Savosin, Evgeny Sergeevich

Savosin E., Slukovskii Z.

Милянчук Н.П., Савосин Е.С., Кучко Я.А., Стерлигова О.П., Ильмаст Н.В.

В статье исследован состав бентофауны и рыбного населения озера Пандозера (бассейн Онежского озера), расположенного на территории Государственного природного заповедника «Кивач» (Республики Карелия). Количественные показатели макрозообентоса соответствуют олиготрофному типу водоемов, величина хирономидного индекса – умеренно- загрязненному водному объекту. Рыбное население озера представлено 13 видами рыб (6 семейств), среди которых преобладающими являются окунь, лещ и плотва. Отмечены ценные виды рыб: сиг и судак. Язь обнаружен в озере впервые. В целом проведенные исследования показали удовлетворительное состояние экосистемы оз. Пандозеро на современном этапе. The composition of the benthic fauna of the fish population of Pandozero Lake (Onega Lake basin), located in the Kivach State Nature Reserve, Republic of Karelia, was studied. The abundance indices of its macrozoobenthos are consistent with an oligotrophic type of water bodies, and its chironomid index value with that of a moderately contaminated water body. The lake’s fish population consists of 13 species (6 families) dominated by perch, bream and roach. Valuable fish species, such as whitefish and pike-perch, also occur. Ide was found in the lake for the first time. The studies have shown that Pandozero Lake’s ecosystem is now in satisfactory condition.

Baryshev I.A., Savosin E., Komulainen S.F.

ABSTRACT An assessment of the ecological state of the lake–river system of Eastern Fennoscandia in the European North of Russia has been carried out. It was found that in conditions of ultra-fresh waters with a high humus content, biotic indicators may indicate pollution of water bodies that do not actually experience significant anthropogenic impacts. Based on the indicators of macrozoobenthos and phytoperiphyton (indices such as FBI, EBI, BMVP, ASPT, BBI, IBGN, SI, GV, EPT, IB, IM, and TDI), a comprehensive assessment of water quality was given. Ratings ranging from ‘poor’ to ‘excellent’ were obtained for different stations, reflecting the influence of natural features of different sections of the river. ‘Good’ water quality was noted at the river rapids. For river reaches and lake biotopes, ‘mediocre’ water quality was revealed. The low anthropogenic load on the river catchment allows us to conclude that most indices for assessing water quality significantly underestimate the results in the natural conditions of Eastern Fennoscandia. The relatively poor natural fauna, low water salinity and high humus content can make it difficult to determine the level of anthropogenic pollution using biotic indicators. The most error-prone indices are GW and IBGN, of which the former overestimates and the latter underestimates.

Savosin E.S., Kuchko Y.A., Savosin D.S., Ilmast N.V., Milyanchuk N.P.

Based on our own and literature data, the state of the ecosystem of Lake Maloe Yanisjarvi (South Karelia) in the conditions of industrial trout farming (since 2020) has been analyzed. The reservoir belongs to the mineralized (24.4-31.6 mg/l), calcium sulfate class. The chemical composition of the waters is not subject to significant fluctuations throughout the year. Among the forms of mineral nitrogen, nitrate and ammonium predominate (the maximum concentration noted is 0.12 mg/l). The total phosphorus content does not exceed 0.012 mg/l, mineral – 0.01 mg/l. Fluctuations in the concentration of dissolved oxygen are in the range of 7.0-9.1 mg/l. High flow rate (indicator of conditional water exchange 3.5 year-1) is the main stabilizing factor contributing to the preservation of the hydrochemical regime of the reservoir. In general, the water masses of Lake Maloe Yanisjarvi in their chemical composition meet the requirements for the aquatic environment in the cage cultivation of salmon. The data on the main hydrological and hydrobiological indicators of the lake are presented. According to the level of quantitative development of zooplankton in the summer-autumn period, the lake corresponds to the oligotrophic type with a biomass of up to 1 g/m3, benthos – to the α-mesotrophic type (2.8 g/m2). The reservoir belongs to the highest fishery category, according to literature data, valuable fish species (salmon, trout, whitefish and grouse) are noted as part of the ichthyofauna. Recommendations on the timing of the ecological expertise of the lake are given.

