Species composition and structure of macrozoobenthos in Lake Sevan during the period of its increased water level

A list of macroinvertebrate species recorded in the zoobenthos in Lake Sevan in 2007 and 2010 is presented. The list includes 38 species, 14 of which have been found in the lake for the first time. Chironomid larvae and pupae are the most diverse (27 species) in the macrozoobenthos of the lake. In Bolshoi Sevan, the maximum biomass of macrozoobenthos (24.82 g/m²) was recorded in the sublittoral; in Malyi Sevan the maximum biomass (14.31 g/m²) was recorded in the profundal. In 2010 chironomids dominated by biomass in the sublittoral (48.9 and 60.3%, respectively). The benthos in the littoral was dominated by oligochaetes (50.2%).     

Chironomids fauna (Diptera, Chironomidae) in some waterbodies and watercourses of Mongolia

An annotated list of chironomid species from some waterbodies and watercourses of Mongolia identified by an imaginal developmental stage is presented. The list includes 97 species of 39 genera and 5 subfamilies: Tanypodinae (6 species), Diamesinae (1), Prodiamesinae (2), Orthocladiinae (33), and Chironominae (55). Of all found chironomid imagos, 11 species have been earlier identified for the Mongolian fauna, the other 86 species have been registered for the first time. The largest number of species has been recorded in Lake Sangiyn-Dalai—28; in Lake Ugiy and River Ider—19 species. In the rest of the lakes, the number of recorded species varies from 18 to 10 species, and in rivers, from 13 to 2. Most of the species are boreal and widespread. The number of Paleoarctic species amounts to 44 and Holarctic species amounts to 49.     

Features of Structural Changes in the Plankton Community of an Alpine Lake with Increasing Fish Density in Summer and Autumn

Biology Bulletin - It is found that a large species of the order Cladocera, Daphnia (Ctenodaphnia) magna Straus, has disappeared from the zooplankton composition in the alpine Lake Sevan, Armenia,...     

Zooplankton in Lake Sevan during the period of high water level and low fish density

It is shown that, upon the flooding of ephemeral waterbodies in the coastal region and the formation of new warmer sites of the shoals due to the rising water level in Lake Sevan in 2011, species typical for temporary waterbodies and various shoals have been recorded in the zooplankton. Among them, Daphnia (Ctenodaphnia) magna Straus reached mass development, which was favored by the minimal control from “the top” and favorable trophic conditions. Owing to the abovementioned factors, the total lake zooplankton biomass and water transparency increased. The uneven distribution of D. (C.) magna was determined by the density of fish that prefer it as food.     

Changes in autumn zooplankton in the pelagic zone of Lake Sevan (Armenia) during the increase in fish abundance

The qualitative composition and structure of the autumn zooplankton in the pelagic zone of Lake Sevan in years that were characterized by different abundancies of fish are described. In October 2013, upon the increase in whitefish abundance, the species richness of zooplankton increased insignificantly; the values of the trophic coefficient and the Shannon index, calculated by the number, increased; and the specific number of Rotifera and Cladocera decreased. At the same time, atypical changes were recorded in the development parameters of zooplankton invertebrates. They were expressed as an increase in the total biomass due to Cladocera, among which large Daphnia (Ctenodaphnia) magna Straus occupied the leading position. The possible reasons for the particular changes in zooplankton are discussed.     

