‘Ecological photobiology’ session of the Russian Photobiology Society 9^th Congress (Shepsi, September 12–19, 2021)

Abstract

‘Ecological photobiology’ session of the Russian Photobiology Society 9th Congress was devoted to a wide range of problems related to the assessment of the environmental state by photobiological methods and included oral presentations and a poster session. A short survey of these presentations is given.

The session ‘Ecological photobiology’ covered a wide range of problems related to the assessment of the environment status by photobiological methods and included oral presentations (reports by Prof. S. Pogosyan and O. Koksharova were made online), and a poster session, which was accompanied by an active discussion. All materials of the presentations are published in the Proceedings of the IX Congress of the Russian Photobiology Society (2021).

The multiplicity and diversity of factors constituting the environment require a search for integral characteristics to assess environmental risks for humans and ecosystems. Integral characteristics that can be used as a readout of the ecological state of the environment can be provided by biotesting and/or bioindication, which are important tools for detecting changes in the environment, either positive or negative, and their downstream effects on human society. Toxicity level of the environment is one of the main parameters of interest in assessing environmental health of an ecosystem. For such an assessment, it is rational to use bioassay, when a well-studied laboratory object is placed in the environment under study and its reaction is observed. Noninvasive optical measurement methods proved to be informative for environmental monitoring, allowing rapid assessment of the state of the ecosystem based on data from continuous measurements of photosynthetic characteristics of bioindicator organisms: higher plants for terrestrial ecosystems and microalgae for aquatic ecosystems.

One of the most successful methods of an integral assessment of medium toxicity is testing it with photobacteria. Luminescent bacteria combine various types of sensitive structures subject to damage (cell membrane, metabolic reactions, genetic apparatus). Therefore, the bioluminescent reaction can be influenced by toxic substances of different nature and mechanisms of action.

The method of assessing the state of the photosynthetic apparatus of plant objects based on the characteristics of chlorophyll fluorescence is particularly informative for biotesting for the toxicity of the environment. The photosynthetic apparatus is a complex system of reactions in which, under the action of very intense, saturating light the sequential reduction of electron carriers occurs up to the complete reduction of the entire electron transport chain. Changes in the quantum yield of chlorophyll fluorescence under the action of high-intensity light (fluorescence induction curve) reflect the kinetics of reduction of electron carriers of photosynthetic apparatus. The ratio of the initial value of the fluorescence quantum yield (at a weak testing excitation) to the maximum quantum yield (at the complete reduction of carriers) is a salient indicator of the efficiency of photosynthesis. Toxins lead to disruption of the photosynthetic apparatus, which is readily visible in changes of the characteristics of the fluorescence induction curve. The equipment is simple, sensitive, and affordable. The measurement takes a few seconds. A number of studies on this topic were presented at the Congress.

A number of reports were devoted to general issues of the application of optical methods to study the state of the photosynthetic apparatus and the use of optical measurement results to assess the state of ecosystems. In the plenary lecture by Prof. S. Pogosyan (Lomonosov Moscow State University), the possibilities of using chlorophyll absorption and fluorescence measurement methods for studying photosynthetic organisms were reviewed. Fresh and marine waters appear the most important objects that require environmental monitoring. Phytoplankton is the most suitable for the role of a reporter system reflecting the state of the aquatic environment. The concentration and species composition of the phytoplankton community and the rate of its production are the main indicators in assessment of the ecological state of water areas. Employment of biophysical approaches has made a significant contribution to the study of the environmental state of the water bodies. In his lecture, Prof. S. Pogosyan discussed phytoplankton communities characterizing the state of aquatic ecosystems. He also informed on the results of the recent research voyages of the Institute of Oceanology of the Russian Academy of Sciences, during which a method for measuring the absorption spectra of substances dissolved in water, as well as phytoplankton cells, was improved.

New technical and software solutions for a comprehensive assessment of photosynthetic parameters of microalgae in photobiotechnology and environmental monitoring were presented in the conference report by Dr. T. Antal et al. (Pskov State University, Lomonosov Moscow State University). Long-term observations of photosynthetic characteristics make it possible to analyze the dynamics of these changes under stress conditions. The analysis of large data samples requires development of new experimental protocols and data processing methods. Dr. S. Khruschev et al. (Lomonosov Moscow State University) presented a new method for analyzing the dynamics of the response of photosynthetic apparatus to the action of stressors based on the induction of chlorophyll fluorescence.

