Why are sponges important members of deep-sea bottom communities?

Sponges are vital members of deep-sea bottom communities, or benthos, primarily due to their complex structural roles and their extensive associations with other marine life.

As sessile organisms, sponges provide essential microhabitats for a diverse array of species. Their intricate internal systems of canals and cavities serve as shelters or permanent homes for thousands of organisms, including crustaceans, nematode and polychaete worms, brittle stars, and bivalve mollusks. This capacity to host such high biodiversity makes them foundational to the environmental microclimate of the seafloor.123

Furthermore, sponges are ecologically significant because they can dominate certain environments, sometimes covering vast areas of rocky overhangs or deep-sea bottoms. By modifying their immediate surroundings, they provide protection against extreme fluctuations in physical factors like temperature and light, thereby supporting the survival of other organisms in the community. Their presence is so pervasive that certain classes, such as Hexactinellida, are considered characteristic of the deepest muddy ocean regions.43