton before and after its passage through the cooling system was investigated (Table 7). In the water discharge canal, the plankton contained much more macro- and micro- elements than in the water intake canal. It may well be that chemical elements were adsorbed on particles and retained by dip nets in the course of plankton sampling. On the other hand, they could be absorbed by plank- tonic organisms in the course of their passage through the cooling system. In the present study, we did not determine whether these elements were stable or radio- active. In any case, when the second unit was operating (1985), they were released into the cooling reservoir and contributed to water contamination. Similar data were obtained for the cooling reservoir of the Kursk NPP (Vereshchak et al., 1996).

On the Problem of Flora Formation in Industrially Disturbed Land Areas

Key words: flora, industrially disturbed lands, taiga zone.

A major part of the global population already lives amid so called technogenic landscapes, in which industrial waste dumps and other types of disturbed land areas have a special place with regard to deleteri ous effects on the natural environment and human health. In Sverdlovsk oblast, they concentrate in the vicinities of all large cities and most other populated areas, covering more than 63 300 ha of land (Chaikina and Ob’edkova, 2003). Such territories are initially devoid of the soil and plant cover, and their ecologi cally specific substrate lacks the pool of seeds and other viable diaspores. Hence, the establishment of plants in them starts from point zero.

Studies on specific features of flora formation in such areas are of theoretical and practical significance for their biological recultivation and restoration of biological diversity. Problems concerning specific fea tures and patterns of these processes in industrial waste dumps have been considered in recent decades in many countries (Burda, 1991; Rostanski and Wozniak, 2000; Tokhtar’ et al., 2003; Tokhtar’ and Kharkhota, 2004). Intensive studies on bioecological characteristics of corresponding floras are performed in Ukraine (Bashuts’ka, 2002; Zhukov et al.; 2004, Yaroshchuk et al., 2007).

The purpose of this study was to reveal consistent trends in the restoration of floristic diversity in indus trially disturbed lands using the example of such areas in the taiga zone.

The objects studies in Sverdlovsk oblast were as fol lows: spoil banks of open cut bauxite mines near the city of Severouralsk (below, designated L 1); the southern spoil bank of the Veselovskoe lignite mine near the city of Karpinsk (L 2); refuse dumps of the foundry sand pit in the village of Basyanovskii (L 3); ash dumps of district power plant (DPP) in the city of Verkhnii Tagil (L 4); spoil banks of the Estyuninskii open cut iron ore mine near the city of Nizhnii Tagil (L 5); spoil banks of coal mines near the village of Bulanash (L 6); spoil and tailing dumps of dressing plants at the Bazhenovskoe serpentine asbestos mine, the city of Asbest (L 7); spoil and tailing dumps of the Pervouralsk titanomagnetite ore mine, the city of Per vouralsk (L 8); and spoil banks of Bilimbaevskoe flux ing limestone mine, the village of Bilimbai (L 9).

In Chelyabinsk oblast, studies were performed on spoil banks of Cheremshanskoe nickel ore mine near the city of Verkhnii Ufalei (L 10). The rock composi tion of the above dumps was briefly described previ ously (Chibrik, 2007).

The flora of these sites was characterized on the basis of geobotanical releves compiled for plots with different aged phytocenoses by conventional methods (Korchagin, 1964) and the results of additional route surveys. The age of sites was estimated from mine sur veying data. On the whole, 15–30 releves were made for each site. The initial floristic lists were published previously (Chibrik and El’kin, 1991).

Substrates of the sites are poor in nutrients, stony, and contain no soil (therefore, no plant diaspores). Therefore, the formation of their vegetation in the course of spontaneous overgrowing follows the pattern of primary succession as determined by Shennikov (1964). The age of the sites is young to medium, with the vegetation including serial phytocenoses up to 25– 30 years of age.

The species richness of individual local floras ranges from 57 to 149 in dependence on ecotope diver sity, which is minimum on the Estyuninskii spoil bank (L 5) and maximum on the ash dump of Verkhnii Tagil DPP (L 4), where herbaceous communities develop along with forest communities. The lowest fluctua tions of species composition (from 75 to 88 species) are characteristic of five sites with typical forest com munities.

Data on the bioecological structure of floras in industrially disturbed sites of the forest zone are shown in the table. Mesophytes dominate in all plant com munities, with their proportion ranging from 59.7% on spoil banks of coal mines in Bulanash (L 6) to 84% on those of the Pervouralsk titanomagnetite ore mine (L 8). The total proportion of mesophytes and xer omesophytes varies from 76 to 91% of the total species number. An analysis of life forms according to Raun kiaer’s scheme provides evidence for the prevalence of hemicryptophytes and considerable role of geophytes, with phanerophytes being dominant. Spoil banks of Bulanash coal mines (L 6) are an exception, since only herbaceous communities develop on them. With respect to the mode of fruit and seed dispersal, structural rearrangements in the floras involve three groups: autochores + barochores, zoochores, and hemianemochores + anemochores. In the floristic composition of communities following the forest pat tern of development, the proportion of zoochores reaches 27.9% (spoil banks of Severouralsk bauxite mines, L 1). In sites where only herbaceous commu nities develop (spoil banks of Bulanash coal mines, L 6) or such communities prevail (ash dumps of Verkhnii Tagil DPP, L 4), this proportion decreases to 14.5 and 17.5%, respectively. All floras contain a considerable proportion of anemochorous and hemianemochorous species, which decreases as the tree layer develops and crown closure increases. It should be noted in this context that dominants and the majority of species in the tree layer are anemochores. Forest communities with tree crown closure of about 0.4–0.8 grown on spoil banks of Basyanovskii sand pit (L 3), Estyunin skii iron ore mine (L 5), and asbestos mine (L 7) and contain 29.4–32.0% of species with the anemo chorous type of seed dispersal. The proportion of such species increases in communities where the degree of crown closure is lower (no more than 0.5) and reaches a peak of 49.4% in the flora of coal mine spoil banks, where only herbaceous plants can grow because of unfavorable ecological conditions (cone shaped mounds, stony substrate with acid pH, poor nutrient supply, etc.).

In terms of landscape–zonal classification, three prevailing groups can be distinguished: ruderal, forest, and meadow species (see table). The proportion of ruderal species depends on the degree of plant com munity development, decreasing in medium aged communities. Other relevant factors are the pattern of vegetation in surrounding areas and properties of the sub strate. Thus, Severouralsk (L 1), Yuzhnoe Veselovskoe (L 2), Basyanovskii (L 3), and Estyuninskii (L 5) spoil banks are surrounded by forest, and the propor tion of ruderal species is small even in communities formed in their “youngest” areas. A relatively high percentage of meadow species is due to incomplete canopy closure and large glades at forest margins, as well as to a major contribution to plant communities at early stages of their formation.

Analyzing local floras, we calculated the grades of species constancy as the sum of constancy classes in plant communities of all sites studied in the taiga zone. The constancy class of a species in each site was deter mined from the percentage of cenoses in which the species was recorded relative to the total number of cenoses described in the site (Shennikov, 1964): class I, 1–10%; class II, 1–20%; class III, 21–30%; …; class X, 91–100%. Thus, a species described in more than 91% geobotanical releves (i.e., sampling plots) was assigned the highest constancy class X. The high est possible grade of species constancy in the taiga zone was 100, indicating that the species had con stancy class X in all ten sites studied within this zone. The grades of species dominance were calculated in the same way.

