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The study presents a bioindication complex and a technology of the experiment based on a submersible digital holographic camera with advanced monitoring capabilities for the study of plankton and its behavioral characteristics in situ. Additional mechanical and software options expand the capabilities of the digital holographic camera, thus making it possible to adapt the depth of the holographing scene to the parameters of the plankton habitat, perform automatic registration of the “zero” frame and automatic calibration, and carry out natural experiments with plankton photostimulation. The paper considers the results of a long-term digital holographic experiment on the biotesting of the water area in Arctic latitudes. It shows additional possibilities arising during the spectral processing of long time series of plankton parameters obtained during monitoring measurements by a submersible digital holographic camera. In particular, information on the rhythmic components of the ecosystem and behavioral characteristics of plankton, which can be used as a marker of the ecosystem well-being disturbance, is thus obtained.

To better understand freezing - thawing cycles operating in peat soils of permafrost landscapes, we experimentally modelled bi-directional freezing and thawing of peat collected from a discontinuous permafrost zone in western Siberia. We measured translocation of microorganisms and changes in porewater chemistry (pH, UV absorbance, dissolved organic carbon (DOC), and major and trace element concentrations) after thawing and two-way freezing of the three sections of 90-cm-long peat core. We demonstrate that bi-directional freezing and thawing of a peat core is capable of strongly modifying the vertical pattern of bacteria, DOC, nutrients, and trace element concentrations. Sizeable enrichment (a factor of 2 to 5) of DOC, macro- (P, K, Ca) and micro-nutrients (Ni, Mn, Co, Rb, B), and some low-mobile trace elements in several horizons of ice and peat porewater after freeze/thaw experiment may stem from physical disintegration of peat particles, leaching of peat constituents, and opening of isolated (non-connected) pores during freezing front migration. However, due to the appearance of multiple maxima of element concentration after a freeze-thaw event, the use of peat ice chemical composition as environmental archive for paleo-reconstructions is unwarranted.

Earlier, we showed that the registration of the behavioral responses of autochthonous mesozooplankton communities in situ is a more dynamic methodological approach in the biological assessment of the environmental well-being of aquatic ecosystems, as well as an alternative method to generally accepted tests on mortality and immobilization. The change in behavioral responses, including phototropic responses, may occur at lower concentrations of pollutants, leading to the inhibition of the risk-avoidance response of predatory fish attack and, ultimately, to the change in zooplankton abundance and biodiversity. The biological significance of such changes is quite high since zooplankters form the basis of food chains. This work studies the possibility of biomonitoring the quality of fresh water in Lake Baikal according to the state of the autochthonous mesozooplankton community in summer and winter using a digital holographic camera developed and tested by us in laboratory conditions. This method makes it possible to determine the concentration of plankters in the controlled volume of the DHC and perform photostimulation with different levels of illuminance. The depth profilometry of the phototropic response was compared with the profilometry of plankton concentration, intraspecific diversity of crustaceans according to the Pielou index, and the results of catching using the Juday net in the natural environment of the lake and during the modeling of the anthropogenic impact (introduction of table salt solution into the local area close to the registration probe). The circadian rhythm parameters were determined by the spectral analysis of the long-term registration of the phototropic response dynamics. It was noted that the inhibition of the phototropic response was the most adequate marker of the exogenous impact and the appearance of an alternating factor among the studied indicators of the state of the plankton community, namely, intraspecific diversity, synchronism of circadian rhythms, and response to paired photostimulation. The revealed patterns of behavioral responses of autochthonous zooplankton in natural and artificially modified conditions will allow for the implementation of long-term continuous control over the environmental well-being of water areas, including the collection ponds of treatment facilities, cooling ponds of nuclear power plants, and other water areas in contact with potentially hazardous facilities. The comparison of the identified patterns with the behavioral responses of euryhaline mesozooplankton will expand this method to assess the well-being of salt-water and marine reservoirs under the anthropogenic impact and will make it possible to create a continuous monitoring system.