Discrete Modeling of Dynamics of Zooplankton Community at the Different Stages of an Antropogeneous Eutrophication

Mathematical modeling is a convenient way for characterization of complex ecosystems. This approach was applied to study the dynamics of zooplankton in Lake Sevan (Armenia) at different stages of anthropogenic eutrophication with the use of a novel method called discrete modeling of dynamical systems with feedback (DMDS). Simulation demonstrated that the application of this method helps in characterization of inter- and intra-component relationships in a natural ecosystem. This method describes all possible pairwise inter-component relationships like “plus–plus,” “minus–minus,” “plus–minus,” “plus–zero,” “minus–zero,” and “zero–zero” that occur in most ecosystems. Based on the results, a working hypothesis was formulated. It was found that the sensitivity to weak external influence in zooplanktons was the greatest during the mid period of eutrophication in Lake Sevan, whereas in the final stages of eutrophication, an outbreak in the biomass production of cyanobacteria was evident. To support this approach, a weak external disturbance in the form of magnetic storm was used to see its effect on species Daphnia longispina sevanica. A statistically significant correlation between the frequency of magnetic storms and the number of this species was revealed and an increase in the number of toxic cyanobacteria species as a consequence of eutrophication. This paper, for the first time, suggests a DMDS method, to diagnose impact of anthropogenic eutrophication on environment.     

Population dynamics of Potamothrix alatus paravanicus Poddubnaya & Pataridze (Tubificidae) in different areas of Lake Sevan

Potamothrix alatus paravanicus Poddubnaya & Pataridze (Tubificidae) is the most abundant species of benthic invertebrate in Lake Sevan and the only species in the deep profundal. Differences in annual temperature, length of the stratification period (low oxygen content) and bottom sediment characteristics influence the population of P. a. paravanicus in different depth zones of Lake Sevan. From shallow to deep water a regular increase of the following indices was observed in 1984–1987: annual biomass from 1.2–2.0 to 8.2–17.0 g m^–2 wet weight; mean individual wet weight of clitellate specimens from 2.0–3.8 to 8.3–16.6 mg; total life span from one and a half to more than 20 years; the length of breeding season from 2–3 to 12 months.An important ecological distinction between P. a. paravanicus and allied Potamothrix hammoniensis (Michaelsen) is the much lower fecundity of the former species.     

Where ichthyofaunal provinces meet: the fish fauna of the Lake Edward system,East Africa

Based on literature, museum collections and three recent expeditions, an annotated species list of the Lake Edward, East Africa, drainage system is presented, excluding the endemic haplochromines. A total of 34 non-Haplochromis species belonging to 10 families and 21 genera are recorded from the system. Three of these are endemic and two others have been introduced in the region. Six species are new records for the Lake Edward system. A species accumulation curve indicates that we probably covered most of the non-Haplochromis species in the area sampled during the recent expeditions, but undetected species might still be present in the Congolese part of the system, which is poorly sampled. A comparison of the species list with those of neighbouring basins confirmed the placement of the Lake Edward system within the east-coast ichthyofaunal province.     

Studies on the moss mites of Snowdonia (Acari: Oribatei). 2. The Cnicht

A faunal list of oribatid mites collected from the summit of the Cnicht, Snowdonia, at 2265 ft is given, together with critical notes on the taxonomy and distribution of several of the species. The list provides further evidence of the presence of arctic-alpine and European-alpine species of Oribatei on the mountain peaks of Britain. A comparison of the faunal list with lists of species recorded by the author on another peak in Snowdonia and on high ground in other parts of Britain (Peak District, Lake District) and by Block in Westmorland, provides evidence of a group of additional species which can be regarded as characteristic of upland areas in general of Britain and Europe.     

Assessment of Possible Causes of Changes in Аbundance and Sexual Structure in Populations of Prussian Carp (<Emphasis Type="Italic">Carassius auratus gibelio</Emphasis> Bloch., 1783)

The prevalence of processes of the increase in abundance and changes in the sexual structure of Prussian carp populations in waterbodies differing dramatically in ecological properties and distant from each other (Lake Sevan and Rybinsk Reservoir) indicates the presence of global factors affecting climatic zones. The increase in environmental temperature due to global warming may be such a factor. Experimentally proven high thermophilicity and the thermal stability of Prussian carp, as well as its low sensitivity to hypoxia, provide some advantages for this species over many other fish inhabiting the same waterbodies.     

