Comparison of Toxicity of Sediments from Rivers with Different Levels of Anthropogenic Load (Middle Volga Region, Russia) Based on Elutriate and Whole Sediment Tests

Description of chemical characteristics and toxicity testing of whole sediment and elutri-ate have been performed with 35 samples taken during the monitoring of rivers in the Middle Volga region (Tatarstan, Russia) in 2013. The locations analyzed are sites associated with agriculture, forestry, and petroleum hydrocarbons (oil) production. The toxicity tests include: (1) Chlorella vulgaris (algal) elutriate test, (2) Paramecium caudatum (ciliate) elutriate test, (3) Daphnia magna (cladoceran) whole sediment toxicity test, and (4) Heterocypris incongruens (ostracod) whole sediment toxicity test. The concentrations of metals in 43% of sediment samples have been found to exceed probable effect concentration sediment quality guidelines (SQGs). However, the concentrations of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides have turned out to be below SQGs in most sites. The correlation analysis has shown metal toxicity to daphnid reproduction and ostracod growth (R2 = 0.34–0.64) and ammonia (R2 = 0.49–0.54). A higher percentage of samples have shown toxicity in the whole sediment tests (86%) compared to the elutriate tests (54%). A total of 91% of samples have demonstrated toxicity for at least one species. Toxicity has been most frequently observed for daphnid reproduction (83% of samples) and ostracod growth (56% of samples) compared to daphnid (23%) survival, ostracod (11%) survival, and ciliate reproduction (54%) or algal growth (54%). The most polluted sediments have been registered in the area of oil production. The comparison of toxicity of the samples from different types of areas has indicated that 100% of samples from the oil production area, 94% of samples from the agricultural area, and 50% of samples from the forest area were toxic to at least one test organism

The impact of herbivorous fish introduction on the formation of fish communities in water bodies (based on the Khauzkhan Reservoir, Turkmenistan)

The dynamics of the structure of fish species complex in the community of the Khauzkhan Reservoir (Turkmenistan) has been analyzed from the time when it was filled in 1966 to 1990. In order to quantify the observed changes in the fish population, the indices of diversity and dominance and the dynamic phase portrait method have been used and the structural changes have been visualized. Changes in the dominant complex of species and the dynamics of the relative abundance in the catches of fish groups belonging to different faunal complexes and ecological groups have been also considered. A relation between the changes in the structure of fish species complex in the community under study and the changes in the ecosystem of the reservoir has been found. It has been shown that the introduction of herbivorous fish from the first years of the reservoir filling has resulted in a new stage in the formation of its ichthyofauna, which is known as the stage of acclimatization, and in the extension of the formation process. Currently, the fish population of the Khauzkhan Reservoir is at the 4th stage of formation – the stage of an increase in the anthropogenic impact

The population status of pikeperch, Sander lucioperca (Linnaeus, 1758), in the Kuibyshev Reservoir (2000–2018)

The population status of pikeperch, Sander lucioperca (Linnaeus, 1758), in the Kuibyshev Reservoir was studied for the period from 2000 to 2018. The species is the dominant predator here. The monitoring was based on data on the dynamics of the population size and generations, as well as changes in the age structure, growth rate, and mortality. The obtained results reveal that the pikeperch population oscillated around an equilibrium state in 2000–2007. During this period, its size varied insignificantly. Subsequently, the abundance of specimens increased, and the population became even more balanced, which has been observed up to date. The index of population wellbeing in the equilibrium states has remained unchanged throughout the two decades. However, some negative tendencies have taken place over the past 10 years: an increase in the fishing pressure and a reduction in the number of older specimens in the catches. The approach used in this study should be helpful for assessing the status of fish populations, promoting sustainable fish stock exploitation under the conditions of unstable hydrological regime of reservoirs and weak control over fishing in the conservation of fish resources

Conference dedicated to the 100th anniversary of the birth of Alexey Konstantinovich Skvortsov

The brief information on the eight conferences (2012-2019) in the memory of A.K. Skvortsov is given in the article. A review of scientific reports and events held at the 9th Anniversary Conference is made