Water quality and zooplankton community of the Eme River, Umuahia, Southeast Nigeria

Aquatic ecosystems and biota are often adversely affected by anthropogenic activities. Consequently, zooplanktons have been used to monitor anthropogenic impacts because of their sensitivity to their environment. Water quality and zooplankton community of the Eme River, Umuahia, was assessed between December 2017 and November 2018. The study was carried out in six stations in relation to human activities. Human activities in the watershed were dominated by sand mining. A quantitative filtration method was used for the zooplankton sample collection while standard sample collection and analytical methods were used for the water samples. The zooplankton species recorded were 27 while the most abundant zooplankton group was Rotifera. A known pollution indicator, Daphnia pulex, had the highest number of individuals. The effects of human activities in the watershed were reflected in the results of some of the physicochemical parameters of the river. The zooplankton assemblage and community structure also reflected the effects of human activities in the river. Combined effects of human activities and season contributed to the relatively low zooplankton abundance recorded particularly in some downstream stations. The impacts of sand mining on water quality and zooplankton were more remarkable in the downstream stations (4 6) where the activity was intense while a large number of children swimming and related activities during the dry season had some impacts in station 1. The dominance of indicator and tolerant species indicated that the river was undergoing eutrophication. Sand mining among other observed anthropogenic activities was a major contributor to the nutrient enrichment in the river. The major water quality parameters influencing the zooplankton community structure was revealed by canonical correspondence analysis.

Influence of breeding strategy on genetic diversity of individuals

Using a computer simulation model, we tried to investigate how the transition from sexual reproduction to asexual reproduction will affect the population of diploid organisms with a neutral character of molecular evolution. At the same time, special attention was paid to the specificity of microsatellite markers. In this paper, we develop fast and inexpensive methods for assessing the changes in populations that occur with a change in reproductive strategy.

Actual inflow of riverine sediment load into Lake Baikal: main tributaries the Selenga, Upper Angara, and Barguzin Rivers (Russia)

The sediment load delivery into Lake Baikal from its main tributaries the Selenga, Upper Angara, and Barguzin Rivers has been reduced since the mid-1970s. This is explained by climate change and socioeconomic activities. Integrated analysis of changes in hydro-meteorological parameters (water discharge, sediment load, air temperature, precipitation) and their trends over the period 1946 1975 (baseline) and 1976 2017 (warming) is performed. Changes in natural processes and human activity were negligible during the baseline period. During the warming period, the greatest reduction of the sediment load inflow against the background of temperature rise and precipitation decrease occurred in the interval between 1996 and 2017 in the Selenga River, between 1985 and 2017 in the Upper Angara River, and between 1992 and 2017 in the Barguzin River. The flux of the sediment load into these rivers was 768 103, 88 103, and 29 103 t y 1, respectively. This is 2 3 times less than the average multiyear values for all period of 1946 2017, which are usually used when characterizing sediment load runoff from these rivers. Currently the values in the given intervals correspond to the actual sediment load flux into Lake Baikal from the main tributaries.

Optical characteristics of water at the mouth of the Ob River

As a result of the field studies (August 25 September 1, 2020), new data were obtained on the optical characteristics of water at the Ob River mouth near the Salemal village (Yamal region, Yamal-Nenets Autonomous Okrug) during the lowest water level and the maximum development of hydrobiocenoses. We calculated the light attenuation coefficient ( ) in the spectral range from 400 to 800 nm, which varied from 1.5 to 21.5 m 1 during the study period, and the light absorption by yellow substance ys( ) from 0.1 to 12.2 m 1. Concentrations of yellow substance Cys and chlorophyll Chl were determined. For instance, chlorophyll concentrations in water samples taken at different stations of the Ob River ranged from 12.5 to 22.7 mg m 3. The maximum content of chlorophyll in our case was recorded at a depth of 14 m (station 5.3), which was 22.7 mg m 3. The yellow substance concentration determined optically by the calculated yellow substance light absorption coefficient at wavelength =450 nm ranged within 18.8 and 26.9 g m 3 with an average value of 22.1 g m 3. The average value of ys( ) at =450 nm over the study period was 4.7 m 1.

Identification of Baikal phytoplankton inferred from computer vision methods and machine learning

This study discusses the problem of phytoplankton classification using computer vision methods and convolutional neural networks. We created a system for automatic object recognition consisting of two parts: analysis and primary processing of phytoplankton images and development of the neural network based on the obtained information about the images. We developed software that can detect particular objects in images from a light microscope. We trained a convolutional neural network in transfer learning and determined optimal parameters of this neural network and the optimal size of using dataset. To increase accuracy for these groups of classes, we created three neural networks with the same structure. The obtained accuracy in the classification of Baikal phytoplankton by these neural networks was up to 80%.

