The work aims at construction of chlorophyll a fields based on variational assimilation of available satellite information for a few days in a transport model. Such information is the most real-time, but most often it has omissions (sometimes significant) in its structure due to the scattering effect of clouds, glares, etc. Therefore, obtaining reliable fields taking into account the available information for the Black Sea is an important and urgent task. In the numerical implementation of the transport model and variational method of measurement data assimilation, the results of calculations based on the MHI dynamic model for the Black Sea were used. In the numerical implementation of the variational assimilation algorithm, iterative gradient methods are used, and the solution of the adjoint problem is used to construct the gradient of the cost function in the parameter space. As a result of the calculations, a field of chlorophyll a concentration was obtained for almost the entire Black Sea area consistent with the measurement data. The paper implements a variational algorithm for the satellite information assimilation, which made it possible to obtain a chlorophyll a concentration field for the Black Sea area, taking into account incomplete coverage with observational data. The procedure can be used to determine concentration fields of various suspended substances in the sea based on data distributed over time and space.