Vitaliy P. Semenchenko

Recently, a spread of naturalized alien species of invertebrates throughout the water bodies of Belarus is observed, but new species are also appearing. For the first time the freshwater jellyfish was revealed using environmental DNA, and then local residents observed the bloom in the summer, when mass accumulations of invertebrates lived in the water column of various water bodies. Taking into account the life cycle of jellyfish and their ability to live in the form of polyps, it is expected that this species will be found in other places because of increase in water temperatures of water bodies and streams.

The problem of biological invasions is currently one of the most significant and well-recognized ones in light of influence on biodiversity across all ecosystems. To examine which new species may be introduced and established in the aquatic ecosystems of Belarus in the near future (5–10 years), an evaluation of the ranges, the vectors of invasion, and the biology of potential invaders was made. Of the 89 potentially nonnative species, only 32 were included in the list of the most probable alien species which are most likely to inhabit Belarusian waters in the near future. In addition, seven species with high capacity for invasion were singled out from the list of the potential alien species.

Rank distribution of macrozoobenthos abundance on the different sites of the Neman River basin was analyzed. The number of species correlated with the total abundance of macrozoobenthos. The type distribution of species corresponded to the lognormal distribution. The evenness coefficients in communities averaged 0.7. The low coefficient of the relationship between evenness and total abundance of macrozoobenthos species (r = 0.28, р > 0.05) indicated a slight overlap of ecological niches in the macrozoobenthos communities. This was due to wide range of functional trophic groups that leads to reduce competition between species.

Связь структуры макрозообентоса с гидрохимическими показателями в реках разного порядка бассейна Немана Связь структуры макрозообентоса с гидрохимическими показателями в реках разного порядка бассейна Немана

The relationships between the hydrochemical and structural characteristics of the macrozoobenthos community, including biotic indices is analyzed in the rivers of the Neman basin in the spring and summer periods. The list of hydrochemical characteristics included pH, dissolved oxygen concentration, the concentration of ions of ammonium and nitrate nitrogen, dissolved phosphorus, and heavy metals. A close correlation was found to exist between the structural characteristics of zoobenthos and water hydrochemical composition; it can be clearly seen in the summer period. The maximal values of the correlation coefficients were obtained for the relationship between the shares of EPT and oligosaprobic species in the total number of macrozoobenthos. The correlation between the number of macrozoobenthos species and the hydrochemical characteristics was found to be unreliable. The importance of the multimetric approach, taking into account both the hydrobiological and hydrochemical characteristics was emphasized.

Comparative analysis of invasive aquatic animal impact was performed on the basis of GISS (Generic Impact Scoring System). Species ranking according to their resultant ecologic and economic effect showed the maximum values for F. limosus and C. gibelio. Dreissena polymorpha was also characterized by a high invasive threat, while the score estimates for invasive fish species were relatively low. The analysis of the confidence level in expert conclusions for the tested species was carried out, and the species for which the results obtained were significantly different among experts were indicated.

Установлено, что наиболее важным источником пищи, который определяет динамику рождаемости и, соответственно, популяционных показателей у Daphnia cucullata и Bosmina logirostris является размерная фракция фитопланктона, находящаяся в пределах от 5 до 20 мкм. Оценка трофических условий по общей биомассе фитопланктона или сестона не отражает пищевую обеспеченность кладоцерного зоопланктона и их воздействие на динамику численности популяций.

The spread rates of alien species of Amphipoda and Mysida were calculated for the Dnieper, Pripyat, and Neman rivers within the territory of Belarus. The maximum values of spread rate were obtained for Dikerogammarus villosus (in the Pripyat River, 37.8 km/year; in the Dnieper River, 17 km/year) and Dikerogammarus haemobaphes (in the Pripyat River, 53.6 km/year; in the Dnieper River, 17 km/year), while the minimum values of spread rate were calculated for mysids Paramysis lacustris (in the Dnieper River, 0.4 km/year) and Limnomysis benedeni (in the Dnieper River, 0.6 km/year) and also for amphipods Chelicorophium robustum (in the Dnieper River, 0.5 km/year) and Echinogammarus trichiatus (in the Dnieper River, 1.3 km/year). The differences in the spread rates of the species are related to the time of their first record at the monitoring sites and the intensity of shipping in the studied rivers.

This article presents the results of a study of the species and trophic structure of the macrozoobenthos community in the littoral zone of mesotrophic Lake Obsterno (Republic of Belarus) having different macrophyte beds (Chara, reeds, and lily). The results of ANOVA have shown the influence of studied biotopes on the number of species and Shannon index. The number of species increased from summer to autumn, but the Shannon index was minimal in the middle of summer. Significant differences in species abundance between biotopes have been obtained for oligochaetes, chironomids, active filter feeders, and predators. There are no differences for Ephemeroptera and Trichoptera. The mean values of species similarity for the studied period are 68.9, 74.1, and 70.0% for reeds, lily, and Chara, respectively. The trophic similarity between groups were 66.3, 54.1, and 69.7%. Significant differences between species and trophic similarity are noted only for the lily beds. The values of variability of species structure during the period are higher than trophic structure; i.e., trophic structure is more stable when compared with species structure.