Natalia A. Gashkina

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The bioaccumulation of elements in the organs and tissues of the whitefish (Coregonus lavaretus L.) from various stretches of Imandra Lake under anthropogenic influence in the toxic load reduction period is considered. The accumulation of elements in the whitefish’s organs and tissues depends to a lesser extent on higher concentrations of toxic elements and the physiological state in water and to a greater extent on the tolerance thereto. The element redistribution in the whitefish’s liver and kidney in terms of its physiological state is modeled. The adaptive response strategy is observed most clearly in changes in iron and zinc metabolism.

Metals are dispersed in natural environments, particularly in the aquatic environment, and accumulate, causing adverse effects on aquatic life. Moreover, chronic polymetallic water pollution is a common problem, and the biological effects of exposure to complex mixtures of metals are the most difficult to interpret. In this review, metal toxicity is examined with a focus on its impact on energy metabolism. Mechanisms regulating adenosine triphosphate (ATP) production and reactive oxygen species (ROS) emission are considered in their dual roles in the development of cytotoxicity and cytoprotection, and mitochondria may become target organelles of metal toxicity when the transmembrane potential is reduced below its phosphorylation level. One of the main consequences of metal toxicity is additional energy costs, and the metabolic load can lead to the disruption of oxidative metabolism and enhanced anaerobiosis.

The mechanisms of biogeochemical adaptation of fish to survival in the historically contaminated Imandra Lake were studied. The role of trace elements in the protective functions of the organism and their importance in the readaptation of organisms to improving the habitat was established. An elevated S to Se ratio indicates a high antioxidant status of fish from the historically contaminated part of the lake, while an increased accumulation of Fe, Cu, and Se can serve as a marker of liver pathologies, and of Zn and Co, of kidney pathologies.

Small lakes are potentially effective environmental sensors; they react quickly to anthropogenic stressors. We studied the long-term response of water chemistry to reduced acid deposition and climate warming in the Kola Arctic region of Russia based on monitoring data from 75 lakes. Monitoring was carried out once every 4–5 years in 1990–2018, with analysis for major anions and cations, dissolved organic carbon (DOC), and heavy metals (Ni and Cu). Analysis of archive data on the weather allowed us to reliably identify trends toward a systematic temperature increase over the past 28 years. The population of the lakes under study was proven to generally show a decrease in the concentrations of anthropogenic sulfates and the strengthening of the acid-neutralizing capacity (ANC) of the waters during this period. The concentrations of both DOC and nutrients (P_tot and N_tot) in the lake waters were determined to increase. This phenomenon can be explained by the following two mechanisms: a decrease in the deposition of strong acids and climate warming. We suggest that the effects of multiple factors on the surface waters result in an irreversible evolution of the lakes; hence, the term recovery does not adequately reflect the processes occurring in this industrially well-developed part of the Arctic.

The mechanisms of fish adaptation to survival in the historically contaminated Lake Imandra were studied. The role of trace elements in the protective functions of the organism and their importance in the re-adaptation of organisms to improving the habitat was established. The lake whitefish (Coregonus lavaretus L.) unable to migrate for large distance was chosen as the object of research. The indices of red blood as an indicator of fish homeostasis, as well as the role of white blood cells in the activation of the immune system were examined. The causes of the occurrence of histopathologies of organs and tissues are explained. Data on the accumulation of trace elements in the body of fish from this lake are presented. The principal difference in the bioaccumulation of elements is the intense metabolism of Se. An elevated S to Se ratio indicates a high antioxidant status of fish from the historically contaminated part of the lake, while an increased accumulation of Fe, Cu, and Se can serve as a marker of liver pathologies, and Zn and Co, of kidney pathologies.

Kola nuclear power plant, which discharges warm water into one of the bays of sub-arctic Lake Imandra, significantly changes the fish habitat, creating temperature gradient from 2 to 8°C compared to water temperature in the other part of the lake. The permeation, metabolism and bioaccumulation of elements in the stenothermal cold-water species (Coregonus lavaretus L.) in warm water impact zone are characterized. One of the main adaptation mechanisms of ionic regulation is the intense metabolism of Na due to the high respiratory activity of whitefish in warmer water. This feature is associated with elevated accumulation of Rb and loss of Se, Mo, and Si. At elevated temperatures, the main metabolic need is caused by Se deficiency. An extensive metabolism of selenoproteins involves risks of toxic effects and bioaccumulation of Hg, As and Cu with an increase of existing stressor or appearance of new ones.

The Kola nuclear power plant, which discharges warm water into one of the bays of subarctic Lake Imandra, significantly changes fish habitats. The temperature gradient of the lake is between 2 and 8 °C, which makes it significantly different from the natural temperature of the lake water. The stenothermal cold-water native species (lake whitefish (Coregonus lavaretus L.)), living for more than 40 years under conditions of thermal pollution, has adapted to this stressor. Moreover, this population differs favorably from the population in the natural-temperature environment in terms of its physiological state. Firstly, the hemoglobin concentrations in the fish blood are in the range of the ecological optimum, and secondly, it has a higher somatic growth, as estimated by Fulton’s condition factor. One of its main adaptive mechanisms of ion regulation is an intense metabolism of Na due to the high respiratory activity of the whitefish in warmer water. An increased accumulation of Rb and excretion of Se, Mo, and Si are associated more or less with that feature. Under conditions of an increased water temperature, the main metabolic need is due to a deficiency of Se in fish. The intensive metabolism of selenoproteins may involve risks of toxic effects and the bioaccumulation of Hg, As, and Cu in cases of increased existing stressors or the appearance of new ones.