Benthic fauna state research in the zone of diamonds placer deposit development in the basin of the lower reaches of the Lena river

The global equilibrium in all natural ecosystems, including in the aquatic environment, has been disturbed in the conditions of intensive technogenic impact on the easily attenuated environment of The North. In the valley of the river Molodo, in the basin of the lower reaches of the River Lena, the industrial development of placer application of diamonds is underway. To assess the impact of the development of mineral deposits on the hydrobiological state of rivers, it is necessary to carry out biological monitoring, for which benthos is widely used. In connection with this, a study of the modern quantitative and qualitative state of the benthic fauna of the River Molodo is conducted. An assessment of changes in invertebrate communities both in the background section of the river and in areas prone to anthropogenic impact was made. Sampling of benthos was conducted in the field. Species composition, structure, biomass and abundance of benthic fauna was determinated in the laboratory. A faunistic list of the bottom fauna of the river is compiled, which includes 41 species, belonging to 6 systematic groups. Among them, the largest species diversity was noted in the group of larvae of chironomids - 18 species and forms, and larvae of young scions of 7 species and forms. As a result of studying the qualitative composition and quantitative development of hydrobionts, waterways with various information of communities have been identified. The highest diversity of aquatic invertebrates at the background station. Due to the deterioration of water quality associated with mining operations downstream, there is a decrease in the species diversity of the bottom community. Analysis of the materials shows that a change in the species composition causes a rearrangement of the trophic bonds of benthic organisms. Thus it’s defined that in the area of mining and downstream there is a change in the quality composition, quantitative development and structure of bottom biocenoses, compared with the background area. Species diversity is reduced, and individual trophic groups in the mining area fall out of the ecological system.