The constancy grade characterizes the activity of species expansion to technogenic landscapes (Yurtsev, 1982; Didukh, 1982). Among 260 species described in industrially disturbed sites of the taiga zone, high con stancy grades (>50) were assigned to 13 species: trees Pinus sylvestris L. (66), Betula pendulaRoth (59), and Salix capreaL. (59) and herbaceous plants Chamaen erion angustifolium(L.) Scop (81), Tussilago farfaraL. (79),Achillea millefoliumL. (70), Trifolium pratenseL. (63), Taraxacum officinaleWigg. (62), Poa pratensisL. (59), Amoria repens(L.) C. Presl (56), Cirsium setosum (Willd.) Bess. (52), Festuca rubraL. (52), and De schampsia cespitosa(L.) Beauv (50). Many of them dominate in developing phytocenoses with respect to coverage and abundance. The above species comprise the core of floristic complex in the sites studied. Bioecological parameters of these species show that most of them are perennials (88.1% of the total species list). However, an important phytocenotic role at early stages of plant cover development in lifeless technogenic ecotopes is played by annuals and bienni als, which dominate in abundance and biomass in some sites. Mesophytes account for 71.5% of the spe cies list and are represented by different life forms (according to Raunkiaer): hemicryptophytes prevail (31%), with the total proportion of these species together with herbaceous chamaephytes and the inter mediate group of geophytes–hemicryptophytes reaching 64.3%; phanerophytes account for 16.7% (being dominant by other parameters); and the pro portion of therophytes and therophytes–hemicrypto phytes (annual and biennial) is only 11.9%. In terms of landscape–zonal classification, meadow and forest species prevail (35.7 and 23.9%), but proportions of ruderal and meadow–ruderal species are also consid erable (19.0 and 14.2%, respectively). The results of aerographic (ecogeographic) analysis confirm the prevalence of boreal species (85.7%; together with polyzonal species, 95.2%) among latitude groups and of Eurasian (52.4%) and circumpolar species (23.8%) among longitude groups.

A comparative analysis of these results and published data (Chibrik and Kravchenko, 1990; Bashuts’ka, 2002; Tokhtar’ and Kharkhota, 2004) provides evidence a zonal trend in the establishment of vegetation in techno genic barrens: new phytocenoses develop so as to approach the pattern of natural vegetation surround ing the technogenic ecosystem. This applies not only to the forest zone of the Urals but also to other natural zones, including the forest–steppes of the Urals and Ukraine. An additional argument in favor of this con clusion comes from floristic lists of herbaceous vegeta tion on spoil banks of some Ural iron ore mines, on substrates with a high content of stones and unfavor able ecological conditions (Chaikina and Ob’edkova, 2003): depending on the site, these lists range from 10 to 66 species.

Thus, against the background of general zonal trend in the formation of local flora, conditions char acteristic of a given technogenic site have a major, often decisive effect on this process. Therefore, analy sis of the structure of local floras can be used for esti mating the potential of disturbed land areas for biolog ical recultivation.

Geographic Trends in the Accumulation of Heavy Metals in Mosses and Forest Litters in Karelia

Key words: heavy metals, accumulation, mosses, litters, Karelia, multivariate statistical analysis.

Heavy metals (HMs) are considered to be among priority technogenic pollutants. To solve ecological problems related to the environmental effects of HMs in the Russian North, it is necessary to make a detailed inventory of their contents in natural objects in different areas with regard to the diversity of climatic and soil-geochemical conditions and the degree of industrial development in these areas. It is known that mosses are informative indicators of aerotechnogenic environmen-tal pollution. Forest litters are important as the struc-tures retaining and accumulating various pollutants.

The contents of HMs in the soil depends on the distance from local pollution sources and, to a large extent, on the pattern of pollutant transfer in the upper layers of the atmosphere. An important role belongs to region-specific natural factors, i.e., local climate, relief, vege-tation, and soils. The Republic of Karelia is located on the Baltic shield, which forms the northwestern part of the Russian platform. The vast area of the republic (117300 km 2 ) extends from the north to the south for 672 km; hence, the climate, geological structure, hydrographic net-work, soils, and vegetation in different parts of the republic are heterogeneous. The climate in Karelia is relatively mild, with a long mild winter and a short cool summer; considerable cloudiness, high humidity, and changeable weather are characteristic of all seasons. The prevailing form of atmospheric circulation over the territory of Karelia is the western transfer of air masses. The formation of precipitation is also accounted for by moisture evapo-rated from the White Sea and numerous lakes and bogs, which cover one-third of the Karelian territory. Vegeta-tion has a considerable effect on the migration of sub-stances. In Karelia, coniferous forests are the dominant type of vegetation.

The spectrum of possible sources of technogenic HM pollution in Karelia is wide. There are 10284 sources of industrial emissions into the atmosphere, and most of them are concentrated in the cities of Petrozavodsk, Segezha, Kostomuksha, and Kondo-poga. The total amount of emissions from large indus-trial enterprises of these cities reaches 128600 tons per year. A complex combination of technogenic factors and natural geochemical conditions in Karelia deter-mines the pattern of HM distribution over its territory. In this work, we studied green mosses (Pleurozium schreberi, Hylocomium splendens) and forest litters. The former indicate the state of the atmosphere over a relatively short period of time (approximately three years), and the chemical composition of the latter reflects the impact of long-term industrial pollution (over more than ten years). The chemical analysis of mosses and litters can provide information about the sources, ranges, and extents of environmental pollu-tion, as well as reveal major pollutants. Our studies were performed by internationally accepted methods (Atmospheric Heavy Metal…, 1996).

Samples of green mosses and forest litters were taken from test plots of the bioindication network cov-ering the entire Karelian territory. The contents of iron, manganese, chromium, copper, nickel, zinc, cobalt, lead, and cadmium in the samples were determined by atomic absorption spectrometry.

We also estimated the effects of climatic parameters (wind rose, precipitation rate) on the distribution of aerotechnogenic pollutants containing HMs over the territory of the republic. The data on each of eight wind directions recorded by the Karelian hydrometeorologi-cal observatory (N, S, W, E, NE, NW, SE, SW) was assessed quantitatively with respect to wind stability, i.e., the frequency of its occurrence as a percentage of the total number of observations (without calm winds). Taking into account wind directions in winter and sum-mer and different weather patterns in the cold or warm periods of the year, the parameters of stability were averaged. Thus, we distinguished cold winters with lit-tle snow from warm, snowy winters and cold, rainy summers from warm, dry summers.

We developed an original approach to the analysis of HM distribution over the Karelian territory with respect to each individual element and their combinations, Geographic Trends in the Accumulation of Heavy Metals in Mosses and Forest Litters in Karelia which allowed us to assess the structure of their emis-sion from different sources. This approach involves the combined use of the methods of multivariate statistical analysis in the following sequence: stepwise regression analysis is used for selecting the most efficient climatic indices for each element; factor analysis, for assessing the structure of HM distribution with respect to combi-nations of elements; and stepwise discriminant analy-sis, for estimating the correctness of results obtained at the preceding stages. Another reason for using factor analysis is that HMs are distributed over the territory in certain combinations, rather than individually. Our results confirmed this fact (see below).