The behavioral responses of autochthonous organisms have recently been used for a system to monitor the state of fresh and sea waters for bioindication. The advantage of using the behavioral responses of mesozooplankton is determined by the higher sensitivity of such responses compared with changes in the composition of biota or the death of organisms. Earlier, we developed and tested in laboratory conditions and in freshwater reservoirs a submersible digital holographic camera as part of a hydrobiological probe, which allows one to determine the dimensions, shape and recognition of plankters in situ, as well as define the concentration of plankters in the working volume and perform photostimulation with attractive radiation with different levels of illuminance. This paper presents the data obtained during the expedition to the Barents Sea. The variability with regard to the immersion depth of the phototropic response and the interspecific and intraspecific diversity was determined. It was shown that within the framework of natural variability in natural factors (temperature, salinity, hydrostatic pressure, oxygen content, illumination) there are no reliable changes in the indicator response, unlike changes in the concentration of plankton associated with tidal currents. The anthropogenic distortion of water quality was modeled by introducing a saturated salt solution dropwise. There were no significant changes in the intraspecific and interspecific diversity index during the external impact, and the rhythms of tidal changes in the concentration of plankters were suppressed. The fact of increased phototropic sensitivity in crustaceans with a size of less than 120 μm was found. It was established that the most essential marker of the alternating factor was the suppression of the phototropic response. The identified patterns of behavioral responses of autochthonous zooplankton make it possible to create a network of continuous control over the environmental health of water bodies subject to increased anthropogenic impact (oil production zones beyond the Arctic Circle, estuaries and deltas of rivers carrying industrial waste).

Our earlier studies showed that paired photostimulation allows the detection of pollutants in an aqueous medium according to the behavioral responses of freshwater Crustacea. The first stimulus initiated and stabilized the behavioral response. The increase in response to the second stimulus made it possible to assess the responsiveness of the zooplankton community. This paper studies the validity of this method for the detection of micro- and nanoplastic contamination of saltwater reservoirs according to the behavioral response of Artemia salina and Moina salina crustaceans. The studies were conducted in laboratory conditions using a submersible holographic camera developed by us, which ensures the in situ detection of the concentration and speed of crustaceans in a volume of up to 1 dm3, as well as makes it possible to change the intensity and duration of the attracting light. It was established that the phototropic response of crustaceans decreases in seawater at the cumulative dose of exposure to microplastics—0.15 mg∙dm−3∙h and nanoplastics—0.3 mg∙dm−3∙h. The paired photostimulation reveals the altering effect of micro- and nanoplastics in the saltwater medium no later than 3 h after their appearance, which indicates the promising potential of this method for the alarm response in monitoring the environmental well-being of water bodies.

Current trends in the application of bioindication methods are related to the use of submersible tools that perform real‐time measurements directly in the studied aquatic environment. The methods based on the registration of changes in the behavioral responses of zooplankton, in particular Crustaceans, which make up the vast majority of the biomass in water areas, seem quite promising. However, the multispecies composition of natural planktonic biocenoses poses the need to consider the potential difference in the sensitivity of organisms to pollutants. This paper describes laboratory studies of the phototropic response of plankton to attracting light. The studies were carried out on a model natural community that in equal amounts includes Daphnia magna, Daphnia pulex, and Cyclops vicinus, as well as on the monoculture groups of these species. The phototropic response was initiated by the attracting light with a wavelength of 532 nm close to the local maximum of the reflection spectrum of chlorella microalgae. Standard potassium bichromate was used as the model pollutant. The largest phototropic response value is registered in the assemblage. The concentration growth rate of crustaceans in the illuminated volume was 4.5 ± 0.3 ind (L min)−1. Of the studied species, the phototropic response was mostly expressed in Daphnia magna (3.7 ± 0.4 ind (L min)−1), while in Daphnia pulex, it was reduced to 2.4 ± 0.2 ind (L min)−1, and in Cyclops vicinus, it was very small—0.16 ± 0.02 ind (L min)−1. This is caused by peculiar trophic behavior of phyto‐ and zoophages. The addition of a pollutant, namely potassium bichromate, caused a decrease in the concentration rate of crustaceans in the attracting light zone, while a dose‐dependent change in phototropic responses was observed in a group of species and the Daphnia magna assemblage. The results of laboratory studies showed high potential of using the phototropic response of zooplankton to monitor the quality of its habitat thus ensuring the early diagnostics of water pollution. Besides, the paper shows the possibility of quantifying the phototropic response of zooplankton using submersible digital holographic cameras (DHC). This paper describes laboratory studies of the phototropic response of plankton to attracting light. The studies were carried out on a model natural community that in equal amounts includes Daphnia magna, Daphnia pulex, and Cyclops vicinus, as well as on the monoculture groups of these species. The phototropic response was initiated by the attracting light with a wavelength of 532 nm close to the local maximum of the reflection spectrum of chlorella microalgae. The results of laboratory studies showed high potential of using the phototropic response of zooplankton to monitor the quality of its habitat thus ensuring the early diagnostics of water pollution.