Specific features of the zooplankton of the coastal zone of Lake Sevan

Specific features of the Lake Sevan zooplankton development during a rise in water level in July 2007 and a change in the fish density were revealed. Compared to earlier data (from the second half of the 20th century), the pelagial zooplankton quantitatively dominates over the zooplankton of shallows. It is shown that the diversity and abundance of rotifers increase in the coastal zones subject to inundation. The rotifer indicator species of eutrophic and α-mesosaprobic waters contribute to this increase. The stimulating effect of the waste products of a bird colony on the zooplankton of the lake shallows is revealed.     

Chironomidae (Diptera) from light catches on the man-made Volta Lake in Ghana

Summary A list of chironomid species is provided for the Volta Lake in Ghana, a man-made lake in tropical West Africa which started to fill in 1964. Insects were attracted to lights on the research vessel Tilapia at six different stations from 1966 to 1968. From the 25,128 specimens collected, 45 species were identified. 21 species are recorded for the first time in Ghana. The most abundant species are: Nilodorum fractilobus, Chironomus formosipennis and Nilodorum brevibucca. The larger number of species occurring in the transitional river-lake zone, compared with the Lake itself, is discussed in relation to the changes in the environment during each year as a result of the alternating dry and rainy seasons.     

Parthenites and cercaria of trematodes in the snails Lymnaea saridalensis (Gastropoda, Pulmonata), which inhabits the watershed area of Chany Lake (the South of Western Siberia)

The full list of parthenogenetic larvae and cercaria is presented for the first time for the freshwater snail L. saridalensis (Gastropoda, Pulmonata), which inhabits the watershed area of Chany Lake. It was found that this snail species plays a significant role as the first intermediate host in the life cycles of trematodes in the southern part of Western Siberia. The invasion parameters were calculated for different parasite species. It was found that 50% of the L. saridalensis population serves as the first intermediate host for eleven trematode species that belong to six families: Plagiorchiidae, Echinostomatidae, Diplostomatidae, Strigeidae, Notocotylidae, and Schistosomatidae. The prevalence of infection by each trematoda species in L. saridalensis was determined. Five species of trematodes from the Plagiorchiidae and Echinostomatidae families formed the center of the parasite community, viz., the species Plagiorchis elegans, P. mutationis, Opisthioglyphe ranae, Molinella anceps, and Echinoparyphium aconiatum. Two species, Plagiorchis mutationis and P. multiglandularis, were recorded in the studied area (the Chany Lake watershed area) for the first time at the stages of parthenite and cercaria. It was also found that 1% of L. saridalensis population have multiple (mostly two-species) infections.     

Variation of mini- and microsatellite DNA markers in populations of parthenogenetic rock lizard Darevskia rostombekovi

Variation and clonal diversity in populations of the parthenogenetic rock lizard Darevskia rostombekovi was examined by means of multilocus DNA fingerprinting using mini- and microsatellite DNA markers M13, (GATA)4, and (TCC)50). The animals examined were shown to exhibit a clonally inherited, species-specific pattern of DNA markers (fingerprint profile) that is different from the species-specific patterns of parthenogenetic species D. dahli, D. armeniaca, and D. unisexualis. The mean intraspecific similarity index S was 0.950 (0.003) for a sample of 19 animals from three isolated populations of North Armenia. This significantly differed from the estimate of this parameter for a sample of 21 animals including two individuals from mountainous, relict population from the vicinity of the Sevan Lake, which was equal to 0.875 (0.001). A comparison of DNA fingerprints showed differences between 21 individuals attaining 79 DNA fragments of 1801 mini- and microsatellite markers included in the analysis. The results obtained show that intraspecific variation in D. rostombekovi is higher than that in the previously studied parthenogenetic species D. dahli (S = 0.962) and D. unisexualis (S = 0.950) (P < 0.001). Taking into account that D. rostombekovi is considered monoclonal on the basis of allozyme data, the problem of clonal variability is discussed with regard to the evidence on nuclear DNA markers. It is suggested that the hybrid karyotype of D. rostombekovi, which is more unstable than that of D. dahli and D. unisexualis, generates a series of chromosomal rearrangements (mutations). This may lead to the appearance of a geographically isolated chromosomal race (clone) in the population inhabiting the southeastern coast of the Sevan Lake.     

