Vol 9, No 2 (2016)

Systematics of the three modern sections of the subgenus Rohrbachia of the genus Typha (Typhaceae) and reconstruction of evolution in different geological periods of the Cenozoic Era in Eurasia have been examined. The section Minimae was formed in the Paleogene (Eocene) on littorals of the Angarida–Beringian area; the sections Turanicae and Mongolica were formed on the border of the Paleogene–Neogene in Central Asia (Middle Asia, North China, and Manchuria).

The parameters of the photosynthetic activity per unit of the phytoplankton biomass have been studied for the reservoirs of the Volga River. The wide range of variability is accompanied by most of the values of A/B ratio laying within 0.5–3 mg O₂/(mg · day); the P/B ratio in the photic layer varies as 0.5–3 day^–1 and in the whole water column varies as 1 day^-1. The maximal values have been observed for the reservoirs located in the Upper Volga River. The turnover period of the phytoplankton biomass in the photic zone of the studied reservoirs was 0.2–1.6 day, or in2.1–3.8 times higher than for the whole water column from the surface down to the bottom. The seasonal variability of the A/B and P/B ratios in each reservoir had more pronounced individual variability than the variability observed for the whole cascade during the summer season. The A/B and P/B ratios decrease significantly in the oligotrophic waters to the eutrophic; these ratios have an indicator value.

The spatial variability of the vertical structure of bioluminescence intensity has been studied along the Crimean coast in the spring period. The location of a layer with a high intensity of bioluminescence has been determined and its dependence on hydrological characteristics and thermohaline structure of waters is shown. Structurization of the spatial variability of bioluminescence intensity has been made. Four regions that are distinguished by the pattern of the vertical distribution of the bioluminescence intensity have been distinguished in coastal waters of the Crimean Peninsula.

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.

The taxonomic composition and development level of macrozoobenthos in the Gilevsk Reservoir and the Alei River, as well as down- and upstream the reservoir, have been described. The dominant taxa of benthic invertebrates have been identified. The water quality of the studied objects has been estimated using the methods of bioindication based on the composition and structure of macrozoobenthos.

The specific features of rheoreaction in roach Rutilus rutilus (L.) larvae from open and protected shallows of the Rybinsk Reservoir have been studied. Data on length and weight of roach sampled at various habitats at B–E developmental stages are presented. It has been revealed that the type of roach larvae rheoreaction is a behavioral mechanism of their distribution over different types of habitats, not only in rivers but also in the waterbodies with slow water turnover rates—lakes and reservoirs. By the time of developmental stage E, this mechanism provides the sustainable spatial separation of juvenile fish, which in the future may lead to intrapopulation differentiation in roach.

The duration of sperm motility in four whitefish species in the Ob–Irtysh basin, namely, Coregonus tugun, the river and lake forms of C. peled, C. lavaretus pidschian, and C. nasus, has been studied. It is shown that the duration of sperm motility in these species has a statistically significant inversely proportional dependence on the temperature of the water that is used for activation. The total duration of sperm motility at the spawning temperature in the range from 0.1 to 5.0°C amounts to 331 ± 107 s, on average, while the duration of forward movement amounts to 149 ± 44 s, on average. At temperatures that exceed the spawning values (above 7.1°C), these parameters constitute 190 ± 47 and 86 ± 15 s, respectively. The highest interspecific variability in the duration of sperm motility was observed within the temperature range from 0.1 to 2.5 and above 7.1°C. C. tugun shows less dependence of the duration of sperm motility on temperature than the other species under study. At a temperature of 0.7°C, the total duration and duration of the forward movement of C. tugun sperm are 201 and 108 s, respectively. When the temperature was increased to 13.4°C, these parameters decreased by 1.2 and 1.1 times only, i.e., to 172 and 100 s, respectively.

The results of long-term investigations (1994–2012) of an infection rate of trematodes of the family Notocotylidae Lühe, 1909 in the first intermediate hosts (Bithyniidae family) are discussed. The bithyniid snails (11348 Bithynia troscheli (Paasch, 1842) and 4347 Bithynia tentaculata (Linne, 1758) in 1994–2012 from Western Siberia have been studied. Parthenitae and cercariae of the family Notocotylidae belong to three species: Notocotylus imbricatus Looss, 1894, Szidat; N. parviovatus Yamaguti, 1934 [syn.: N. chionis Baylis, 1928] and Catatropis verrucosa (Frohl.) Odhner, 1905. The extensiveness of infection of bithyniid snails by the tre-matodes (parthenitae and cercariae) of the family Notocotylidae in rivers basin Ob, Irtich, Karacyk and Chany Lake is analysed. The level of the infection of bithyniid snails by trematodes (parthenitae and cercariae) does not exceed one percent in different reservoirs. The similar data have been obtained during long-term studies in the estuare of the Kargat river, and in the Ob river (near Novosibirsk). The percentage of infected B. tentaculata was significantly higher than of infected B. troscheli in the total (1.79 and 0.32% accordingly, χ² = 95.1, p < 0.001), and in different reservoirs, too. The infected bithyniid snails are recorded in waterbodies of all four basins only in steppe (0.52 ± 0.37%) and forest-steppe zones (0.76 ± 0.07%). Bithyniid snails from waterbodies of the forest zone of the West Siberian Plain were not infected with parthenitae and cercariae of the family Notocotylidae.

This study assesses the comparative sensitivity and possibility of obtaining fast results of various methods of biotesting for several surfactants: Tween 85, sodium dodecyl sulfate (SDS), Fairy dishwashing gel, and Mif washing powder. The following test organisms are used for the study: luminescent bacteria Photobacterium phosphoreum (Beijerinck), preparation of Ecolum luminescent bacteria, unicellular algae Scenedesmus quadricauda (G.M. Smith), infusorian Paramecium caudatum (Ehrenberg), and crustacean Daphnia magna (Straus). It has been revealed that Fairy dishwashing gel possesses the strongest toxicity against the studied test objects. Daphnia and algae are most sensitive to the effects of Fairy and SDS, protozoan and luminescent bacteria are most sensitive to SDS, and Ecolum is most sensitive to Mif washing powder. The tested aquatic organisms and Ecolum are most tolerant to the effect of Tween 85.

In this paper we present modern approaches to the classification of hydrobiological samples based on various metrics of species-structure similarity—Euclidean distance, Renkonen index, and the cosine of the angle between the species abundances vectors. We use the cophenetic correlation coefficient, Gower distance, and Shepard-like plot for the justification of clustering method. For the choice of the optimal number of clusters, we apply approaches based on silhouette widths and binary matrices representing partitions. An analysis of the spatial structure of zooplankton communities in the small Linda River shows that average agglomerative clustering is an optimal algorithm for objects of this type. A comparative analysis of the results of cluster analysis on the basis of different similarity metrics shows that the most adequate classification can be obtained using the cosine of the angle between the species abundances vectors and the Renkonen index, whereas the classification based on the Euclidean distances is less successful from the biological point of view. Approaches outlined in this paper allow researchers to make quantitative decisions about key elements of classification, greatly reducing the subjectivity of the cluster analysis results.