Regression analysis was used for assessing HM accumulation in mosses and forest litters with regard to the effects of most significant climatic indices on each element (Table 1). The results showed that precipitation generally has a weak effect on HM distribution; we can note only a slight influence of this parameter on the deposition of copper, nickel, and cadmium. Westerly winds bring to the Karelian territory mainly cobalt, lead, chromium, and manganese; east-erly winds, zinc and lead; northerly winds, zinc and nickel; and southerly winds, chromium and lead. The input of lead depends on winds to the greatest extent. The westerly winds are responsible for the distribution of a broader spectrum of HMs. The regression analysis of HM distribution and accumulation in green mosses and litters produced similar results. By factorizing the matrices of correlation between the values of pollutant distribution in mosses and forest litters, calculated by regression equations, we identified three factors (F1 , F2 , and F3) accounting for 80.0 and 77.1% of the total variance for mosses and litters, respectively. Each factor reflects one aspect of the inter-nal structure of HM combinations formed upon their distribution over the territory of Karelia (Table 2). Mosses.By F1 , the combination of Zn, Cr, Co, and Pb is distinguished (high positive loads). Factor F2, by high positive loads, reflects the distribution of the com-bination of copper and manganese over the territory. High negative loads may be used for tracing pollution with lead and cadmium, with the prevalence of the lat-ter. By F3, the combination of iron and nickel is distin-guished (high positive loads); a small negative load indicates the distribution of cobalt over the territory. Forest litters.By F1, the combination of manga-nese, cobalt, iron, and copper (with the prevalence of manganese) is distinguished (high positive loads). F2 indicates the distribution of iron, cadmium, zinc, and chromium, with the prevalence of iron (high positive loads). By F3, the combination of copper and cadmium (with the prevalence of copper) is distinguished (high positive loads).

According to the pattern of object distribution (the proximity of their coordinates in a three-dimensional space), five groups of administrative districts (raions) (I–V) were distinguished, which correspond to the areas where mosses and forest litters were polluted with HM combinations accounted for by each of the three factors:

(I) Loukhskii, Kaleval’skii, Kemskii, Muezerskii, Belomorskii raions and the city of Kostomuksha; pol-lutants: nickel, copper, manganese, and iron in mosses; cadmium, iron, chromium, zinc, copper, and nickel for litters.

(II) Segezhskii and Medvezh’egorskii raions; pol-lutants: copper, cobalt, chromium, lead, zinc, cadmium, and manganese in mosses; cobalt, nickel, cadmium, zinc, iron, and lead in litters.

(III) Pitkyarantskii, Sortaval’skii, Lakhdenpokhskii, and Suoyarvskii raions; pollutants: nickel, cobalt, chro-mium, lead, cadmium, zinc, and iron in mosses; cad-mium, nickel, and lead in litters.

(IV) Pryazhinskii, Kondopozhskii, Olonetskii, Pri-onezhskii, and Vepskii raions; pollutants: cobalt, lead, and cadmium in mosses; cobalt, manganese, copper,

iron, lead, and nickel in litters. (V) Pudozhskii raion; pollutants: chromium, lead, cobalt, zinc, copper, and manganese in mosses; iron, cadmium, copper, chromium, zinc, cobalt, and manga-nese in litters.

To estimate the correctness of grouping (homogene-ity within each group and heterogeneity of different groups), stepwise discriminant analysis was used. Its results confirmed that all five groups were identified correctly: they proved to be internally homogeneous and did not overlap with one another. The main dis-criminators (major pollutants) in forming regional groups with respect to the pollution of mosses are nickel, cobalt, chromium, and cadmium. According to their significance for group formation, they can be arranged in the following series: Co > Cr > Ni > Cd. In the case of forest litters, the main discriminators arranged in the same order are as follows: Fe > Mn > Pb > Zn.

The results of pairwise comparisons of the regional groups in the three-factor spaces with respect to HM contents in mosses and forest litters (Table 3) demon-strated that differences were significant only for groups I and II, especially concerning the contents of cad-mium. In the second group (Segezhskii and Med-vezh’egorskii raions), differences between HM accu-mulation in mosses and forest litters were significant for the majority of elements (especially for copper) and nonsignificant for zinc and iron.

Thus, we revealed the existence of geographic trends in the distribution of pollutants over the Karelian territory and their accumulation in mosses and forest litters.

On the Problem of Anthropogenic Influence on Mammals of the Prepolar Ural Mountains

The eastern macroslope of the Prepolar Urals is inhabited by 40 mammalian species. Unique species diversity associated with a great variety of mountain landscapes is preserved in this relatively small area because of a low degree of anthropogenic impact. This study is an attempt to estimate the consequences of considerable intensification of human activity planned in connection with the exploitation of placer deposits. Previously, such work caused slight damage to terres- trial ecosystems because it affected the area of only 0.6--1.0 km 2 in each case. Nevertheless, these examples allow one to predict, to a certain extent, the trend of subsequent development of the anthropogenous pro- cesses in natural landscapes of the region. For a number of years, I studied the state of mam- malian populations in the regions of placer deposits, other mining enterprises, and wilderness areas. Large mammals. Route censuses of animals and their tracks were taken. Among large mammals, moose and bears prevail in the region (Flerov, 1933). On aver- age, one moose track and one bear track crossing the route were registered each 1.5 and 2 km, respectively. The tracks following along the route were not found on rock dumps of gold mines but occurred in river valleys not disturbed by mining. The tracks across the route were often near ravines joining the valley. The absence of differences between the results of censuses taken on rock dumps and in undisturbed areas is explained by the fact that the home ranges of these animals are con- centrated in ravines and on the slopes of mountain spurs. Bears in summer also occur in mountain tundras; they cross river valleys during daily migrations from one slope to another. Moose prefer forested slopes; hence, their routes across river valleys were mainly in the middle reaches, i.e., in the zone where gold placers are commonly located. Consequently, further develop- ment of gold mining in this region can have serious ecological consequences. The exploitation of large river valleys and neighboring tributaries of the same river system will result in the fragmentation of animal home ranges. In the summer and winter seasons, each individual range occupies 2.5-39.0 and 0.8-7.5 km 2, respectively (Filonov, 1993). Therefore, the loss of sev- eral parts of these ranges, even as small as i km 2 in area, will result in the substantial reduction of the total area inhabited by individual animals, and, conse- quently, in the decrease of animal abundance. Further development of mining in the Prepolar Urals will interfere with seasonal migrations of moose, preserved population of wild reindeer, and a number of rare (e.g., wolverine) and valuable commercial species (sable and marten). The point is that these migrations are generally directed from the plain to the mountains and back; hence, as mining is carried out on tributaries of large rivers flowing down from the main watershed, areas with depleted deposits in river valleys cut across the migration routes. As shown in some other regions of the Urals (Bukhmenov, 1975; Filonov, 1993), the gen- eral migration flow separates in such cases into discrete streams, traditional migration routes are displaced to new, less convenient locations, and the intensity of migration decreases. As a result, some animals winter under less favorable conditions, and their mortality increases.

An important role belongs to the effects of other industrial activities and anthropogenic factors associ- ated with mining, such as road construction, land clear- ing for house building, cutover and burned-out areas appearing in the forests, uncontrolled hunting, and anx- iety. Apparently, their adverse consequences will become even more serious with the expansion of min- ing industry. The road network will create additional barriers to animal migration; tree cutting and burning in large areas will bring about significant changes in food composition and supply of both herbivorous and pred- atory mammals, which lead to a short-term increase and subsequent decrease in animal abundance (Smirnov, 1987). Anxiety among animals will have the gravest consequences, making them migrate to the areas remote from the zone of industrial development and concentrate there. This primarily concerns herbiv- orous mammals. In the Prepolar Urals, where the productivity of ecosystems is relatively low, this process will soon result in the depletion of food resources and the consequent decrease in animal population size, as it occurred with wild reindeer. To date, the local popula- tions of large mammals have not been seriously affected by uncontrolled hunting. In the Man'ya River basin, for example, the estimated size of moose popu- lation is approximately 200 animals, commercial hunt- ing is virtually absent, and only two or three geologic field crews usually work in this region; as members of each crew shoot one or two moose per year, the total annual loss is only three to six animals, i.e., 1.5-3%. However, hunting pressure on these populations can rapidly exceed the allowable limit and result in their decline.

