Bryozoans in the Mediterranean Sea are recognized as bioconstructional framework builders, both primary builders that construct frameworks alone or in combination with other organisms, or secondary builders that play various functional roles. Ten bryozoan species or complexes of species in the Mediterranean are responsible for providing habitats for diverse species and assemblages, thus playing important roles in promoting biodiversity and habitat heterogeneity. Four habitat-forming bryozoans respond to climatic changes (global warming and ocean acidification) by altering their colony growth, zooidal morphology and development, skeletal mineralogy and geochemistry. Under conditions of reduced pH, these species reallocate energy resources within the colony by regulating zooid size, proportion of polymorphs, number of zooidal generations, colony growth rate, and investment in the organic components involved in biomineralizational processes. Mediterranean 'bryo-constructions' are suitable 'ecosystem models' to be monitored in the context of climate change, especially ocean acidification and warming. © 2014 Springer Science+Business Media Dordrecht. All rights are reserved by the Publisher.