Biodiversity of Fishes of River Ecosystems of the Western Tyan-Shan

The paper cites data on the biological diversity of fishes in the river ecosystems of the Western Tien Shan. Data on the diversity and distribution of species are presented and analyzed. The role of various factors affecting the variability of species numbers and their range is discussed, which is important for development of a number of measures on conservation of rare and vanishing fish species.

Organic Matter Decomposition in River Ecosystems: the Role of Microbial Interactions Regulated by Environmental Factors

Microbes are the critical contributors to the organic matter decomposition (OMD) in river ecosystems. However, the role of microbial interactions on the OMD in river ecosystems and the regulation of environmental factors to the microbial interactions were not considered previously thus tacked in this study. Cotton strip (CS) as a substitute for organic matter was introduced to Luanhe River Basin in China. The results indicated that CS selectively enriched bacterial and fungal groups related to cellulose decomposition, leading to the cotton strip decomposition (CSD). In these groups, bacterial phyla Proteobacteria, fungal phyla Rozellomycota and Ascomycota were the dominant groups associated with the CSD. Bacteria and fungi on CS cooperatively formed a co-occurrence network to achieve the CSD. In the network, the key modules 2 and 4, mainly composed of phyla Proteobacteria and Ascomycota, directly promoted the CSD. Keystone taxa maintained the stability of microbial network structure and function, and regulated microbial groups associated with CSD in the key modules, rather than directly decomposing the CS. Notably, this study profoundly revealed that water temperature and total nitrogen (TN) regulated the keystone taxa and key modules in microbial interactions and then promoted the OMD. The two key modules 2 and 4 were significantly correlated with water temperature and TN in water, and two keystone taxa (bacterial genera Emticicia and Flavihumibacter) were significantly associated with TN. The research findings help us to understand the microbial mechanism of the OMD in rivers, which provides valuable insights into improving effective management strategies for river ecosystems.

Water Quality Analysis in a Subtropical River with an Adapted Biomonitoring Working Party (BMWP) Index

Subtropical rivers in developing countries often lack adequate monitoring, which makes it difficult to comprehensively determine their water quality when faced with different anthropic impacts. There are no proper protocols in the regulations to incorporate indicators and adapt them to different biogeographic regions, limiting the potential success of conservation and restoration of river ecosystems. This study proposes implementing macroinvertebrates as bioindicators of water quality in river ecosystems, and modifying the calibration of the widely used Biomonitoring Working Party (BMWP) index for its adaptation in a subtropical river. The Duero River, Mexico, was used as an example in this study. Data were explored with multivariate statistics, and the water quality and habitat values were averaged to obtain the families’ bioindication values and the index categories. The BMWP adequately described a deterioration gradient from the origin to the river mouth (from fair to extremely polluted), with some intermediate recovery points related to the presence of springs. Its performance was compared with other biological indices and exhibited a positive relationship with all of them. In addition, how BMWP changed over time was analyzed by examining previous samples, and highlighted increased river deterioration over time. A calibrated BMWP will allow for long-term monitoring at a low cost.

RIVER ECOSYSTEMS OF UKRAINE: NATURAL FEATURES, PROBLEMS OF TRANSFORMATION AND RECOVERY MEASURES

The current state of ecosystems of rivers of Ukraine - their natural features and consequences of powerful anthropogenic activity are analyzed. The problem of coastal areas of rivers and reservoirs is considered. Methods of rehabilitation of the cascade of Dnieper reservoirs and their coastal territories are determined. Extensive farming with the destruction of coastal lands up to 80-90% is one of the main factors in the ecological crisis of river ecosystems. The floodplains of most small rivers of Polissya are developed for agricultural lands by almost 50-60%, Forest-steppe and Steppe - by 70-90%. Nevertheless, the efficiency of agricultural land use in Ukraine is lower than in Europe and developed countries. Agricultural fields are located on the slopes and floodplains of rivers, so the erosion of coastal areas has reached unprecedented proportions. The creation of the Dnieper reservoirs has created a number of environmental problems, led to a sharp change in the basis of local erosion. One third of their total length is actively destroyed by wind waves and denudation processes, runoff and other types of currents. The area of land lost as a result of the destruction of the shores is already about 6.5 thousand hectares. The destruction of the cascade shores annually leads to the loss of a significant amount of coastal land, affects the use of the shores and adjacent areas, causes emergencies, accidents and catastrophes, especially in settlements where the negative impact of natural factors is exacerbated by man-made factors. The condition of the coastal area directly affects the condition of the water area. Urban planning of coastal areas should help preserve and maintain the natural balance of the river ecological system - the establishment of restrictive "green lines" and water protection zones, shore protection, creation of recreation areas and their improvement, paving tourist routes, restricting protected areas and more. These urban planning measures should take into account the zonal features of rivers and take into account the uniqueness of each river ecosystem in Ukraine.

River Ice Can Shape Watershed Ecology

As river ice cover decreases, the physical and biological changes to river ecosystems vary with the watershed characteristics and river size.

THE FINDING OF THE INVASIVE AMPHIPOD GMELINOIDES FASCIATUS (STEBBING, 1899) IN WATERCOURSES OF THE ONEGA LAKE BASIN

The invasive amphipod Gmelinoides fasciatus (Stebbing, 1899) was not previously recorded in the rivers of the Onega Lake basin, although it has spread widely in its littoral in recent years. In 2019 and 2020, this species was found to inhabit the estuarine zones of watercourses (the Rybreka River and the Drugaya River) at a considerable distance from the lacustrine littoral zone (0.5 and 1.7 km, respectively). It was revealed that G. fasciatus is included in the communities of both pools and riffles, and in some areas reaches dominant positions in the macrozoobenthos, which indicates the possibility of further expansion of its range due to the river ecosystems of the region.

N2O emission and its influencing factors in subtropical streams, China

Background Rivers and streams are one of the primary sources of nitrous oxide (N2O) which is an important greenhouse gas with great global warming potential. Yet, over the past century, human activities have dramatically increased reactive nitrogen loadings into and consequently led to increased N2O emission from the river ecosystems. Here, we carried out a study in two subtropical rivers, i.e., Jinshui River and Qi River with slight and intense human disturbance in their respective catchments in China. The study intended to explore spatial variability and seasonality in N2O emissions, and the relative importance of physicochemical variables, nitrification and denitrification potentials, and functional genes abundance influencing N2O emissions. Results N2O concentration, N2O saturation, and N2O flux of Jinshui River peaked in high flow season. N2O concentration, N2O saturations, and N2O flux in Qi River and downstream of Jinshui River were significantly higher than that in other areas in normal and low flow seasons. N2O concentration was positively correlated with water temperature, water NO3−, and DOC, negatively correlated with water NH4+ and DOC/NO3− (the ratio of dissolved organic carbon to NO3− in water), and positively correlated with potential nitrification rate in high flow season, but not correlated with functional genes abundance. Both rivers had lower N2O saturation and flux than many freshwater systems, and their EFr-5 (N2O emission factor for river) was lower than the recommended values of IPCC. Conclusions While the two rivers were moderate sources of N2O and N2O emissions in river systems were normally elevated in the summer, areas with intense human disturbance had higher N2O concentration, N2O saturations, and N2O flux than those with slight human disturbance. Physicochemical variables were good indicators of N2O emissions in the river ecosystems.