Vol 12, No 3 (2019)

A mass-balance model simulating a biotic energy flow in the plankton community with the participation of microbial organisms has been designed for a lake-type ecosystem. The input abiotic parameters of the model are latitude, mean depth, water color, and total phosphorus content in water. The model was constructed on the basis of the data published for the Rybinsk Reservoir and Mongolian lakes. An analysis of the model indicated that the addition of the microbial loop to the traditional linear trophic chain resulted in a twofold decrease in the biomass and production of metazoan plankton and planktivorous fish. The value of the final ecosystem production (fish production) is suggested to be closely associated with the degree of development of the microbial loop during the growing season.

An electron microscopy study of phytoplankton from watercourses and water bodies on the Taz Peninsula (mainly the basins of Poilovayakha, Nyudya-Adlyurepoko, and Mongoyuribei rivers) makes it possible to significantly broaden the taxonomic spectrum of Bacillariophyta at the genus and species level—from 181 taxa from 28 genera to 338 species and intraspecific forms from 62 genera. A total of 25 species and varieties new for the flora of Russia are detected; 36 forms from 17 genera are identified only to the genus. The maximum taxonomic variability is recorded in the upper reaches of the Sobetyakha River (106) and in a nameless lake in the lower reaches of this river (91). The following species are the most widespread in the water objects under study: Tabellaria flocculosa, Neidium ampliatum, Achnanthidium helveticum, Nitzsсhia alpina, and Pinnularia sinistra.

New habitats of the Ponto-Caspian cladoceran Cercopagis pengoi in the Tetyushi, Ulyanovsk, Volga-Kama, and Kama reaches of the Kuibyshev Reservoir; the upper part of the Votkinsk Reservoir; and the lower part of the Kama Reservoir (near the city of Perm) are revealed by comprehensive studies performed at the water reservoirs of the Volga and Kama Rivers in summer 2015 and 2016. The northernmost find of the invader species was recorded in the Kama River near the town of Dobryanka (58°26′ N); thus, the species was found ≥3° further to the north in the Kama River than in the Volga River (54°57′ N). The species inhabited the uppermost 5-m water layer and the typical C. (С.) pengoi form represented the species in all the water bodies. In August, Juveniles and parthenogenetic females (body length 1.2–2.0 mm) with 2–7 embryos were observed in the water bodies, and single finds of males were made. The population size of the invader species (≤100 ind/m³) was comparable to that of the taxonomically similar hybrid form of the genus Bythotrephes (B. brevimanus × B. cederströmii) that inhabits the same areas as C. pengoi does. The routes of dispersal and the distinctive features of the spatial distribution and ecology of the species are discussed.

The macrozoobenthos have been studied in 14 taiga lakes characterized by different contents of heavy metals and oil products (OPs) in the bottom deposits (BDs) (from slightly polluted to extremely polluted). Sixty-five invertebrate species and taxa (the rank below the genus) have been registered. Chironomids dominate in regards to species diversity and frequency of occurrence in most studied lakes. The faunistic similarity of the surveyed lakes in terms of the Sørensen–Chekanovsky index vary from 10 to 63%. The inhibition of benthic communities is not observed in the group of lakes with an extreme content of OPs. The dominant complex comprises Oligochaeta, Mollusca, and Chironomida. The Matkovskii index does not exhibit a significant difference of this group of lakes from the lakes with background conditions. No significant correlations are found between the structural parameters of macrozoobenthos (total number of species and number of species in taxonomic groups) and the content of the OPs, but they have been observed for heavy metals.

The effect of different concentrations of NaCl on photosynthetic parameters and structural components of membranes of Hydrilla verticillata has been studied. The effect of NaCl in the concentration range of 5–10 g/L for 24 h leads to an increase in photosynthesis, pigment content, and lipid component rearrangement. A negative effect on membrane permeability and photosynthesis is observed under the action of NaCl at a concentration of 20 g/L. A decrease in the relative content of monogalactosyldiacylglycerol and an increase in digalactosyldiacylglycerol and sulfolipid are found in glycolipids. In the fraction of phospholipids, the relative content of phosphatidyl -choline, -ethanolamine, -inositol decreases and the contribution of phosphatidylglycerol increases with increasing NaCl concentration. Changes in the sterol component of membranes are associated with a decrease in the concentration of stigmasterol and increase in β-sitosterol. Adaptive rearrangements in the composition of pigments and membrane structure indicate a high functional activity of the photosynthetic apparatus of H. verticillata, which allows this species to achieve stability in saline ecotopes.

The removal of endocrine-disrupting xenobiotics, technical nonylphenol (NP) and 4-tert-octylphenol (OP), from aquatic environment by the cyanobacterium Planktothrix agardhii has been studied. It is shown that nonyl- and octylphenols are removed from aqueous medium in the presence of the cyanobacterium P. agardhii mainly via abiotic pathways—photolysis and hydrolysis—and biodegradation by cyanobacterial cells rather than by adsorption and accumulation in the cells. P. agardhii has a higher destructive and sorption ability for nonylphenol compared to octylphenol. The results indicate the possibility of self-purification of water bodies contaminated with alkylphenols with the participation of the mass species of cyanobacteria Planktothrix agardhii.

The effects of dietary zinc, copper or mercury (9.8, 9.5 and 0.66 mg/kg wet weight of forage, respectively) on different aspects of fish feeding behavior in common carp were evaluated. The latency to leave the starting chamber after its front wall was raised (t₁) and latency to feed (latent time of feeding, t₂) as well as the amount of food consumed or ration (the quantity of eaten chironomid larvae for 3 min of observation) were registered. By the end of the experiment under the impact of Hg, the t₁ value increased by 20% and t₂ value increased 5.6 times. The amount of food consumed decreased by 38%. The latency to leave the starting chamber under the impact of metal significantly increased during 20–30 days, followed by decline. The dynamics of the feeding reaction rate under the impact of metal differed: the maximum changes in t₂ value are noted under the impact of Cu: they were increased in the 2nd and 5th decade (3.7 and 6.1 times, respectively). The amount of food consumed in the presence of Zn either increased or remained at the control group level, but under the action of Cu and Hg was in most cases lower (by 37% at the most).

In the course of a laboratory experiment in microcosms, it is shown that the input of semiaquatic bird droppings promotes an increase in Copepoda abundance. The number of Copepoda decreases with increasing time of excreta drying in the air, but remains above the control values. The results of water biotesting from the microcosm using Ceriodaphnia dubia Richard demonstrate that the fecundity of the Cladocera increases with the increasing duration of excrement in the air. An assumption is made that the predominance of one or another group of Crustacea is determined by the rate of inflow of bird excrements and may indirectly depend on the ratio of nitrogen and phosphorus in water and, consequently, in feeding objects of crustaceans.