Ecological Systems and Devices Annotation << Back Seasonal Dynamics of Fluorescent Parameters of Primary Productivity as an Initial Stage of Carbon Flux at the Gelendzhik Carboniferous Polygon in the Black Sea Mosharov S.A., Fedorov A.V., Sashova O.A., Dallakyan G.A., Mosharova I.V. This study, conducted for the first time, examined the seasonal dynamics of fluorescent parameters of primary productivity (minimum fluorescence, F0 , quantum efficiency of photosynthesis, Fv /Fm, and electron transport rate in photosystem, rETR) with a high temporal resolution of 2–3 days at the Gelendzhik Carbon Polygon in the Black Sea. Significant short-term (3–10 days) variability in the F0 parameter (an indicator of chlorophyll a concentration), moderate variability in Fv /Fm (potential photosynthetic capacity), and rETR (a measure of primary production) were identified. A general increase in photosynthetic capacity (Fv /Fm and rETR) was detected during the summer period (from late May to late August), which included two phytoplankton blooms (spring and summer), with a maximum during the summer bloom in late July. In the climatic aspect, the high potential of phytoplankton productivity and, accordingly, the initial stage of carbon flux, which manifests itself during the spring-summer period, is realized to the greatest extent during the summer bloom period. Keywords: active chlorophyll fluorescence, quantum efficiency of photosynthesis, electron transport rate, phytoplankton, Black Sea. DOI: 10.25791/esip.12.2025.1565 Pp. 56-66.