The aforementioned consequences of industrial development are equally unfavorable for representa- tives of the family Mustelidae. Small mustelids, such as weasels and ermines, have home ranges of several doz- ens of hectares (Danilov et al., 1979) but never inhabit the areas of rock dumps; hence, the appearance of each depleted mining site reduces the populations of these species by one or several individuals. Damage from mining is virtually irreversible, as the disturbed biogeo- cenoses will apparently recover for centuries (the areas of mines abandoned half a century ago are almost in the same state). Small mustelids face the risk of losing con- siderable proportions of their existing populations. This especially concerns ermines, which prefer floodplain biotopes. As to large mustelids, their home ranges cover dozens of square kilometers, and the effects of mining on these animals will be comparable to those on bears and ungulates.

A relatively low population density of large mam- mals is characteristic of the entire Prepolar Urals (Fle- rov, 1933; Laptev, 1958; Berdyugin, 1997), and its gradual decrease under the effects of anthropogenic factors can rapidly bring many species to the point of extinction. Therefore, instead of developing the mining industry in this region, it would be expedient to orga- nize there a specially protected area (e.g., national park) providing for the conservation of the entire com- plex of natural conditions, including the species diver- sity of mammals. This measure will also prevent pollu- tion of the rivers that provide spawning grounds for valuable fish species.

Small mammals. The species of this group (rodents and shrews), owing to their great abundance and diver- sity, play an important role in the processes occurring in natural communities. Differing from each other in biological requirements, they perform different func- tions in the communities and can promote their devel- opment in one direction or another, depending on exist- ing conditions.

The material on small mammals was collected in the main types of their habitats, both natural (27 types) and anthropogenically transformed to a greater or lesser extent (11 types). The results of this investigation are shown in the table.

In the Prepolar Urals, this animal group is repre- sented by ten species, two of which occur only in their natural habitats and are absent from anthropogenically transformed biotopes. A decrease in species diversity indicates degradation of animal communities. On the other hand, water voles appeared in the same areas. The occurrence of this species in the mountains provides evidence that human activities resulted in the expansion of river segments with a slow current and loose soils on the banks. This also follows from the fact that the abun- dance and proportion of root voles--rodents character- ized by a similar mode of life increased in the com- munities of anthropogenically transformed habitats (Berdyugin, 1985). The expansion of such landscape elements in the mountains can have grave conse- quences, as strong spring and rain floods, which are common in this zone, inevitably wash the soil away and denude the banks.

In general, the structure of rodent communities in natural habitats is characterized by the following fea- tures. The total number of rodents is relatively low: this is evidence that the productivity of both rodent commu- nities and biocenoses of the Prepolar Ural Mountains as a whole is also low. The northern red-backed vole is the dominant species accounting for almost half the total number of rodents in the communities. The large- toothed red-backed vole, a specific mountain species in the Urals, is subdominant. Three species--bank, field, and Middendorff voles--are common and fairly numerous components of the communities. Other spe- cies are relatively rare. In anthropogenically trans- formed habitats, the species ratio changes substantially: the proportions of the dominant species and large- toothed red-backed voles decrease, whereas those of bank voles (more typical for the southern taiga) and Middendorff voles (inhabitants of open tundra areas) increase. Changes in the proportion of root voles in rodent communities were considered above.

All distinctive features of rodent communities in the anthropogenically transformed habitats indicate that these areas are losing the landscape pattern characteris- tic of the Prepolar Urals, i.e., coniferous forests are replaced by deciduous ones, treeless areas increase in size, and the structure of the herbaceous layer changes. In addition, the system of slowly flowing streams is formed (see above). Thus, landscape formations char- acteristic of plains and atypical for highlands appear in the mountain area. They are extremely insecure under conditions of the mountain relief and cannot provide for its stabilization. These events in their natural course can lead to a general landscape crisis (Makunina, 1974).

The survey of areas exposed to less destructive anthropogenic influences several decades ago showed that changes in plant and rodent communities are gen- erally interconnected. When the cessation of mining is followed by the development of birch, mixed conifer- ous-birch, and, at later stages, birch--coniferous herba- ceous forest communities, bank voles become domi- nant in the rodent community, and field voles increase in number. Rodents can be abundant in such forest bio- cenoses. Because of certain ecological peculiarities (primarily those of feeding), these species interfere with the reverse transformation of biocenoses into their initial state, i.e., the state of equilibrium under given environmental conditions. When anthropogenic effects result in predominant development of herbaceous asso- ciations, rodent communities are characterized by increasing proportions of field voles and, in mountain tundras, Middendorff's, bank, or gray-sided-backed voles. The ecological effect of this phenomenon is the same as in the previous case. Disturbed sites are often occupied by plant communities with a weakly devel- oped herbaceous-moss layer and low productivity (even by local criteria). They are usually inhabited by northern red-backed voles, but the density of these ani- mals is extremely low. Finally, the variant closely resembling the situation on fresh rock dumps was observed in the areas where the plant cover and soils were largely (but incompletely) destroyed in the course of mining. The recovery of the biota in this case is com- plicated and proceeds extremely slowly. For example, a site of the sedge-moss tundra exposed to such an impact more than 50 years ago is still uninhabited by rodents.

To date, the biotic complex has been completely destroyed in relatively small areas. However, further development of gold mining and the resulting expan- sion of such areas in the Prepolar Urals may have grave consequences, up to the point of ecological disaster.

On the Problem of Steppe Ecosystem Conservation in the Central Caucasus

Key words: the Caucasus, steppe ecosystems, Arik Ridge, nature reserve.

 The steppe biomes of Russia are endangered, and remaining steppe ecosystems have degraded to differ-ent extents under the impact of human activities. The main destructive factor is extensive agriculture, which cannot be profitable without expansion to new areas. The Caucasus as a whole and particularly the Northern Caucasus, one of the most densely populated regions of Russia with an economic system based primarily on agriculture, are not an exception.

Natural steppe ecosystems in the Northern Cauca-sus occupied western and central Ciscaucasia within Krasnodar and Stavropol regions, the Adygei and Kab-ardino-Balkar republics, and North Ossetia, giving way to semidesert ecosystems in plain and foothill areas lying farther east. Although the natural range of steppe cenoses in the region is limited and exposed to signifi-cant anthropogenic impact, there is not a single nature reserve established in order to conserve the steppe eco-systems of the Northern Caucasus. Piedmont forests are the main protected biomes in the Caucasian, Teberda, and North Ossetia nature reserves; subalpine and alpine meadows, in the Kabardino-Balkar High Mountain Reserve. In the Dagestan Reserve, which consists of two separate areas, attention is focused on the conser-vation of desert landscapes and coastal ecosystems of the Caspian Sea region. The necessity of establishing a forest–steppe nature reserve was substantiated by spe-cialists of Stavropol State University in 2000 (Godzevich et al., 2000).

Although the flora and fauna of the Northern Cauca-sus are unique among mountain regions of Russia, the total size of specially protected natural areas (SPNAs) in the region is the smallest, and the pattern of their dis-tribution (in clusters) does not comply with the require-ment for representativeness of the protected biota (Tishkov and Belonovskaya, 2004). Among measures to conserve steppe ecosystems in the Kabardino-Balkar Republic, of primary importance is the establishment of a nature reserve as the most effective type of SPNAs with regard to protection of ecosystems and their com-ponents. Basic criteria for identifying areas of nature-conser-vation significance are the systems of parameters char-acterizing the state of botanical and zoological objects.