Sterligova O.P., Savosin E.S., Kuchko Y.A., Savosin D.S., Milyanchuk N.P.

The article highlights the analyzes of the ecosystem of Lake Khedo (Republic of Karelia) under conditions of growing anthropogenic load caused by using the lake for breeding trout in fish cages based on the proper and literature data. Comparative analysis of hydrochemical data before the operation of the farm (until 2005) and after showed a twofold increase in water color (70-150°), which indicates an increased content of organic pollutants (humus, peat, silt). Also in the reservoir there are increased nitrogen and phosphorus compounds. Previously, the concentration of total phosphorus did not exceed 0.01 mg/l, today it reaches 0.02 mg/l. The main factor contributing to the satisfactory state of Lake Khedo is the high water flow rate, due to which most biogens are flown outside the lake. The data on the main hydrobiological indicators of the lake (phytozooplankton and zoobenthos) are presented. It has been stated that if earlier the reservoir corresponded to the mesohumous oligotrophic type, at present it reaches the initial level of mesotrophy, which is probably facilitated by the long-term cage cultivation of the aquaculture object. In terms of the abundance of organisms of the initial trophic levels, the reservoir corresponds to α-mesotrophic type. The lake is inhabited by 8 species of fish, and the valuable ones include whitefish Coregonus lavaretus (L.) and vendace Coregonus albula (L.). The results of the research made it possible to clarify the total production of commercial trout, which amounted to 300 tons per year and doesn’t exceed the total biogenic load. Recommendations on timing the regular ecological expertise of the lake and the adjustment of production volumes are given

Savosin E.S., Savosin D.S.

Ilmast N.V., Sterligova O.P., Kuchko Y.A., Sharov A.N., Savosin E.S., Savosin D.S.

The results of the study of the Lake Maslozero ecosystem (the White Sea basin) are reported. The lake is small, deep, and poorly lotic. Its hydrochemical and hydrobiological parameters were studied. The quantitative and structural characteristics of the state of zooplankton and macrozoobenthos in the lake are presented for the first time. The lake is an oligo-mesotrophic water body, as indicated by the nutrient content scale. The lake is inhabited by 14 fish species of 11 families. The perch Perca fluviatilis, the whitefish Coregonus lavaretus, the pike Esox lucius, the roach Rutilus rutilus, and the introduced smelt Osmerus eperlanus are the most abundant. The work on the introduction of smelt into Lake Maslozero is evaluated. The smelt in the lake has naturalized, is successfully reproducing, and has become abundant. Its growth rate is identical to that of the smelt from its parental water body, Lake Ladoga. The food ration of predatory fish (pike, burbot, perch, and char) is dominated by smelt as the most abundant and accessible food item available all year round. The lake is used by the local population for economic purposes, recreation, amateur fishing, and fish culture.

Rasputina E., Milyanchuk N., Ilmast N.

The feeding of perch (Perca fluviatilis) from the littoral zone of Ladoga Lake was studied. Attention was focused on the colonizer species, a Baikal amphipod (Gmelinoides fasciatus), and its contribution to feeding. The invasion of Ladoga Lake by the Baikal amphipod has provided a new food item accessible to the fish. The results of the study have shown that the habitat of perch is largely the same as that of the Baikal amphipod. The food of perch was found to consist of various bottom fauna representatives. The colonizer Baikal amphipod made up over 40% of the food bolus by weight, indicating its great contribution to perch’s feeding.

Ilmast N.V., Sterligova O.P.

