The impact of the placer gold mining in Eastern Transbaikalia (Russia) on the environment components of river valleys in the Amur River basin

Based on the results of the analysis of satellite images and field observations, data on the length of the gold-bearing placers disturbed by the development along a number of main tributaries of the Shilka and Argun rivers are presented, the formed technogenic relief forms are indicated. Depending on the method of development, two types of technogenic landscapes have been identified - the excavation-dump with hydromonitor mining and belt trench-dump when washing with drags. The main directions of research on the assessment of placer gold mining in the natural complexes of river valleys are proposed.

Quantifying the Impact of Future Climate Change on Runoff in the Amur River Basin Using a Distributed Hydrological Model and CMIP6 GCM Projections

The Amur River is one of the top ten longest rivers in the world, and its hydrological response to future climate change has been rarely investigated. In this study, the outputs of four GCMs in the Coupled Model Intercomparison Project Phase 6 (CMIP6) were corrected and downscaled to drive a distributed hydrological model. Then, the spatial variations of runoff changes under the future climate conditions in the Amur River Basin were quantified. The results suggest that runoffs will tend to increase in the future period (2021–2070) compared with the baseline period (1961–2010), particularly in August and September. Differences were also found among different GCMs and scenarios. The ensemble mean of the GCMs suggests that the basin-averaged annual precipitation will increase by 14.6% and 15.2% under the SSP2-4.5 and SSP5-8.5 scenarios, respectively. The increase in the annual runoff under the SSP2-4.5 scenario (22.5%) is projected to be larger than that under the SSP5-8.5 scenario (19.2%) at the lower reach of the main channel. Future climate changes also tend to enhance the flood peak and flood volume. The findings of this study bring new understandings of the hydrological response to future climate changes and are helpful for water resource management in Eurasia.

Impact assessment of solid runoff on heavy metals migration during high floods on the Amur river

Inhomogeneity of the concentrations of chemical elements in the cross-section of the Amur River is considered as a function of the state of their soluble and suspended forms. Flooding of wetlands and urbanized areas contributes to the removal of pollutants into the river channel. The wide spread of fens on the left bank contributes to the concentration of organic matter along the left bank of the river. Terrigenous material mostly comes from the right bank, where agricultural fields are concentrated. The ratio of their concentrations is maintained by the duration of the flood. The mechanisms of redistribution of elements between their suspended and soluble forms have been studied. The mechanisms of sorption of chemical compounds on mineral and organic colloids are described. It was found that mineral colloids with a negative charge due to electrostatic attraction sorb electrically neutral compounds (hydroxoaqua complexes [Mn(OH)2(OH2]0, ammonia [Cu(NH3)4(OH)2]0. The role of organic material in the redistribution of chemical compounds between soluble and suspended forms is shown. Organic colloids with molecular mass > 5.0 kDa precipitate complex cations – [FeHSO4]+, [FeHSO4]2+, [CuHSO4]+. An organic substance with a molecular mass of <2.0 kDa has a greater complexing ability for Fe(2)3+, Cu2+, Zn2+, Mn2+ ions. They bind metals to organo-mineral complexes by chemical interaction and form mobile organo-mineral complexes and heteropolar salts.

Biodiversity of a small water body during the initial filling phase (the Amazar River of the Amur River Basin, Russia)

In 2017, for the purposes of the Pulp and Saw Mill (PSM) “Polyarnaya”, the spillover dam was constructed on the Amazar River, a left tributary of the Amur River. Upon completion of the dam construction, the waters of the river formed a small river reservoir PSM “Polyarnaya”. This work covers findings on components and quantities of the newly formed reservoir at its initial stage and the data on biodiversity of its feeding flows. At this stage, the species composition of the flora and fauna in the reservoir falls in between the lacustrine and the riverine ones. The riverine conditions are observed in the upstream area of the reservoir; the middle area bears an intermediate status; while the limnetic zone near the dam features transformation of the river system into a lake-like running-water ecosystem. Seasonally, in the period from spring to autumn, phytoplankton showed a decreasing trend of the quantitative values; whereas the total abundance and biomass of zooplankton were increasing; zoobenthos featured lack of trends; macrophytes contents were different from season to season being abundant in the Amazar River near the urban settlement in spring and in the Amazar River downstream from the dam in autumn. Consequently, the initial stage of the formation of the reservoir is rather similar to original watercourses in the physical and chemical parameters and in the composition of flora and fauna as well.

Mineralization and salt composition of the waters of the Middle Amur

The spatial and temporal variability of water salinity and salt composition of the Amur River near Khabarovsk in 2017-2021 was considered. An uneven distribution of water salinity over the river width was established, the greatest differences were observed in the winter low-water period, the lowest in the period of spring floods and floods. The maximum value of salinity was noted in winter, in the period of open channel – after very strong floods.

