Dreissena spp. tend to be the dominant invertebrates both in density and biomass in benthic communities, with their introduction often leading to the displacement of indigenous species (Karatayev et al. 1997). Attachment to a suitable substrate is essential to completion of their life cycle, but other organisms, however, have been reported to be capable of excluding Dreissena from substrates. Sponges, especially on vertical surfaces, can overgrow and kill Dreissena spp. by impairing normal mussel feeding and respiration (Ricciardi et al. 1995, Early and Glonek 1999). Other benthic organisms recorded as successfully outcompeting dreissenids include amphipods, algae, bryozoans, hydrozoan coelenterates, and other bivalves (Molloy et al. 1997).
Sponges, visible here as the yellow and green areas, are in the process of overgrowing a zebra mussel colony (Photo: T. Lauer).