ESTIMATION OF THE VERTICAL CARBON FLUX ASSOCIATED WITH THE RESPIRATION OF MIGRATING COPEPODS CALANUS EUXINUS AND PSEUDOCALANUS ELONGATUS IN THE BLACK SEA

Diel vertical migrations of zooplankton make a significant contribution to the functioning of the biological pump by providing active transport of carbon from surface layers to depth. In the Black Sea, quantitative assessments of this process have not been carried out until now. In this work, for the first time, calculated values of the carbon flux associated with the respiration of two mass species of migrating copepods, Calanus euxinus and Pseudocalanus elongatus, were obtained. The study was conducted at 13 daily stations in the northern and northeastern parts of the Black Sea from April to September 2020–2021 (cruises No. 114, 116, 118 of the R/V “Professor Vodyanitsky”). To estimate the carbon flux, we used: (1) expedition data on the daily dynamics of the vertical distribution of copepod abundance and biomass; (2) the Vinogradov’s migration coefficients obtained on their basis, characterizing the intensity of vertical movements of organisms; (3) calculated values of the intensity of their respiration, taking into account the water temperature and the time spent by them at depth during daylight hours. It was shown that the main contribution (up to 90 %) to the studied carbon flux was made by females and fifth-stage copepodites of C. euxinus. The values of the total flux increased from the spring minimum of 0.14 mmol C·m-2·day-1 in April to a maximum (0.46 mmol C·m-2·day-1) in September. The results obtained may indicate an important role of diel vertical migrations of zooplankton in the functioning of the biological pump of the Black Sea. The relevance of further studies of the seasonal and interannual dynamics of zooplankton migrations and associated fluxes, as well as their response to changes in climate and hydrological conditions in the Black Sea, is emphasized