Determination of the Physicochemical and Microbiological Index of the River Chakvistskali

The growing impact of the anthropogenic factors on the environment has intensified the importance of protecting the water ecosystem. The degrading of water resources is a frequent result of the anthropogenic eutrophication resulting in imbalance of substance levels and deterioration of sanitation and recreational condition of water. The environmental impact of contaminants is manifested at the level of organisms, populations, biocenosis, and ecosystems. In the context of the increased anthropogenic load, the growing contamination of water bodies impairs the self-cleansing capacity of water, causes eutrophication and reduces water quality.

New and rare species of algae in the plankton of the Ob River

According to the study of summer phytoplankton of the Ob River, 153 new species and intraspecific taxa(SIT) of algae from 8 divisions were found, including Cyanoprokaryota – 14, Dinophyta – 2, Chrysophyta – 17, Xantophyta –6, Euglenophyta – 34, Bacillariophyta – 2, Chlorophyta – 72, Charophyta – 6. New taxa are dominated by small-cell greenalgae, phytoflagellates and non-heterocyst cyanoprokaryotes. The intensive succession of the phytoplanktocenosis speciescomposition and the taxonomic structure of the new SIT algae are signs of anthropogenic eutrophication.

CYPRINID FISH INFECTION WITH METACERCARIAS OF TREMATODES UNDER ANTHROPOGENIC EFFECT

We presented parasitological studies of fish (Cyprinidae) in the Usman River within the Voronezhsky Biosphere Reserve. The infection of fish with metacercarias of trematodes in the river sections with various anthropogenic effect was assessed. We identified metacercarias of 6 species of trematodes: Opisthorchis felineus, Pseudamphistomum truncatum, Metorchis bilis, M. xanthosomus, Posthodiplostomum cuticola, and Paracoenogonimus ovatus. The highest occurrence and abundance of P. cuticola (95.4%, 36.4 sp.) and P. ovatus (56.9%, 8.8 sp.) was noted in the upper reaches of the River, in areas with high anthropogenic impact. An increased prevalence of infection was recorded for the group Opisthorchiidae (O. felineus, P. truncatum, and M. bilis) in areas within the Reserve with minimal anthropogenic impact. Infection rate of Opisthorchiidae metacercarias was 86.5% and 8.2 specimens in the middle and lower reaches of the River. At the same time, we noted a decrease in infection with P. cuticola (54.5%; 5.8 sp.) and P. ovatus (33.9%; 1.3 sp.). The degree of anthropogenic eutrophication of the Reservoir affects the development of different species of mollusks and the infection of fish with metacercarias. Metacercarias of trematodes can be used as indicators of water pollution in assessing anthropogenic effect on natural ecosystems.

Short-term changes of anthropogenic eutrophication with precipitation in tropical coastal waters (Guanabara Bay, Rio de Janeiro, Brazil)

<p>Eutrophication in coastal waters caused by non-treated urban discharges has been considered one of the most important effects of global change. At tropical latitudes, nutrient dynamics may be especially intense due to increased metabolic responses supported by high temperatures and solar incidence throughout the year. In addition, short-term variations, such as in rainfall and the tidal regime, may determine important changes in nutrient concentrations and the subsequent trophic status of coastal waters, which are still neglected especially during nocturnal periods due to common logistical constraints. Here, we assessed 24-h variations of water quality during the winter season in a tropical eutrophic bay that receives large inputs of nutrients from non-treated urban effluents (Guanabara Bay, RJ, Brazil). We measured concentrations of dissolved forms of nutrients (nitrate, nitrite, N-ammoniacal, phosphate, and silicate) and carbon (DOC), and oxygen (DO) associated with temperature, salinity, and pH in surface waters each 2h over two daily cycles (July and August 2018). Water samples for nutrients and DOC were preserved for later analysis, while other variables were measured in the field. A biomonitoring system with a submersible pump was used to collect surface coastal waters without bubbling, and along a 70 m pipe from the beach to the field lab. In turn, meteorological data were obtained from a city weather station located ~6 Km from the sampling area. The monthly accumulated precipitation with respect to the 24-h cycle in July was ~70% lower than in August (58 and 16 mm, respectively), although only that in July has showed a rainfall event during the sampling period. As a result, average DOC and N-ammoniacal concentrations in surface waters were ~50% lower, while nitrate, silicate and DO concentrations ~56, 164 and 50 % higher, respectively, during the 24-h cycle in August compared to July. Also, waters were slightly more basic and less saltier in August, contrasting with similar average values of phosphate concentrations and temperature between both sampling periods. Finally, DO concentrations indicated an intense metabolism, varying from a peak of supersaturation with high solar incidence to net autotrophy (2 pm) to undersaturation values as a proxy of net heterotrophy after the nocturnal period (6 am). In conclusion, this short-term study showed that higher monthly accumulated precipitation may dilute high DOC and N-ammoniacal concentrations in coastal aquatic ecosystems undergoing anthropogenic eutrophication. On the other hand, silicate and nitrate concentrations might be related to higher runoff inputs from the watershed. The event of precipitation in July also confirmed a drastic increase in nitrate concentrations, likely due to inputs from the watershed. Therefore, our findings reveal the complexity of accumulated and immediate effects of rainfall on nutrient levels in tropical coastal waters, which  highlight the importance of biomonitoring studies specially in urban areas.</p>