Several presentations demonstrated the results of studying various types of stresses by optical and other biophysical methods. Thus, in the report by Dr. T. Plyusnina et al. (Lomonosov Moscow State University), the dynamics of photosystem II heterogeneity during mineral starvation was discussed. The Lobachevsky State University of Nizhny Novgorod presented several works in which photosynthetic parameters of plants were studied under various types of stress as follows: under heat stress and soil drought (Dr. L. Yudina et al.), under the influence of magnetic fields (E. Gromova et al.), and under radioactive irradiation (M. Grinberg et al.).

The photosynthetic apparatus is a sensitive target for the most common and dangerous toxicants—heavy metals. In chloroplasts, heavy metals block the transport of electrons in different parts of the electron transport chain, affect the operation of photosystem II, reduce the efficiency of primary photochemical reactions, slow down the rate of photophosphorylation, and inhibit the dark reactions of photosynthesis. Several presentations were devoted to the results of studying by optical methods the characteristics of the photosynthetic apparatus of woody plants (A. Khmarik et al., St. Petersburg), peas (Dr. D. Todorenko et al., Lomonosov Moscow State University, Pskov State University), and photosynthetic apparatus of algae (Prof. D. Matorin et al., Lomonosov Moscow State University). To detect the presence of heavy metals from the data of multiple automatic measurements of chlorophyll fluorescence induction curves, special techniques for processing large data arrays are required. In the reports by Dr. S. Khruschev et al. and D. Kiseleva et al. (Lomonosov Moscow State University), the use of machine learning methods and artificial neural networks to analyze arrays of experimental data from photobiological observations in order to monitor the environment was demonstrated.

Dr. O. Koksharova (Lomonosov Moscow State University, Kurchatov Institute National Research Centre) presented data on the regulatory effect of bacterial metabolites on the photosynthesis processes in microalgae. For the first time, the specific effect of bacterial ketones on the functioning of photosystems in cyanobacteria cells was shown. Moreover, the regulatory effect of the toxic non-protein amino acid β-N-methylamino-l-alanine (BMAA) on the photosynthesis of cyanobacteria was revealed. BMAA leads to a sharp decrease in the content of 18 proteins in cells of diazotrophic cyanobacteria. These proteins are part of the complexes of both photosystem complexes, cytochrome-b₆f complex, and antenna pigment complexes. At the same time, BMAA led to an increase in the amount of cytochrome c₆.

E. Senatskaya et al. (Saint Petersburg State University) presented results of advanced assessment of cyanobacteria producing red-shifted pigments, in particular chlorophylls with an absorption peak in the range of 700–750 nm. The section also discussed the dynamics of light absorption by plant leaves under various spectral characteristics of the light environment (Dr. T. Kuleshova et al., Ioffe Physico-Technical Institute and Agrophysical Institute, St. Petersburg), the role of viral glycosylases of pyrimidine dimers in evolution of marine microbiota genome sequences (A. Karmanova et al., Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino) and other issues related to the use of photobiological methods for studying the state of ecological systems.

In general, the work of the section showed that the fundamental knowledge about the organization and mechanisms of regulation of the photosynthetic apparatus in various conditions gained over the past decades is currently being actively applied in automated measurement of the dynamics of indicators of the photosynthetic activity of green plants and algae. Automated processing of the large generated datasets by machine learning methods will allow continuous monitoring of photobiological features as indicators of the ecological state of both terrestrial and aquatic ecosystems. Particular success has been achieved here with the use of microalgae as bioindicators. Thus, the presentations of the section demonstrated the capabilities of photobiological methods in solving practical problems of environmental monitoring.

An active discussion of the presentations at the meetings and informal discussions between sessions allowed the participants of the Congress to share their experience, to discuss new solutions to common problems, to establish new contacts, and to strengthen old ones.

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The authors declare no competing interests.