In the former case, these are parameters such as rarity of plant communities, their floristic and phytosociolog-ical significance, reduction of their ranges, and the risk of their extinction (Zhuravleva, 1999). In 2006, special-ists of the Institute of the Ecology of Mountain Areas surveyed steppe ecosystems made in Maiskii, Prokhlad-nenskii, and Terskii raions of the Kabardino-Balkar Republic. The results of this survey show that relatively small areas of virgin land on the Arik Ridge fully sat-isfy the above criteria. The fact that these areas still retain their natural steppe vegetation has also been noted by other authors (Kos, 1959; Kerefov and Fiap-shev, 1977; Shkhagapsoev and Volkovich, 2002). Physiographic characteristics.The Arik Ridge, located in the northwest of the republic (43°20′–43°50′N, 44°–45°E), is actually a system of spurs of the Terek Ridge with a subdued topography and elevations of no more than 450 m a.s.l. The watershed and slopes are composed of Pliocene sand–clay conglomerate rock masses. Prevailing soils are micellar, calcareous, ordi-nary chernozems with low or medium humus contents (Kerefov and Fiapshev, 1968). According to physio-graphic zoning of the Northern Caucasus (Chupakhin, 1974), this area is in the Kabarda sloping-plain region of the Mineralnye Vody–Terek district of the Stavropol–Terek province (Central Ciscaucasia). Its climate is moderately continental, with annual average temperature and precipitation of 11.0°C and 522.6 mm (according to meteorological data from the city of Terek between 1987 and 2002) (Ashabokov et al., 2005). The bulk of precipitation falls in summer but is largely lost by evaporation and surface runoff. The area has no natural sources of water and receives it from the irrigation system that includes the Malo-Kabardinskii, Akbashskii, and Tambovskii canals.

Phytocenotic and floristic diversity.According to florogenetic zoning of the Central Caucasus (Galushko, 1976), the Arik Ridge is in the Terek–Sunzha region of the Ciscaucasian district of the Kuban–Terek piedmont steppe province. According to the results of the 2006 survey, its natural vegetation is composed mainly by herb–grass, grass–legume–herb, grass–wormwood, herb–licorice, and, to a lesser extent, beard grass, feather grass, and shrub–herb phytocenoses. Among grasses, common are steppe species such asKoeleria cristata(L.) Pers., Phleum phleoides(L.) Karst., Poa angustifoliaL., Festuca valesiacaGaudin, Helictotri-chon pubescens(Huds.) Pilg., Bromopsis riparia (Rehm.) Holub., and Bothryochloa ischaemum(L.) Keng. The last species is dominant in places, forming local beard grass communities. Feather grasses (Stipa lessingianaTrin. et Rupr. and S. pennataL.) are rare, communities with their participation are small and have limited distribution. Stipa pennataL. is included in the Red Data Books of the Russian Federation and Stavropol krai (Krasnaya kniga…, 1998, 2002). How-ever, this species is not listed in the Red Data Book of the Kabardino-Balkar Republic (Krasnaya kniga…, 2000), probably because its distribution in the republic has not been studied sufficiently. According to Kos (1959), the vegetation of the Arik Ridge in the mid-20th century included one more feather grass species, Stipa pulcherrima(included in the Red Data Books of the Russian Federation, Kabardino-Balkar Republic, and Stavropol krai), but we have not found it on the slopes surveyed.

Ephemeral grasses such as Anisantha tectorum(L.) Nevski, A. sterilis(L.) Nevski, Bromus japonicus Thunb., and Poa bulbosaL. abundantly develop in spring. In trampled areas,Hordeum leporinumLink. is dominant.

Herbage is rich in species. The dominant group includes Salvia verticillataL.,S. tesquicolaKlok. et Pobed., Filipendula vulgaris Moench, Agrimonia eupatoriaL., Galium verticillatum Danth., Centaurea dealbataWilld., and Scabiosa ochroleucaL. Some communities also contain large proportions of Polygala anatolicaBoiss. et Heldr., Fragaria viridis (Duch.) Weston, Ajuga orientalisL., and Poterium polygamum Waldst. et Kit. Areas used as grazing grounds are often overgrown with Thymus marschallianusWilld. and the legume Onobrychis bobroviiGrosshm., which is hardly eaten by livestock because of abundant pubescence. An area of natural steppe vegetation with species rarely occurring in the republic and other red-list plants was discovered on the southwestern slope of the Arik Ridge 5 km east of the village having the same name (230 m a.s.l.). The floristic diversity of two communi-ties described there in a 10 ×10-m plot on May 25, 2006, reached 35 species in the herb–grass community and 39 species in the shrub–herb community. In both cases, the herbaceous layer had 85% coverage. The group of rare species consisted ofPaeonia tenuifoliaL., Asparagus verticillatusL. (another species of the genus,A. officinalisL., is more common), Dictamnus caucasicus(Fisch. et C.A. Mey) Grossh., Clematis lathyrifoliaBess. et Reichenb., Adonis flammeaJacq., Amygdalus nanaL., and some other plants.

The fern-leaved peony P. tenuifolia(Paeoniaceae) occurs in Prokhladnenskii raion of the republic, in typ-ical steppe habitats on the slopes of Dzhenali, Terek, and Arik ridges (Kos, 1959; Shkhagapsoev and Slonov, 1987; Krasnaya kniga…, 2000; our collections of 2006 from the Arik Ridge). The species is included in the Red Data Book of North Ossetia (Krasnaya kniga…, 1981), where it occurs along the Sunzha Ridge, and in the Red Data Books of the Russian Federation and Kab-ardino-Balkar Republic (Krasnaya kniga…, 1988, 2000). On the Arik Ridge, the average population den-sity of P. tenuifoliain the communities mentioned above is 7 ind./m 2 . In the same communities, single individuals of Bieberstein’s peony P. biebersteiniana Rupr. can be found. This species visually differs from P. tenuifoliain having broader leaf segments, and the dates of blooming and fruiting in these two species are also different. According to our observations, most P. tenuifoliaplants on May 16, 2006, already entered the stage of fruiting, while P. biebersteinianaplants were still blooming. It should be noted, however, that the taxonomic status of the latter species is ambiguous, since some botanists regard it as a subspecies of P. tenuifolia. In any case, it is listed as a true species in the Red Data Book of Stavropol Krai (Krasnaya kniga…, 2002).

Shrub communities consist mainly of Amygdalus nanaL. accompanied by Frangula alnusMill. and Rhamnus pallasiiFisch. et C.A. Mey. Communities described above contain no endemic species. Similar communities probably grow also on the Terek and Sunzha ridges but are absent in other regions of the republic. On this basis, such communi-ties may be classified as rare. The fauna of the region is poorly studied, and reli-able information on its present-day species diversity is almost absent. According to available data, large mam-mals are represented by the red fox and jackal. The ornithofauna includes the steppe eagle and small birds of prey; little bustard; among gallinaceous birds, quail; among passerines, the bee-eater Merops apiaster, which nests on ravine slopes.

Thus, the Arik Ridge is exposed to considerable anthropogenic impact: the major part of land is plowed, and most of the remaining part is under uncontrolled grazing load. In addition, population decline in some plant species (e.g., P. teniofoliaand feather grasses) is also explained by their commercial harvesting for dec-orative purposes. These factors are responsible for deg-radation of primary phytocenoses, expansion of weeds. and destruction of habitats favored by different species of the local fauna.

Thus, to conserve the steppe cenoses of the Central Caucasus within the Kabardino-Balkar republic, it is necessary (1) to establish a steppe nature reserve up to 10 000 ha in area on the Arik Ridge and (2) to include vascular plant species such as Stipa pennata, S. lessin-giana, Asparagus verticillatus, and Amygdalus nanain the Red Data Book of the republic.