Abstract The composition of the fish population of three water bodies in the Kenti River system (White Sea basin), polluted by waste from a mining concentration plant, was analyzed. Only four out of 12 fish species of the Kenti River system (pike, burbot, bleak and roach) occur in all the water bodies studied. The fish population is dominated by roach. Smelt and dace were shown to be most sensitive to industrial waste. The closer to the source of pollution, the smaller the number of fish species in the lake. The impoverishment of the fish fauna is largely due to its (alkaline) habitat and the loss of spawning and growing conditions for juveniles (small areas occupied by aquatic vegetation).

van Vliet M.T., Thorslund J., Strokal M., Hofstra N., Flörke M., Ehalt Macedo H., Nkwasa A., Tang T., Kaushal S.S., Kumar R., van Griensven A., Bouwman L., Mosley L.M.

Climate change and extreme weather events (such as droughts, heatwaves, rainstorms and floods) pose serious challenges for water management, in terms of both water resources availability and water quality. However, the responses and mechanisms of river water quality under more frequent and intense hydroclimatic extremes are not well understood. In this Review, we assess the impacts of hydroclimatic extremes and multidecadal climate change on a wide range of water quality constituents to identify the key responses and driving mechanisms. Comparison of 965 case studies indicates that river water quality generally deteriorates under droughts and heatwaves (68% of compiled cases), rainstorms and floods (51%) and under long-term climate change (56%). Also improvements or mixed responses are reported owing to counteracting mechanisms, for example, increased pollutant mobilization versus dilution during flood events. River water quality responses under multidecadal climate change are driven by hydrological alterations, rises in water and soil temperatures and interactions among hydroclimatic, land use and human drivers. These complex interactions synergistically influence the sources, transport and transformation of all water quality constituents. Future research must target tools, techniques and models that support the design of robust water quality management strategies, in a world that is facing more frequent and severe hydroclimatic extremes. Maintaining good water quality is vital for healthy ecosystems and human water use, yet water quality responses to hydroclimatic extremes and changing climate are poorly understood. This Review explores river water quality under climate change and extremes.

Mogane L.K., Masebe T., Msagati T.A., Ncube E.

AbstractFreshwater resources play a pivotal role in sustaining life and meeting various domestic, agricultural, economic, and industrial demands. As such, there is a significant need to monitor the water quality of these resources. Water quality index (WQI) models have gradually gained popularity since their maiden introduction in the 1960s for evaluating and classifying the water quality of aquatic ecosystems. WQIs transform complex water quality data into a single dimensionless number to enable accessible communication of the water quality status of water resource ecosystems. To screen relevant articles, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method was employed to include or exclude articles. A total of 17 peer-reviewed articles were used in the final paper synthesis. Among the reviewed WQIs, only the Canadian Council for Ministers of the Environment (CCME) index, Irish water quality index (IEWQI) and Hahn index were used to assess both lotic and lentic ecosystems. Furthermore, the CCME index is the only exception from rigidity because it does not specify parameters to select. Except for the West-Java WQI and the IEWQI, none of the reviewed WQI performed sensitivity and uncertainty analysis to improve the acceptability and reliability of the WQI. It has been proven that all stages of WQI development have a level of uncertainty which can be determined using statistical and machine learning tools. Extreme gradient boosting (XGB) has been reported as an effective machine learning tool to deal with uncertainties during parameter selection, the establishment of parameter weights, and determining accurate classification schemes. Considering the IEWQI model architecture and its effectiveness in coastal and transitional waters, this review recommends that future research in lotic or lentic ecosystems focus on addressing the underlying uncertainty issues associated with the WQI model in addition to the use of machine learning techniques to improve the predictive accuracy and robustness and increase the domain of application.

Slukovskii Z.

