The coupling of numerical geophysical models of a sea with marine ecosystem models is considered. For the latter, BFM was chosen and coupled with three Russian models for three seas of different spatial scales: the White Sea (JASMINE), the Arctic Ocean (FEMAO), and the global ocean as a part of the Earth system (INMCM). We describe technical details of implementation and discuss important questions of the computing efficiency and sensitivity of the model to the sea-ice subsystem and boundary values. The ecology model can simultaneously embrace pelagic, benthic, and sympagic ecosystems.