The establishment of such a reserve will provide a basis for measures to restore populations of the little and great bustards, unique species of typical steppe ornithofauna that had been widespread in steppe eco-systems, including those of the Northern Caucasus.

In the mid-20th century, the little bustards used to nest on the Arik Ridge (A.N. Kudaktin, personal communi-cation) and the great bustard was recorded during the periods of flight and local winter migrations in the Cen-tral Caucasus (Beme, 1958).

Carbon Concentrations and Caloric Value of Organic Matter in Northern Forest Ecosystems

Key words: north, taiga, forest ecosystems, carbon, caloric value.

The data on the carbon content in different plant organs and their caloric value are necessary for evaluat-ing the bioproduction process in phytocenoses and for studying the carbon cycle and energy and mass exchange in forest biogeocenoses. According to published data, the carbon content in individual biomass fractions amounts to 50–57% of their dry weight in conifers and to 42–48% in deciduous woody plants (Risser, 1985; Kobak, 1988; Vogt, 1991). Most of researchers estimating carbon stock in forest communities assume that it accounts for 50% of the absolutely dry weight of trunk, roots, and branches and for 45–50% of the weight of green plant parts (Makarevskii, 1991; Bidsey, 1990; Uglerod v ekosiste-makh…, 1994; Tsel’niker and Malkina, 1994; Kobak, 1989; Isaev et al., 1993, 1996). The caloric value of plant components in the ecosystems of forest zone is better studied (Ovington, 1961; Golley, 1961; Kur-batskii, 1962; Molchanov, 1971; Kononenko, 1975; Dadykin and Kononenko, 1975; Dem’yanov, 1974, 1981; Ivask, 1983, 1985; Vookova, 1985).

Utkin (1986) thoroughly analyzed the available data on the caloric values of plants and animals. He found that the heat of plant combustion as a physical parame-ter is characterized by a relatively high variability, being dependent on plant species, growing conditions, morphological structure, age, period of sampling, and other factors. However, many aspects of plant differen-tiation with respect to their caloric value remain unclear. Special studies are necessary for elucidating the relationships between the heat of plant combustion and multiple environmental factors, the intensity of physiological processes, and the biochemical composi-tion of organic matter synthesized and accumulated by plants. Moreover, publications provide virtually no data on the carbon content and caloric value of organic mat-ter in forest ecosystems of the European Northeast. The purpose of this work was to determine the car-bon content and caloric value of different phytomass fractions. The following plants were studied: trees Pinus sylvestrisL., Picea obovataLedeb., Betula pen-dulaRoth., Populus tremulaL., and Larix sibirica Ledeb., Fl. Alt.; dwarf shrubs Vaccinium vitis-idaeaL., V. myrtillusL., and V. uliginosumL.; mosses Pleuro-zium schreberi, Hylocomium splendens, Polytrichum commune, and Sphagnumsp.; mixed herbaceous sam-ples including Trientalis europeaL., Maianthemum bifoliumL., Equisetum silvaticumL., and Agrostis tenuisSibth.; and lichens Cladinasp. The main compo-nents of plant fall and litter were also analyzed. The study was carried out in pine and spruce phyto-cenoses of the middle taiga subzone in the Komi Republic (62¡N, 50¡20′E). Plant samples for analysis were collected in the end of the growing period (August to September) simultaneously with estimating the phy-tomass of the plant communities. The carbon concen-trations in phytomass fractions were determined in an ANA-1500 automatic nitrogen and carbon analyzer (Carboro Erba, Italy); the caloric value, by the combus-tion method according to Kochan (1982). Measure-ments were made in ten biological and three to eight analytical replications. The experimental data were processed statistically by conventional methods. As follows from Tables 1 and 2, the range of carbon concentrations in different phytomass fractions of trees was 44.6–50.3% dry weight; in plants of the herb– dwarf shrub layer, 41.9–53.4%; in mosses and lichens, 42.3–45.4%; in forest litter, 45.8–48.2%; and in the components of plant fall, 44.6–53.1%. The carbon con-centrations in trees varied insignificantly: the coeffi-cient of variation (CV) was 2.4% for individual species and 1.5–4.3% for phytomass components within a spe-cies. The range of carbon concentrations in plants of ground vegetation was slightly higher, but the variation of this parameter by species did not exceed 10% in these plants and 2.8% in mosses and lichens. The car-bon concentrations in individual fractions of plant fall and different types of litter differed by 5 and 8.6%, respectively.

The analysis of data on the caloric value of tree plants shows that this parameter of individual phyto-mass fractions varied from 16.81 to 21.77 kJ/g in spruce, from 16.40 to 22.91 kJ/g in pine, from 17.91 to 21.56 kJ/g in larch, and from 16.66 to 20.95 kJ/g in birch (Table 3). The coefficients of variation were 10.3, 8.8, 7.0, and 5.2%, respectively. Higher energy values were typical of trunk wood and large roots. The caloric value of plants in the lower layers of coniferous communities varied from 17.44 to 19.76 kJ/g; of forest litter, from 17.37 to 18.46 kJ/g; and of plant fall, from 16.58 to 19.89 kJ/g. The variation in this parameter both in plants of ground vegetation and in the litter was insignificant: the coefficients of variation were 3.0 and 2.4%, respectively These data can be used for making up the energy and carbon balance and for studying energy flows in forest ecosystems of the taiga zone..

Geographic Trends in the Accumulation of Heavy Metals in Mosses and Forest Litters in Karelia

Heavy metals (HMs) are considered to be among priority technogenic pollutants. To solve ecological problems related to the environmental effects of HMs in the Russian North, it is necessary to make a detailed inventory of their contents in natural objects in different areas with regard to the diversity of climatic and soil-geochemical conditions and the degree of industrial development in these areas. It is known that mosses are informative indicators of aerotechnogenic environmen-tal pollution. Forest litters are important as the struc-tures retaining and accumulating various pollutants. The contents of HMs in the soil depends on the distance from local pollution sources and, to a large extent, on the pattern of pollutant transfer in the upper layers of the atmosphere. An important role belongs to region-specific natural factors, i.e., local climate, relief, vege-tation, and soils.

The Republic of Karelia is located on the Baltic shield, which forms the northwestern part of the Russian platform. The vast area of the republic (117300 km 2 )

extends from the north to the south for 672 km; hence, the climate, geological structure, hydrographic net-work, soils, and vegetation in different parts of the republic are heterogeneous.

The climate in Karelia is relatively mild, with a long mild winter and a short cool summer; considerable cloudiness, high humidity, and changeable weather are characteristic of all seasons. The prevailing form of atmospheric circulation over the territory of Karelia is the western transfer of air masses. The formation of precipitation is also accounted for by moisture evapo-rated from the White Sea and numerous lakes and bogs, which cover one-third of the Karelian territory. Vegeta-tion has a considerable effect on the migration of sub-stances. In Karelia, coniferous forests are the dominant type of vegetation.

The spectrum of possible sources of technogenic HM pollution in Karelia is wide. There are 10284 sources of industrial emissions into the atmosphere, and most of them are concentrated in the cities of Petrozavodsk, Segezha, Kostomuksha, and Kondo-poga. The total amount of emissions from large indus-trial enterprises of these cities reaches 128600 tons per year. A complex combination of technogenic factors and natural geochemical conditions in Karelia deter-mines the pattern of HM distribution over its territory. In this work, we studied green mosses (Pleurozium schreberi, Hylocomium splendens) and forest litters. The former indicate the state of the atmosphere over a relatively short period of time (approximately three years), and the chemical composition of the latter reflects the impact of long-term industrial pollution (over more than ten years). The chemical analysis of mosses and litters can provide information about the sources, ranges, and extents of environmental pollu-tion, as well as reveal major pollutants. Our studies were performed by internationally accepted methods (Atmospheric Heavy Metal…, 1996).