白洋淀原生动物群落多样性变化与水质关系研究

报道了大型浅水型湖泊原生动物群落变化与富营养化关系的研究,通过对华北平原最大淡水湖-河北白洋淀两个湖区9个采样站的初步调查,共鉴定出77种原生动物,其中43种为该湖首次记录：利用PFU原生动物群落结构和功能方法快速（两次实验的群集速度均为1d时间）监测了不同湖区的水质状况,水质分析及原生动物定性和定量调查结果表明,湖区Ⅰ（安州至枣林庄5个采样点）水体的污染程度明显大于湖区Ⅱ（圈头至端村4个采样站）,通过与20世纪50年代的调查资料比较,较好地反映了白洋淀富营养化的发展趋势。     

Patterns of the quantitative distribution of plankton heterotrophic flagellates in the high-mountain Lake Sevan (Armenia)

Patterns of the quantitative development and spatial distribution of heterotrophic flagellates have been studied in Lake Sevan (Armenia). The abundance and biomass of flagellates is lower in summer than in autumn, but on the whole these parameters correspond to the quantitative parameters in oligotrophic lakes. Differences in the vertical and horizontal distribution of flagellates have been found during summer stratification and autumn homothermy.     

Initial Stage of Macrozoobenthos Formation in Reservoirs of Western Mongolia

Data on the initial stage of macrozoobenthos formation in the Taishir and Durgun reservoirs in western Mongolia in 2010–2015 have been generalized. A taxonomic list of macrozoobenthos is presented; 15 species have been recorded in Mongolia for the first time. In the Durgun Reservoir, the formation of bottom sediments and communities of invertebrates in the near-dam part is accelerated due to the water-flow transport of reed beds and invertebrates from Lake Khar-Us. The macrozoobenthos in the Taishir Reservoir is formed first due to consumers of terrigenous organic matter (decaying terrestrial vegetation and soils), and then by inhabitants of sapropelic mud; complexes of filter feeders, Spongilla lacustris (L.), are formed in the profundal zone. The process of macrozoobenthos development in the reservoir is similar to that in lowland reservoirs. After the construction of the reservoir, quantitative characteristics of macrozoobenthos increased downstream of the dam in the Dzabhan River and rheophilic species were replaced by limnophilic ones.     

Annotated checklist of the leech species diversity in the Maloe More Strait of Lake Baikal,Russia

In this paper, the very first checklist of the freshwater leeches of Maloe More Strait, a special part of Lake Baikal, is presented. It includes 14 free-living and parasitic species, of which four species belong to endemic Baikal genera – two species from Baicalobdella and one species each from Baicaloclepsis and Codonobdella. The checklist highlights six potentially new morphological species recorded for the first time in the area. The exact systematic position is stated for all leech species. Each species from the list is provided with information on taxonomic synonymy, data on its geographic distribution, and ecological characteristics. New species records are additionally provided with brief morphological characteristics and photos of their external morphology.     

The Upper Palaeolithic site of Kalavan 1 (Armenia): An Epigravettian settlement in the Lesser Caucasus

The open-air site of Kalavan 1 is located in the Aregunyats mountain chain (at 1640 m above sea level) on the northern bank of Lake Sevan. It is the first Upper Palaeolithic site excavated in Armenia. Led by an Armenian-French team, several excavations (2005–2009) have revealed a well preserved palaeosoil, dated to around 14,000 BP (years before present), containing fauna, lithic artefacts, as well as several hearths and activity areas that structure the settlement. The initial studies enable placement of the site in its environment and justify palaeoethnological analysis of the Epigravettian human groups of the Lesser Caucasus.