Vol 10, No 3 (2017)

We have discussed some aspects of the production and efficiency of energy use in aquatic ecosystems. Ecosystem production is defined as the difference between the gross total primary production and total expenditures for metabolic processes in all organisms of the ecosystem. We have obtained equations showing the dependence of ecosystem production on the average depth of a waterbody and the share of the primary production of phytoplankton in the total production. The mean value of the coefficient of ecosystem efficiency in some waterbodies (53%) indicates that aquatic ecosystems use energy efficiently. The efficiency of the energy use increases with an increase in the biomass turnover rate. High production in the ecosystem can be obtained if its structure is simpler.

The content of total free nucleotides (TFNs) in the plankton of the Rybinsk reservoir and in specific size fractions of the plankton has been determined by the spectrophotometric method modified by the authors. The content of TFNs amounts to 58.1 ± 5.4, 75.2 ± 4.6, and 64.1 ± 7.3 μg/L in spring, summer, and autumn, respectively, and exhibits a close correlation with the total plankton biomass (r = 0.67), whereas the TFN/Chl parameter is closely correlated to the ratio of autotroph and heterotroph organism biomass (r = 0.96). The contribution of the fraction of more than 3 μm in size (microplankton and nanoplankton) to the TFN pool is 77 ± 4% in spring, 74 ± 3% in summer, and 47 ± 3% in autumn, whereas the contribution of the fraction of 0.45–3 μm in size (ultraplankton) during these seasons is 23 ± 4, 26 ± 3, and 53 ± 3%, respectively. Regression equations that can be used to infer an estimate of plankton biomass from TFN content have been proposed.

Fifty species of free-living nematodes have been found in the Yên River estuary (northern Vietnam), ten of which are newly described species. The dominant species are Valvaelaimoides macroamphida Gagarin, 2016; V. minor Gagarin, 2016; Micromicron cephalatum Cobb, 1920; and Sphaerotheristus nothus Gagarin, Nguyen Vu Thanh, 2008. A list of the nematodes species, an illustrated description of the new species Theristus consobrinus sp. n., the main morphometric parameters of 13 valid species of the species group flevensis of the genus Theristus, and a pictorial key for determining males of this species group are provided.

The specific flora of temporary plant groupings in the lake coastal areas during the periodic shallowing has been investigated. The structure of ecological groups in respect to humidification, life forms, and phytocoenotic groups has been analyzed as the aggregate of various plant-life strategies under dramatic changes in the environment. The spatial distribution of the species and long-term dynamics of the floristic complex have been found to be dependent on the soil type.

Macrozoobenthic communities are described and classified on the original data (166 stations) for the small rivers and streams of the mountains of Bulgaria (Balkan and Rhodope mountains) and European Turkey (Istranca range). Seventeen types of communities are described—their habitats, the total abundance of macrozoobenthos, gradation saprobity and complexes of the dominant species. A brief taxonomic review of the macrozoobenthos of the region is provided. Reasons for the variability of rheophilic macrozoobenthos communities and regional characteristics of the communities associated with the local landscape and fauna are discussed.

The results of a study on the parameters of reproductive capacity in roach from the Sheksna and the Volga reaches of the Rybinsk Reservoir are presented. The Volga reach is relatively clean, while the Sheksna reach is subject to the strongest anthropogenic load. In 2011, the average values of the absolute and relative fecundity, as well as the egg size, in roach Rutilus rutilus (L.) from the Volga reach were higher than those in roach from the Sheksna reach, but differences are mainly statistically insignificant. The data of the study indicate the adaptation of the investigated roach to the negative influence of the Sheksna reach contamination and, in particular, its preservation of a sufficient level of reproductive capacity.

Antimicrobial properties of the blood serum and the content of immune complexes, lipid peroxidation products, and antioxidants in the blood serum and liver have been analyzed in roach living in areas of the Kuban River with different levels of anthropogenic pollution. The relationship between the studied parameters and fish habitats is shown.

The effect of nickel chloride concentrations in the range of 1–1000 mg/L on seed germination and the development of organs and pigment system in seedlings of the helophyte common water-plantain Alisma plantago-aquatica L. and hygrohelophyte greater water-parsnip Sium latifolium L. has been studied. It is shown that nickel chloride has practically no effect on the germination of the common water-plantain; however, it suppresses the germination of the greater water-parsnip. It is demonstrated that the toxicant suppresses the growth of seedlings and synthesis of photosynthetic pigments. The length of cotyledons and hypocotyl is less variable, with a much stronger effect on roots and leaves. It is determined that the morphometric parameters are less sensitive to the toxicant when compared to physiological ones. In general, the common water-plantain is more resistant to the effect of nickel chloride than the greater water-parsnip.

The currently applied recommendations for the number of samples for benthic macroinvertebrate investigations are unclear and contradictory. Therefore, we have attempted to determine the optimal number of samples applicable for an unbiased estimate of the current status of macrozoobenthos, which makes it possible to determine the significance of the obtained values at the same time.

Oligochaete Quistadrilus multisetosus (Smith, 1900) has been recorded in the Rybinsk Reservoir for the first time in this region. The abundance and spatial distribution of the species population in autumn 2013 are presented.