The article presents data on the analysis of U accumulation in recent sediments of lakes in the territory of the Southeast Fennoscandia. The research was carried out in the study area of the Republic of Karelia. It has been established that the content of U in sediments varies from 0.1 to 42.3 mg/kg (median is 0.91 mg/kg). In general, the studied sediments of the region had low concentrations of U in comparison with the average content of this element in the upper part of the Earth’s crust. In some areas associated with deposits or ore occurrences of U, an increased content of U in lake sediments was revealed. The highest U accumulation level was found in the lake sediments, which are under the influence of the North Onega ore-geochemical region, where V deposits and ore occurrences that contain U, Fe, Mo and Cu are widespread. In the sediments of some studied lakes, Th anomalies were found, which often accompany U in ore geological formations. The analysis of uranium fractions in the sediments of some lakes in Karelia revealed the key role of the mineral (insoluble) phase in the accumulation of U, up to 64–68% of the total U content. The share of the organic fraction in the accumulation of U in the studied sediments of the lakes is small and ranges from 7 to 15% with respect to the total concentration of the metal.

Yao S., Chen C., He M., Cui Z., Mo K., Pang R., Chen Q.

Land use and land cover (LULC) have significant impacts on river water quality, particularly in regions subjected to rapid urbanization. However, it is unclear whether LULC (LULC type and pattern index) can be used as an effective indicator to predict water quality over the rapid urbanization regions. Here, we investigated the spatiotemporal changes of LULC and their impacts on the water quality of a river flowing through a rapidly developed area in China. Then, a cellular automata-Markov model was established to predict the LULC, which was used as a key indicator to predict future water quality by a multiple linear regression model. The results showed that construction land experienced rapid growth between 2000 and 2010 taking over arable land to a great extent, and the number of patch (NP) showed a significant downward trend during 2000–2010. The biochemical oxygen demand in five days (BOD5), total nitrogen (TN), and total phosphorus (TP) exhibited significantly positive correlations with construction land, while dissolved oxygen (DO) showed a significantly negative correlation with construction land. The DO exhibited a significantly positive correlation with the number of patch (NP), but TN and TP showed significantly negative correlations with NP. The water quality prediction model based on LULC performed well, especially TN prediction has a coefficient of determination of 0.691 and a mean relative error of 12.14%. The prediction of water quality in 2030 indicated that TN will not increase further, but TP will exhibit a remarkable increase in Zhenjiang city if the current development trend continues and no extra pollution control measures are taken.

Slukovskii Z.

Lake sediments are a reliable source of information about the past, including data of the origin of water bodies and their changes. Russia has more than 2 million lakes, so paleolimnological studies are relevant here. This review deals with the most significant studies of sequential accumulation of pollutants, including heavy metals in recent lake sediments in Russia. The key areas are northwestern regions of Russia (Murmansk Region, the Republic of Karelia, Arkhangelsk Region), the Urals (Chelyabinsk Region, the Republic of Bashkortostan), and Siberia. The review presents the data of pollutants accumulation, the sedimentation rate in lakes in the anthropogenic period, and the key sources of pollution of the environment in each of the mentioned regions. The article is divided into three parts (sections): industrial areas, urbanized areas, and background (pristine) areas so that readers might better understand the specifics of particular pollution and its impact on lake ecosystems. The impact of metallurgical plants, mining companies, boiler rooms, coal and mazut thermal power plants, transport, and other anthropogenic sources influencing geochemical characteristics of lakes located nearby or at a distance to these sources of pollution are considered. For instance, the direct influence of factories and transport was noted in the study of lake sediments in industrial regions and cities. In the background territories, the influence of long-range transport of pollutants was mainly noted. It was found that sedimentation rates are significantly lower in pristine areas, especially in the Frigid zone, compared to urbanized areas and industrial territories. In addition, the excess concentrations of heavy metals over the background are higher in the sediments of lakes that are directly affected by the source of pollution. At the end of the article, further prospects of the development of paleolimnological studies in Russia are discussed in the context of the continuing anthropogenic impact on the environment.

Uddin M.G., Nash S., Rahman A., Olbert A.I.