Samples of green mosses and forest litters were taken from test plots of the bioindication network cov-ering the entire Karelian territory. The contents of iron, manganese, chromium, copper, nickel, zinc, cobalt, lead, and cadmium in the samples were determined by atomic absorption spectrometry.

We also estimated the effects of climatic parameters (wind rose, precipitation rate) on the distribution of aerotechnogenic pollutants containing HMs over the territory of the republic. The data on each of eight wind directions recorded by the Karelian hydrometeorologi-cal observatory (N, S, W, E, NE, NW, SE, SW) was assessed quantitatively with respect to wind stability, i.e., the frequency of its occurrence as a percentage of the total number of observations (without calm winds). Taking into account wind directions in winter and sum-mer and different weather patterns in the cold or warm periods of the year, the parameters of stability were averaged. Thus, we distinguished cold winters with lit-tle snow from warm, snowy winters and cold, rainy summers from warm, dry summers.

To estimate the correctness of grouping (homogene-ity within each group and heterogeneity of different groups), stepwise discriminant analysis was used. Its results confirmed that all five groups were identified correctly: they proved to be internally homogeneous and did not overlap with one another. The main dis-criminators (major pollutants) in forming regional groups with respect to the pollution of mosses are nickel, cobalt, chromium, and cadmium. According to their significance for group formation, they can be arranged in the following series: Co > Cr > Ni > Cd. In the case of forest litters, the main discriminators arranged in the same order are as follows: Fe > Mn > Pb > Zn.

The results of pairwise comparisons of the regional groups in the three-factor spaces with respect to HM contents in mosses and forest litters (Table 3) demon-strated that differences were significant only for groups I and II, especially concerning the contents of cad-mium. In the second group (Segezhskii and Med-vezh’egorskii raions), differences between HM accu-mulation in mosses and forest litters were significant for the majority of elements (especially for copper) and nonsignificant for zinc and iron.

Thus, we revealed the existence of geographic trends in the distribution of pollutants over the Karelian territory and their accumulation in mosses and forest litters.

On the Problem of Assessing the Resistance of Planktonic Community to Adverse Influences

Key words: ecosystem, stability, planktonic community, seasonal succession of phytoplankton.

The increasing anthropogenic impact on natural ecosystems makes it necessary to study and forecast the ecological consequences of chemical pollution of the environment, including the hydrosphere. The ability of aquatic ecosystems to maintain homeostasis is limited, and a further increase in anthropogenic load may result in their irreversible transformation and degradation. The state and development of an aquatic ecosystem depend on a combination of different environmental factors, among which a major role belongs to pollution with heavy metals, pesticides, and petroleum products. Exposure to these pollutants may have different conse-quences, depending on the stage of seasonal succession in the planktonic community (Phillips et al., 1998; Mauser, 1998; Tarkpea et al., 1998). To prevent or reduce ecological damage, it is necessary to determine the periods when ecosystems are most vulnerable. This information is very important for estimating economic damage from accidental environmental pollution and determining the seasons in which industrial activities will be less hazardous in ecological terms. An impor-tant task of specialists in ecology, including aquatic toxicology, is to develop the concept of the assessment of critical changes in natural systems under the effects of anthropogenic factors.

PROBLEMS IN ECOLOGICAL TOXICOLOGY

Methods for assessing the vulnerability of biologi-cal systems at the ecosystem level have not yet been developed. Traditional toxicological methods based on the responses of individual test organisms to toxic action are not fully applicable to the natural communi-ties of aquatic organisms and whole ecosystems (Wun-dram et al., 1997; Molchanova et al., 1996; Shadrina, 1997). The responses of different taxonomic groups (species) of planktonic organisms to toxicants differ, and the general stability of the planktonic community varies depending on seasonal changes in both the com-munity structure and the functional activity of different groups of algae.

A feasible experimental approach to this task is to study the functioning of ecosystems under almost criti-cal conditions, i.e., at a concentration of toxicants in an aquatic medium that approaches a certain threshold, but where the changes they cause in the ecosystem are reversible. The concentrations exceeding this threshold cause irreversible changes and degradation of the planktonic community.

Phytoplanktonic organisms, as the main primary producers of organic matter in an aquatic ecosystem, are a key element providing for ecosystem stability. The conditions critical for the phytoplanktonic community are considered to be critical for the ecosystem as a whole. Therefore, it is essential to formulate the princi-ples of assessment of ecosystem resistance to chemical pollution as applied primarily to the phytoplankton. Seasonal succession in aquatic ecosystems has cru-cial transitional periods when one community replaces another, which actually determine the subsequent course of succession. If the impact of pollutants exceeds the above threshold at this transitional stage, irreversible changes will occur in the ecosystem struc-ture, and its development will follow a different path- way. For instance, the elimination of usual dominants and their replacement by more resistant forms of algae may take place. Thus, the concept of the critical level of impact should have reference to certain periods in the development of communities and the ecosystem as a whole.

Corresponding ecological changes may upset the balance between the synthesis and decay of organic matter in the planktonic community and organic matter flows. Under certain conditions, a great amount of readily assimilable organic matter released due to the death of planktonic organisms may stimulate an explo-sive growth of mixotrophic algae and, in some cases, lead to the so-called red tides observed in different areas of the World Ocean.

MAIN APPROACHES

To forecast the ecological consequences of pollution of the aquatic environment, it is necessary to estimate ecosystem resistance to adverse influences during the crucial biological periods. This involves the determina-tion of the critical concentrations of pollutants affecting basic ecological parameters. For the phytoplankton, these parameters include primary organic matter pro-duction (P), total biomass (B), species composition, destruction (D), coefficients P/Band P/D, and the abun-dance and biomass of the main groups of algae. The ecosystem responds differently to adverse envi-ronmental influences in different periods (seasons of the year), depending on the state of ecosystem compo-nents (the concentration of biogenic elements, the spe-cies structure of communities, conditions of illumina-tion, etc.). The pattern and geographic features of sea-sonal changes in the degree of ecosystem stability are virtually unknown. The experimental–analytical approach to the assessment of stability of freshwater planktonic communities under stress is as follows.

In the course of seasonal succession in the phy-toplankton, there are periods characterized by different degrees of its resistance to a certain adverse external influence. This is explained primarily by differences in the resistance of individual structural components of the phytoplanktonic community in a given period of time. To determine the most vulnerable periods in the development of the planktonic community, it is neces-sary to perform simultaneous observations providing data on the stage of seasonal succession, dominant algal species in the community, and the responses of phy-toplankton to standard influences (for instance, pollut-ants added at certain doses). In addition, model ecoto-xicological experiments are necessary for determining the range of concentrations and combinations of pollut-ants that are critical for the given community. Only the sum of these data can provide a reliable basis for ana-lyzing the dynamics of resistance of the planktonic community to adverse influences and predicting its behavior in stress situations taking place in different periods of the biological season.

