Purpose. The work is purposed at studying the spatial distribution, temporal variability and fluxes of particulate organic matter in the Black Sea based on numerical modeling.

Methods and Results. A model of the lower trophic level of the Black Sea ecosystem is applied to estimate the spatial distribution and vertical fluxes of particulate organic matter in the upper 200-meter layer. To extend the study to the whole thickness of the Black Sea, a model consisting of an equation for the evolution of particulate organic matter concentration in the layer from 200 m to the bottom was developed. The hydrodynamic and thermodynamic fields obtained from the previous reanalysis are used as coefficients in this equation and in the equations of the ecosystem model. The modeling was carried out for the period 2016–2020. The concentrations and vertical fluxes of particulate organic matter are obtained on a regular grid and with a time resolution of 1 day. The particulate organic carbon fluxes derived from numerical modeling are compared with the results of processing the samples collected by the sediment traps at two points in the Black Sea. The simulation results are in a fairly good qualitative and quantitative agreement with the measurement results.

Conclusions. A model for calculating the particulate organic matter content in the deep layers of the Black Sea was developed. The modeling results have shown that due to the biological processes, the particulate organic matter concentration in the surface layer of the Black Sea significantly exceeds that in the deep-sea layer. The magnitude of vertical particulate organic matter fluxes in the surface layer is conditioned mainly by the suspended matter concentration, whereas in the deep-sea layer – by the value of vertical velocity. Based on the modeling results, the carbon flux directed from the water column to the bottom was evaluated as a result of suspended matter settling. The main part of this flux falls on the shelf zone of the sea.