The features of the species, spatial, and trophic structure of macrobenthic sublittoral communities were studied in two coastal lagoon ecosystems of the White Sea. The Ermolinskaya and Nikol’skaya inlets are highly silted lagoon ecosystems with a simplified trophic structure of the macrobenthos community and a predominance of the trophic group of collecting detritophages. In the sublittoral of the studied lagoons, 24 species of invertebrates, as well as four species of marine higher plants and algae (Zostera marina, Cladophora sericea, Fucus vesiculosus, and Chorda tomentosa), were found. The lagoon ecosystem of the Ermolinskaya Inlet was characterized by the highest species diversity, total density, and biomass of species populations of macrobenthos, while the ecosystem of the Nikol’skaya Inlet was characterized by lower indices. In the lagoon of the Nikol’skaya Inlet, which was better protected from the sea waves and currents, a greater development of littoral euryhaline marine and brackish-water species of macrobenthos was observed, while more marine sublittoral species were found in the lagoon of the Ermolinskaya Inlet, which is less protected from the sea.