In order to keep the "good" status of coastal water quality, it is essential to monitor and assess frequently. The Water quality index (WQI) model is one of the most widely used techniques for the assessment of water quality. It consists of five components, with the indicator selection technique being one of the more crucial components. Several studies conducted recently have shown that the use of the existing techniques results in a significant amount of uncertainty being produced in the final assessment due to the inappropriate indicator selection. The present study carried out a comprehensive assessment of various features selection (FS) techniques for selecting crucial coastal water quality indicators in order to develop an efficient WQI model. This study aims to analyse the effects of eighteen different FS techniques, including (i) nine filter methods, (ii) two wrapper methods, and (iii) seven embedded methods for the comparison of model performance of the WQI. In total, fifteen combinations (subsets) of water quality indicators were constructed, and WQI values were calculated for each combination using the improvement methodology for coastal water quality. The WQI model's performance was tested using nine machine-learning algorithms, which validated the model's performance using various metrics. The results indicated that the tree-based random forest algorithm could be effective for selecting crucial water quality indicators in terms of assessing coastal water. Deep neural network algorithm showed better performance for predicting coastal water quality more accurately incorporating the subset of the random forest.

Rana D., Joshi N.

Rivers being the natural resources, it is our duty to conserve them and protect them. But for protecting them we need to understand the parameters which are involved in polluting them. Ganges, being the holy river is mostly polluted. Hence, we need to protect it. Therefore, the need for the study is to revive the river ecology by converting them into a scientific method that will protect the river ecology. This study aims to assess the river Ganga's variations in water quality from Rishikesh to Haridwar, Uttarakhand, India. The data is collected from the five different sites lying in the route of Rishikesh to Haridwar. A scientific investigation was conducted in order to determine the influence of human interference in the ecology of river Ganga. Tapovan (Site-1), Raiwala (Site-2), Bhimgoda (Site-3), Devpura (Site-4) and Jagjeetpur (Site-5) were selected as the study and sampling sites which gives an indication of stricter implementation, management, monitoring and strengthening public awareness to safeguard river Ganga water quality.

Komulaynen S., Slastina J.

Data are reported about the formation of phytoplankton and phytoperiphyton communities in Lake Khedo (Karelia republic, White Sea catchment) under the effect of effluent discharges from a trout farm. The purpose of this paper is to assess how informative phytoperiphyton structural parameters are, and to assess the feasibility of using them for biological monitoring of river quality. The influence of anthropogenic impacts on periphyton communities was analyzed in terms of species richness, species diversity, species ecology values, biomass and chlorophyll concentration. At present, effluents discharged into the lake from the trout farm cause no profound transformations in the structure of aquatic organism communities. The results of the chemical analysis of water indicate a low level of anthropogenic influence. Although a slight increase in the concentration of suspended matter and heavy metals in the water near the cages was recorded. The structure of algae communities is due primarily to specific hydrographic location and hydrological characteristics of lake. The composition and ratio of most common species of algae communities in the lake is typical for cold-water, oligotrophic reservoirs of the boreal and subarctic zones, with low mineralization, not experiencing a significant anthropogenic load. The biotic indices and hydrochemical indicators indicated mainly a low degree of pollution, so the lake waters could be classified as belonging to water purity class II. Relatively high values of the abundance and biomass of phytoplankton and phytoperiphyton, in the Lake Khedo comparing to the average values for the studied region make it possible to conclude on the favorable conditions in the lake and on the stability of communities.

Slukovskii Z.I., Guzeva A.V., Dauvalter V.A.

