According to the University of Wisconsin La Crosse, sponges can reproduce asexually through external budding, gemmules (or internal budding) and the regeneration of broken pieces that develop into full-bodied sponges themselves. Sponges can also reproduce sexually.
The external budding method of asexual reproduction involves a young, immature sponge forming at the outer base of the sponge. These buds can split off entirely and become a separate sponge, or they can stay put near their parent sponge to form a sponge colony.
According to the University of California at Berkeley, the gemmules method of asexual reproduction is more common for sponges. Gemmules are essentially a packet of internal buds in the form of cells that are nestled inside a protective coating. They can be released when the parent sponge dies, usually due to bad conditions, including seasonal cold. The gemmules can then exist within the protective packet until conditions improve, at which point they establish and mature into sponges.
Finally, because sponges have regenerative powers, particles that break off from an established adult sponge may eventually develop into a living sponge. The sponge from which the particle broke off will regenerate its tissue to replace the lost piece that is now developing into a new sponge.