PCR-screening of bacterial strains isolated from the microbiome of the Lubomirskia baicalensis sponge for the presence of secondary metabolite synthesis genes

The microbial communities of sponges (Porifera) are often a source of natural bioactive metabolites. From the microbiome of the endemic Lubomirskia baicalensis sponge, 35 bacterial strains were isolated and identified using molecular methods. The strains belonged to the phyla Actinobacteria, Firmicutes, and Proteobacteria (classes Alpha- and Betapriteobacteria). To analyze the strains for the presence of genes in the synthesis of secondary metabolites, polyketide synthases (PKS), PCR screening was applied using degenerate primers. Overall, 15 out of 35 strains contained PCR products corresponding in size to a fragment of the ketosynthase domain of the PKS gene cluster. Thus, the proposed method is applicable for rapid screening of the potential ability of microorganisms of different taxonomic groups to produce secondary metabolites. The work contributes to the study of the taxonomic diversity of cultured microorganisms, potential producers of biologically active substances, isolated from the microbiomes of Baikal sponges.

The geochronology of a palaeolake at the Pleistocene/Holocene transition in the Muya-Kuanda Basin (Eastern Siberia, Russia)

This article presents new data on the study of preserved wood from flooded forests in the Muya-Kuanda Basin, Eastern Siberia. On the basis of the stratigraphic position of a buried tree stump horizon, the analysis of the associated alluvial deposits and a new programme of radiocarbon dating, the chronology of formation and collapse for a Late Pleistocene pal eolake in the Muya-Kuanda Basin can be precisely determined. The accuracy of dating of geological events with the radiocarbon method and the possibility of linking them to calendrical dates is discussed. As a result of this research it is possible to connect the geochronology of the lake with archaeological sites in the Vitim Basin, both upstream and downstream along the river. The reasons for the periodic formation of substantial bodies of water in the Muya-Kuanda Basin are also discussed, with implications for decision making with regard to the modern economic development of the region.

Length-weight relationship and condition factor of endemic genus Seminemacheilus (Teloestei=Nemacheilidae) for Turkey

This study was aimed to determine the length-weight relationships and Fulton s condition factors of the genus Seminemacheilus that is endemic for Turkey. The specimens were collected from 2017 to 2019 using an electrofishing device (SAMUS 1000MP). The total length and the total weight of the examined specimens ranged from 3.5 to 9.1 cm and from 0.31 to 7.52 g, respectively. Based on the results, the growth coefficient values b ranged from 2.56 (S. ispartensis) to 3.48 (S. attalicus). Also, the condition factor of the studied fishesranged from 0.77 (S. dursunavsari) to 1.11 (S. attalicus). This study represents the first reports of length-weight relationship data for S. ahmeti, S. attalicus, S. dursunav ari, S. ekmekciae, and S. ispartensis from Turkish inland waters and four new maximum total lengths for the Seminemacheilus species. The results of this study provide useful information for further fisheries management, fish population dynamic studies and comparisons in future studies.

Modelling of transparency of Lake Baikal inferred from the Sentinel-2 Data

The remote sensing methods usage makes it possible to increase the accuracy and efficiency of data on the state of water bodies. Among the many satellite systems, Sentinel-2 is the most suitable for inland water assessment. One of the abiotic factors in assessing the trophicity of water bodies is the transparency along the Secchi disk. Models for calculating water transparency have been developed for individual water bodies. The analysis showed that these models don t adequately describe the transparency for Lake Baikal. Based on the correlation-regression analysis, the parameters of the exponential function were estimated for calculating the transparency of the surface waters of Lake Baikal using the values of the Sentinel-2 spectral channels. Despite the inaccuracy of the model for assessing the transparency in the coastal zone, it can be used to assess the seasonal and interannual transparency of the surface waters of Lake Baikal.

The variability of morphometric and meristic characteristics of Urmia chub, Petroleuciscus ulanus (G nther, 1899) in the Mahabd-Chai and Godar-Chai rivers, Lake Urmia basin

In this study, for the first time, we provide morphometric and meristic data on Petroleuciscus ulanus from the Lake Urmia basin by comparing them in the populations of the Mahabad-Chai and Godar-Chai rivers. For this purpose, a total of 100 specimens were collected using electrofishing device and cast net during 2014 and 2015. 19 morphometric and 8 meristic traits were measured and counted, respectively. The meristic traits of the two populations showed significant differences in three characters, including branched dorsal and ventral fin rays and lateral line scales (P<0.05). In addition, the morphometric analysis showed significant differences in head length, eye diameter, caudal peduncle length, dorsal fin height and base lengths, pectoral and ventral fin lengths, anal fin base and height lengths (P<0.05). The finding of the current study can help to further studies on the biological features of this endemic species of Iranian inland waters.