Investigations of the rare earth elements (REEs) concentrations in surface sediments of small lakes in the Arctic zone of the Russian Federation are presented. The territories of Murmansk Region and the Republic of Karelia were used as key study areas. The sampling of 9 lake sediments was carried out. Inductively coupled plasma mass spectrometry (ICP-MS) method was used as a main approach to estimate total concentrations of REEs and heavy metals and content of their elements in different fractions, using sequential extraction method. The role of the natural landscapes factor (tundra, forest-tundra, taiga) in the process of REEs accumulation in lake sediments was evaluated in the course of the work. It was revealed that the highest median accumulation of REEs occurred in the sediments of lakes in the tundra zone, and the lowest median accumulation of REEs occurred in the lakes in the forest zone (taiga). The dynamics of the REEs accumulation in the lakes of the background (pristine) regions of the Arctic, as well as in the lakes of urbanized territories, is shown on the example of the cities of Murmansk Region. The analysis of the vertical distribution of REEs and heavy metals in the cores of sediments of the studied lakes showed that the anthropogenic factor plays an important role in the accumulation of REEs in urban water bodies. First of all, this is due to dust from construction, wear and tear of houses and road structures, and weathering of soils and quaternary deposits in urban areas. All urban lakes showed similarity between distribution of REEs and heavy metals in the sediments. The main fractions of REEs in the sediments of the lakes of the Arctic zone of Russia were determined. It was revealed that the residual phase of sediments and organic matter plays a significant role in the accumulation of REEs in surface sediments of the North of Russia. At the same time, mobile forms and phases of REEs associated with Fe and Mn oxides also did not play a large role in the accumulation of REEs in the sediments of lakes in Northwest Russia. • REE concentrations in lake sediments of northern and arctic regions were studied for the first time. • The sediments of the lakes of the tundra zone accumulate more REE than the lakes of the forest-tundra and the forest zone. • In urban lakes, REE can be indicators of technogenic impact on water bodies and the environment.

Kesti P., Hiltunen M., Strandberg U., Vesterinen J., Taipale S., Kankaala P.

Many lakes in the northern hemisphere are browning due to increasing concentrations of terrestrial dissolved organic carbon (DOC). The consequences of lake browning to littoral invertebrates, however, are not fully understood. We analyzed community structure and fatty acid (FA) profiles of littoral invertebrates in humic (DOC-rich) and clear-water lakes in Eastern Finland. We found higher abundance of chironomids (Diptera: Chironomidae) in humic compared to clear-water lakes, whereas stoneflies (Plecoptera) and mayflies (Ephemeroptera: Baetidae) were more abundant in clear-water lakes. Taxon explained 65% of the differences in the FA composition of littoral invertebrates. However, the proportion and content of polyunsaturated FAs of several taxa were significantly higher in clear-water lakes compared to humic lakes. Our results reveal differences in both community structure and nutritional quality of littoral invertebrates for fish between humic and clear-water lakes.

Baryshev I.A.

Macrozoobenthos analyses were used to evaluate the ecological water quality in the Shuya River, a large tributary of Onega Lake, which determines water chemistry in the water intake of Petrozavodsk City, the capital of the Republic of Karelia. Water quality indices, widely used in the world practice, were applied, including FBI, EBI, BMWP, ASPT, BBI, IBGN, GW, EPT, and IM, as well as the integral IBC index. At the average estimate good, the values of indices showed a strong dependence on the characteristics of the station. Samples taken in pool areas with soft soils gave underestimates of water quality indices. The quality classes moderate and good was found in small tributaries, and the quality class excellent, in rapids in the lower reaches of large rivers. It is recommended to evaluate water quality separately for pool areas, small tributaries, and rapids in the main channel; the obtained indices are recommended only to compare similar biotopes. The river ecosystem was found to be in a stable state, comparable with that in the 1980s, notwithstanding the heavier anthropogenic load.

Chertoprud M.V., Krylenko S.V., Lukinych A.I., Glazov P.M., Dubovskaya O.P., Chertoprud E.S.

The taxonomic structure, typology, species richness, and total abundance of bentic and littoral macroinvertebrate communities from small lakes of the Arctic and Subarctic zones are considered on the basis of original data from three northern Palearctic regions (the foot of the Putorana Plateau, Kolguev Island, and Western Svalbard Island). A comparative analysis of the communities of these regions has been carried out. The features of High Arctic insular, Low Arctic, subarctic, and boreal lake communities are discussed using a large volume of literature data. The complex pattern of changes in the total benthos biomass of small lakes has been revealed: it decreases in the subarctic taiga, increases in the hypoarctic tundra, and decreases again in the High Arctic.