Mechanisms behind bottom-up effects: eutrophication increases fecundity by shortening the interspawning interval in stickleback

Anthropogenic eutrophication is altering aquatic environments by promoting primary production. This influences the population dynamics of consumers through bottom-up effects, but the underlying mechanisms and pathways are not always clear. To evaluate and mitigate effects of eutrophication on ecological communities, more research is needed on the underlying factors. Here we show that anthropogenic eutrophication increases population fecundity in the threespine stickleback (Gasterosteus aculeatus) by increasing the number of times females reproduce—lifetime fecundity—rather than instantaneous fecundity. When we exposed females to nutrient-enriched waters with enhanced algal growth, their interspawning interval shortened but the size of their egg clutches, or the size of their eggs, did not change. The shortening of the interspawning interval was probably caused by higher food intake, as algae growth promotes the growth of preferred prey populations. Enhanced female lifetime fecundity could increase offspring production and, hence, influence population dynamics. In support of this, earlier studies show that more offspring are emerging in habitats with denser algae growth. Thus, our results stress the importance of considering lifetime fecundity, in addition to instantaneous fecundity, when investigating the impact of human-induced eutrophication on population processes. At a broader level, our results highlight the importance of following individuals over longer time spans when evaluating the pathways and processes through which environmental changes influence individual fitness and population processes.

Assessment of Freshwater Bodies in Murmansk in Terms of Composition of Aquatic Invertebrates

The paper presents the results of analysis of hydrobiological samples of freshwater bodies of Murmansk (Lake Okunevoe, Lake Ledovoe and Lake Semyonovskoe). The number, degree of dominance and frequency of occurrence of organisms are determined. In Lake Ledovoe, the dominant species represent small organisms with simple life cycles and a high rate of reproduction. The taxonomic composition of water invertebrate community in the Lake Ledovoe highlights features of anthropogenic eutrophication. Several dominant species stand out in the ciliatocenosis of the Lake Okunevoe. The species diversity of micrzooplankton community is higher than in the Lake Ledovoe. In general, the Lake Okunevoe can be characterized as a water body with signs of ecosystem stability damage. The hydrobiocenoses of the Lake Semyonovskoe has the greatest species diversity. However, it is characterized by the tendency to decrease the species composition of organisms – indicators of clean waters. There are initial signs of anthropogenic eutrophication of the Lake Semyonovskoe. The waters of the studied lakes are characterized as β-mesosaprobic (moderately contaminated). It is generally noted that the fauna of water bodies is characterized by small species diversity. In lakes, there is a prevalence of small-sized organisms of heterotrophic nutrition. There is a stable decreasing tendency of species composition of hydrobionts and simplification of food chains in urban aquatic ecosystems subject to anthropogenic impact.

NIGHT MIGRATION COMPLEX OF ENDEMIC AMFIPOD AS AN INDICATOR OF ENVIRONMENTAL STATE BAIKAL LAKE

With the ongoing anthropogenic eutrophication of the Lake Baikal there is an increase in the abundance not only of aquatic vegetation, but also organismsconsumers. As consumers of vegetable detritus are crustaceans – amphipods, which, by eating detritus, partially reduce the pollution of the lake with rotting organic matter. A significant increase in their number is evidenced by the increase in the abundance of amphipods in the nocturnal migratory complex in the coastal pelagic zone.