Special attention should be paid to the response of the phytoplanktonic community to the anthropogenic impact in the aforementioned crucial periods that deter-mine the subsequent stages of succession. To identify such periods, it is necessary to analyze natural seasonal changes in aquatic ecosystems and distinguish the phases of community development differing in the structure and composition of dominant species, the content of biogenic elements, and the background con-centrations of pollutants. The vulnerability of the phytoplankton in the crucial periods identified in this way may be estimated in an ecotoxicological experiment. In such experiments, the response of phytoplankton to different concentrations of toxic agents is evaluated by parameters such as pri-mary production, live release of organic matter, species composition, and biomass. They are performed with natural species complexes (in microcosms) under quasi-in situ conditions. Comparison of phytoplankton responses to the impact of toxic concentrations of pol-lutants at different stages of succession makes in possi-ble to reveal the most vulnerable periods (Dallakyan et al., 1999). In these experiments, toxicants are added only as standardized adverse factors causing certain community responses. The response of the phytoplank-tonic community to concrete concentrations of pollut-ants are not considered in this case. Along with experi-mental studies, field observations on the current state of ecosystems, including hydrological, hydrochemical, and biological parameters, are performed.

When short-term experiments based on the dose– effect principle are aimed at comparing the responses of different communities to the same factor, rather than estimating the toxicity of a certain substance, it is only important to perform all series under the same condi-tions, whereas the requirement for their correspon-dence to natural conditions loses its validity (Lifshits and Korsak, 1988). Such experiments provide the pos-sibility of ecotoxicological sounding of aquatic ecosys-tems with the purpose of revealing differences in the adaptation potentials of different communities (on a geographic or temporal scale). This approach implies the careful selection of biological indices responding to toxic exposure, which must satisfy the following requirements: (1) the index must be integrated, i.e., reflect the state of the entire ecosystem or of its most important part; and (2) its changes under the effect of toxic agents must be rapid and consistent. Comparing the results obtained in different areas, it is possible to estimate the sensitivity of ecosystems and trends in its changes in the crucial periods of plankton succession.

ANALYSIS OF THE COMBINED EFFECT OF ADVERSE FACTORS

At the next stage, experiments are performed to study the combined effects of environmental factors. It is known that pollutants in water can interact in a com-plex way with different abiotic components, and their toxic effect in each particular case depends on a variety of conditions (water temperature, its chemical compo-sition, etc.). Therefore, these model experiments should be performed under conditions close to those in a natu-ral water body and according to a certain plan that involves a quantitative assessment of the interaction of factors under study.

The purpose of complete factor experiments (CFEs) in ecotoxicology is a quantitative analysis of the com-bined and independent effects of toxic agents at several concentrations and in different combinations on biolog-ical objects (Maksimov et al., 1969). As a rule, CFEs are performed with two or three agents (factors) at three concentrations (CFE 3 2 or CFE 3 3 , respectively), with each combination studied in an individual experimental series. The correct range of factor values (e.g., effective concentrations of a toxicant) for CFE is determined in preliminary dose–effect experiments. It is convenient to represent the results of CFEs as diagrams of response surfaces that reflect changes in the test parameter (e.g., primary production or biomass of the phytoplankton) depending on the combination of factors (Fig.1). Regardless of the extreme diversity of biological objects, the strength of response observed in dose– effect experiments with a single species directly depends on the strength of impact: the more toxic the environment created in the experiment, the more severe the disturbances in biological processes. Conversely, such a trend is usually not observed in experiments with multispecific systems or in the course of observations on the pattern of responses in nature (Korsak and Nakani, 1976). This can only be attributed to the effect of the compensatory resources of ecosystems.

Observations of the ecological state of water bodies and the results of biocybernetic investigations provide evidence that the response of an ecosystem to toxic exposure has two phases. At the first phase, when the toxic impact is not very strong, unspecific physiologi-cal–biochemical compensatory mechanisms begin to operate. No profound rearrangement of the species structure of the ecosystem (such as the extinction of individual species or the change of dominants) takes place, and adverse effects on the ecosystem as a whole or on any process occurring in it are compensated due to the quantitative changes in the rate of metabolic pro-cesses in individual groups of organisms (in phyto-plankters, for instance, exposure to pollutants leads to changes in the rate of photosynthesis, the amount and pattern of excretions, membrane permeability, etc.). In general, the unspecific response of the ecosystem to the inhibition of individual biological processes has the same pattern as in the case of experiments with groups of conspecific organisms.

At the next phase, as the concentration of pollutants or the period of exposure increase, the species structure of the ecosystem begins to change. The species less sensitive (more resistant) to the corresponding influ-ence gain dominance in individual components of the ecosystem, and its total species diversity decreases. Both physiological and ecological compensatory mechanisms operate in this period, and the ecosystem response has a more complex and diverse pattern. When the impact becomes still stronger, it overpowers the resistance of the ecosystem and causes irreversible changes in it, which are so profound that they may lead to its degradation and eventual destruction. The species composition at this phase is impoverished, and inter-specific compensatory rearrangements are insignificant (Korsak et al., 1976; Maksimov et al., 1985).

Thus, the level of toxic exposure that causes the sec-ond phase of response involving specific ecological compensatory mechanisms is critical for the ecosys-tem. The monotonic pattern of ecosystem response is disturbed, with the points of inflection of one-dimen-sional and multidimensional response surfaces corre-sponding to the critical concentrations of toxicants.

Their range can be determined by comparing the stan-dard (reference) and the experimental response sur-faces and identifying the zone in which they do not coincide. These concentrations are indeed critical, since they indicate the limit of toxic exposure that can-not be exceeded without causing irreversible distur-bances in the structure and functioning of the ecosys-tem. The geometric analysis of response surfaces obtained in the course of factor experiments makes it possible to analyze the complex processes involved in the reactions of planktonic communities to the anthropogenic impact. The ecological–analytical comparison of the response surfaces of natural communities with a standard (reference) surface may be instrumental in determining the resistance of the planktonic commu-nity to an adverse impact and estimating potential crit-ical changes in the ecosystem structure (Maksimov et al., 1989). In practice, to determine the degree of cor-respondence between the experimental and standard-ized surfaces, it is necessary to calculate the coefficient of orderliness of the response surface (CORS), i.e., the ratio of the number of cases deviating from the standard to the total number of concentrations compared. This index characterizes the ecological profundity of the community response and allows specialists to supple-ment a purely descriptive analysis of the results of a factor experiment with quantitative data. In the case of purely physiological, unspecific responses, CORS = 0; if all possible combinations of concentrations induce only ecological responses, CORS = 1 (Maksimov et al., 1989).

Thus, we can determine the limits of the critical con-centrations of pollutants (or other adverse factors) by comparing the response surface obtained in experi-ments with a true multispecific system and the response surface characterizing a monospecific system in which only unspecific, physiological compensatory mecha-nisms operate. For the standard response surface, the following trend was revealed in numerous experiments (Nosov et al., 1981; Dallakyan et al., 2002): the stron-ger the impact, the more intense the adverse response of the system (mortality increases, and biological pro-cesses are inhibited to a greater extent). We used the dose–effect approach in studies on the toxic influence of copper on primary phytoplankton production in the Ucha Reservoir, which included sev-eral series of ecotoxicological experiments with the natural phytoplanktonic community performed in dif-ferent periods of its seasonal development. The results of one series are presented in Fig. 2. They show varia-tion in the sensitivity of production capacities of the phytoplankton in the course of seasonal succession, when considerable changes in abundance and the replacement of main dominant groups (diatoms and blue-green algae) took place. It is apparent that the phy-toplankton was most resistant to the toxic effect of cop-per in the periods of its greatest abundance and highest total primary production. However, note that specific production (i.e., primary production related to the total phytoplankton abundance) was minimal in these periods. These results provide a basis for the conclusion that transitional periods in the seasonal phytoplankton suc-cession may be the most sensitive to adverse factors. However, basic trends in the effects of certain factors (for instance, heavy metals) on the structural and func-tional characteristics of phytoplankton require further investigation, namely, into their combined action, using the principles of the factor experiment.