Guzeva A., Slukovskii Z., Dauvalter V., Denisov D.

This paper presents the comprehensive evaluation of the level of accumulation of some of the most dangerous environmental pollutants (V, Co, Sn, Ni, Cr, Mn, Cd, Cu, Pb, Sb, Zn) and analyses their chemical forms in sediments of four small lakes located within Murmansk urban territory. Furthermore, the authors first studied morphology and chemical composition of industrial dust collected from the snow covering the ice of Lake Srednee. Fieldwork was carried out in April 2019. The results showed that sediments of the Murmansk urban lakes are significantly enriched in the content of the toxic metals and metalloids Cd, Pb, Sb, Zn, Cu, V, and Ni. An integrated assessment of anthropogenic impact using the pollution load index (PLI) and geoaccumulation index (Igeo) revealed a moderate to the extremely strong pollution level in recent sediment layers. The analysis of the fractions of the elements showed that they are mainly associated with stable compounds, such as primary minerals or persistent technogenic compounds (slag, matte, and dust). However, humic substances are a significant accumulative matrix for most studied elements. The share of the most mobile fractions does not exceed 30% for the vast majority of elements, even in the most polluted layers. The accumulation of the major part of pollutants can be attributed to the activities of the main industrial objects of the city (thermal power plant, coal port, transport infrastructure), and the impact of the global atmospheric transport of pollutants to the Arctic regions of Russia.

Slukovskii Z., Medvedev M., Mitsukov A., Dauvalter V., Grigoriev V., Kudryavtzeva L., Elizarova I.

The article presents the first data on the study of a wide range of chemical elements in the water and sediments of small lakes located in the Arctic Zone of Russia. Among the selected objects are two lakes located in the urbanized areas. As a result, the sediments of all lakes were classified by the ratio of the main elements and the total content of organic matter. The concentration coefficients of all elements were calculated taking into average concentrations of different elements in the continental crust and the potentially toxic elements in the sediments of the background area. Analyzing sediment cores made it possible to evaluate the historical dynamics of the behavior of some metals and metalloids (Pb, Cd, Sb, Sn, Bi, Ni, Cu) in the aquatic environment during the industrial era, both in urbanized territories and in the background regions of the Arctic. The main natural and anthropogenic factors of the formation of geochemical anomalies in the concentrations of different elements, including potentially toxic ones, in the sediments studied, were identified. In urban areas, the main sources of metals entering the lake environment are emissions of the copper–nickel, thermal power plants, coal port, and an incineration plant. For all lakes, the pollution level of objects was estimated by calculating the geo-accumulation index and pollution load index. The most polluted lakes are the lakes of urban areas of the Arctic, the lakes of the background territories are characterized by a moderate level of pollution or no pollution.

Ozoliņš D., Skuja A., Jēkabsone J., Kokorite I., Avotins A., Poikane S.

Highly humic lakes are typical for the boreal zone. These unique ecosystems are characterised as relatively undisturbed habitats with brown water, high acidity, low nutrient content and lack of macrophytes. Current lake assessment methods are not appropriate for ecological assessment of highly humic lakes because of their unique properties and differing human pressures acting on these ecosystems. This study proposes a new approach suitable for the ecological status assessment of highly humic lakes impacted by hydrological modifications. Altogether, 52 macroinvertebrate samples from 15 raised bog lakes were used to develop the method. The studied lakes are located in the raised bogs at the central and eastern parts of Latvia. Altered water level was found as the main threat to the humic lake habitats since no other pressures were established. A multimetric index based on macroinvertebrate abundance, littoral and profundal preferences, Coleoptera taxa richness and the Biological Monitoring Working Party (BMWP) Score is suggested as the most suitable tool to assess the ecological quality of the highly humic lakes.