The paper is devoted to studying the stability of of dispersed systems (DS) of nanoparticles (NP) of nickel (nNi), platinum (nPt), titanium dioxide (nTiO2), zinc oxide, multicomponent nanopowder (MNP) and multi-walled carbon nanotubes (MWCNT), formed basing on the growth media used in bioassay with application of aquatics: bacterial test-cultures Ecolum, Photobacterium phosphoreum and Escherihia coli, unicellular algae Chlorella vulgaris Beijer, infusoria Paramecium caudatum, cladocera Daphnia magna Straus and Ceriodaphnia affinis, fish Danio rerio. In the process of establishing a test-system the increase in the initial nanosubstance concentration of more than 5 mg/l results in the increase in the speed of aggregation of NP into DS and the decrease in their final concentration. We suggest the variants of estimation of effective concentration of NP in long-term biotesting.

Biological effects and ecotoxicity of NPs CeO2 with particle size Δ50 =16 nm and hydrobionts tolerance was measured in simulation based on test-reactions of a group of organisms representing major trophic levels of aquatic ecosystem. Biological activity of NPs CeO2 was noted against bacterial biosensor Ekolum, Сhlorella v. B., Paramecium c., Daphnia m. S. and Danio r. Toxicity and hazard level of NPs CeO2 were measured using biotesting and hydrobionts. Toxicity of NPs CeO2 against luminescent bacteria Ekolum and Paramecium c. and Danio r. was not established (L(E)С50 > 100 mg/l). In accordance with SGS and EC 93/67/EEC, NPs CeO2 is considered highly toxic (acute toxicity Level 1). Biomarkers and NPs CeO2 tolerant hydrobionts were determined. Range of tolerance of hydrobionts to NPs was established. The upper limit of tolerance was determined for certain hydrobionts by values of L(E)С50: 0.009 mg/l (by volume of Chl a) for Сhlorella v. B. and 46.15 mg/l (by mobility) for Daphnia m. S.

An assessment was performed to estimate ecological and biological effects of metallic and binary NPs of various chemical nature and structural characteristics. Application of rapid toxicity tests using hydrobionts of various trophic levels (E. coli, Сhlorella v. B., Paramecium c., Daphnia m. S., Danio r.) allowed to determine resistance range to NPs Ni, Pt, ZnO and CeO2. It was established that test reaction to contamination of water with NPs and development of adverse effects to phyto- and zooplankton is contingent on NPs physicochemical properties and sensitivity of hydrobionts. Concentrations of NPs not causing observed change of test reactions were determined. Chlorella v. B. was established to be the most vulnerable to contamination of medium with NPs; photosynthetic pigment quantity was determined to be the most sensitive parameter: nCeO2 L(E)С10 = 0.0007 mg/l, nNi L(E)С10 = 0.0015 mg/l, nZnO L(E)С10 = 0.0048 mg/l, nPt L(E)С10 = 0.033 mg/l. The highest resistance (L(E)С10 > 100 mg/l) to contamination shown by: E. Coli, Daphnia m. S., Danio r. to nPt ; Danio r. to NNi and nZnO, E. Coli, Paramecium c. to nCeO2; and Danior r. by the parameter ‘embryotoxicity’. The most vulnerable chains of trophic structure of communities were revealed as well as ways of disrupting food pyramid of an aquatic system. Range of resistance or range of concentrations within which biota retains resistance was shown to be an integral characteristic of NPs effects on ecosystems.

Our previous studies showed that the change in the plankton response to light could be an indicator of environmental pollution. This study experimentally reveals that the response of Daphnia magna Straus and Daphnia pulex plankton ensembles to photostimulation depends on the intensity of the attracting light. This makes it difficult to identify the occurrence and change of pollutant concentration. The large variability in the magnitude of the behavioral response is caused by the nonlinear response of plankton ensembles to the intensity of the attractor stimulus. As the intensity of the photostimulation increases, the variability of the phototropic response passes through increase, decrease, and relative stabilization phases. The paper proposes a modification of the photostimulation method—paired photostimulation involving successive exposure to two photostimuli of increasing intensity. The first stimulus stabilizes the behavioral response, while the increase in response to the second stimulus makes it possible to more accurately assess the responsiveness of the plankton ensemble. The paper studies the sensitivity of the method of paired stimulation of the behavioral response of different types of freshwater plankton ensembles: Daphnia magna Straus, Daphnia pulex to the effects of pollutants (potassium bichromate, microplastic). The study demonstrates good reliability and increased sensitivity of this method of detecting changes in environmental toxicity compared to single photostimulation or traditional bioindication through the survival rate of test organisms.