Ecologica Montenegrina, 34, 2020, 20-33 Сarbon fluxes intensity from substrates and phototrophic consortiums of the photic zones in Montenegro caves SVETLANA E. MAZINA 1,2 , EKATERINA V. KOZLOVA 1 , SOFIIA M. TURCHINSKAYA 3 , ELIZAVETA K. PICHUGINA 1 , AKHMED K. YUZBEKOV 4 & VLADIMIR PEŠIĆ 5 1 Department of Ecological Monitoring and Forecasting, Faculty of Ecology, Peoples’ Friendship University of Russia (RUDN University), 117198, 6 Miklukho-Maklaya Street, Moscow, Russian Federation 2 Department of Radiochemistry, Faculty of Chemistry, Lomonosov Moscow State University, 119991, 1-12 Leninskiye Gory, Moscow, Russian Federation 3 Laboratory of Radiocarbon Dating and Electron Microscopy, Institute of Geography, Russian Academy of Sciences, 119017, 29-4 Staromonetnyj pereulok, Moscow, Russian Federation 4 Department of Plant Ecology and Geography, Faculty of Biology, Lomonosov Moscow State University, 119991, Moscow, 1-12 Leninskie Gory, Moscow, Russian Federation 5 Department of Biology, Faculty of Sciences, University of Montenegro, Cetinjski put b.b., 81000 Podgorica, Montenegro *Corresponding author: ekaterina.vi.ko@gmail.com Received 21 June 2020 │ Accepted by V. Pešić: 4 August 2020 │ Published online 6 August 2020. Abstract Сarbon dioxide fluxes from substrates and consortiums were estimated for the first time in the photic zones of seven caves of Montenegro. The dependence of consortiums productivity with their species composition and structure, as well as determination of the priority source of carbon dioxide for the primary producers of trophic chains of the photic zones were revealed. Five consortiums were distinguished in the fouling communities of the photic zones of seven karst caves of Montenegro: with the dominance of acrocarpous mosses, pleurocarpous mosses, green algae, cyanobacteria biofilms and sheath-forming cyanobacteria on various substrates. The closed chamber technique was used to calculate carbon fluxes. The net carbon flux, gross respiration of substrates and consortiums, and gross primary production of consortiums in the summer and winter were determined. The biomass of the phototrophic and heterotrophic components of the consortiums was estimated. Isotopic analysis of clay deposits and phytomass of bryophytes in the consotriums as well as on the surface was carried out. All of the investigated consortiums function as a carbon sink in both seasons, providing a negative balance to the atmosphere. Consortiums with the dominance of bryophytes possessed the greatest biomass, spores of micromycetes dominated in the heterotrophic component. The respiration of substrates was maximized on clay deposits, the respiration rate increased in winter. Phototrophic respiration and gross primary production were maximal in the consortiums of acrocarpous mosses and case-forming cyanobacteria in terms of dry phytomass. Increased content of the light carbon isotope 12 C in the bryophytes phytomass in the photic zones compared to the bryophytes phytomass on the surface was established. Key words: karst caves, ecotones, carbon balance, stable isotopes. Ecologica Montenegrina 34: 20-33 (2020) This journal is available online at: www.biotaxa.org/em http://dx.doi.org/10.37828/em.2020.34.3