Bioindication of mercury pollution of the Amur River during the ice-covered period

The results of the layer-by-layer research of a river ice cores by using spectral and microbiological methods were presented. The impact of the mercury on sulfate-reducing bacteria activity from different layers of ice that had been sampled in March 2016 in the lower Amur River in Khabarovsk city was found. It was found that mercury concentration range of 0.0005-0.001 mg/l stimulated the sulfate-reducing bacteria activity, which were into the ice throughout the study area of the Amur River. To a large extent, this effect was typical for the ice that was sampled in the right bank of the Amur River near Khabarovsk city, where mercury pollution of the aquatic environment had been detected repeatedly. The activity of biogeochemical processes into the ice determined by high concentrations of organic substances, by the pollution of the aquatic environment with mercury during the ice cover formation, and by the abundance of cultivated heterotrophic and sulfate-reducing bacteria. During the ice drift and ice melting, the secondary pollution with toxic substances of various genesis of the aquatic environment occurs, which can have a negative impact on a hydrobionts.

Biological Invasion of Fish Parasite Neoergasilus japonicus (Harada, 1930) (Copepoda: Ergasilidae) in Lake Grand Laoucien, France: A Field Study on Life Cycle Parameters and Reasons for Unusual High Population Density

The fish parasite, Neoergasilus japonicus (Harada, 1930), native to Eastern Siberia and the Amur River catchment area, invaded European water bodies in the middle of the last century, possibly due to the human-mediated distribution of fish in the Amur complex (i.e., the genera Hypophthalmichthys and Ctenopharyngodon). In the deep karst lake, Grand Laoucien (Marseille area, France), this species had an unusually high population density (from 1000 ind./ m3 in zooplankton to 4000 ind./ m3 in the nearshore area) during the free-living period of its life cycle. The annual cycle of N. japonicus includes a 5-month overwintering of fertilized females attached to fish fins and, following this, a five- to six-generation chain from March to November, when the free-living stages in the population alternate with parasite females which attach to their hosts for breeding. The population density of the parasites in zooplankton increased exponentially from spring to autumn, which positively correlated with temperature. We found a strong correlation between N. japonicus density and the community development of microphytobenthos, but not between N. japonicus and phyto- or zooplankton dynamics. The local contributing factors included a seasonal three-fold decrease in water levels and the development of anoxia in profundal waters, which led to a high ambient fish density and thus susceptibility to the parasite. Although the free-living parasite represented only 1% of zooplankton production, it consumed up to 25% of small invertebrate productivity. The maximum intensity of infection reached 140 parasites per fish, or 4.14 per g of weight. The high infection of fish with this parasite, in our opinion, indicated the danger it poses to the local ichthyofauna, which first encountered this new parasite.

Characteristic of phytoplankton and water quality assessment in the Amur River at Khabarovsk in the ice-free period of 2018–2019

Species composition and taxonomic structure of phytoplankton communities in the main channel of the Amur at Khabarovsk (Russia) were monitored from spring to autumn of 2018–2019. In total, 187 species, varieties and forms of algae and cyanobacteria were found belonged to 8 phyla (Cyanobacteria, Bacillariophyta, Charophyta, Chlorophyta, Heterokontophyta, Rhodophyta, Euglenozoa, and Miozoa) and 75 genera. Diatoms formed the basis of the algal flora (94.7 % of the total species number). Mass vegetations of the diatoms and charophytes were observed with dominance of Asterionella formosa, Aulacoseira islandica, A. ambigua, A. granulata var. granulata, A. granulata var. angustissima, Ulnaria ulna, Diatoma tenue, Nitzschia acicularis, Stephanodiscus sp., Tabellaria flocculosa, Hannaea arcus var. rectus, Melosira varians, Fragilaria capucina var. vaucheriae, F. crotonensis, and Mougeotia sp. ster. Total number and biomass of plankton algae and cyanobacteria varied in the ranges of 1.74–5724.39 million cells/L and 2.5–2648.5 mg/L in spring-summer and 0.07–0.62 million cells/L and 0.2–1.4 mg/L in autumn. The water quality was evaluated by Pantle-Buck method modified by Sládeček as the betamezosaprobic III class (slightly polluted).

Range dynamics of some nemoral species of Lepidoptera in the Russian Far East due to climate change

New finds of seven East Asian Lepidoptera species in the Russian part of the southern Priamurye (Amur Basin area) are presented. Lobocla bifasciata (Bremer et Grey, 1853) (Hesperiidae), Acosmeryx naga (Moore, [1858]) and Rhagastis mongoliana (Butler, [1876]) (Sphingidae) were found in the Amur Oblast’ for the first time. Ambulyx tobii (Inoue, 1976) (Sphingidae) was first discovered in the Khabarovsk Kray; it was also found in the Chernigovsky district of the Primorsky Kray, northward from the previously known localities. New finds of very rare nemoral species, Chrysozephyrus brillantinus (Staudinger, 1887) (Lycaenidae) and Clanis undulosa Moore, 1879 (Sphingidae), in the Khabarovsk Kray are reported. It is shown that the subtropical and tropical species Siglophora sanguinolenta (Moore, 1888) (Nolidae), first collected in Russia in 2020, has successfully naturalized in the southern Khabarovsk Kray. New finds of these species indicate that the species have extended their ranges northward and naturalized in new areas. This has occurred due to climate changes in the Amur River basin over the past decades such as the rising average annual and average air temperatures during cold periods.