We examined microbial communities from two developmental stages (adult and larvae) of two species of carotenoid-rich sponges (Clathria prolifera and Halichondria bowerbanki) from the mid-Atlantic region of the eastern United States. We relate the host:symbiont dynamics observed to current understanding of transmission dynamics in sponge microbial communities, compare our findings with other surveys of bacterial symbiont diversity in sponges, and discuss results in the context of the holobiont phenotype.