Posidonia oceanica rhizomes are overgrown with a large-scaled colony of the moss animal, that firstly has been mistaken for a rag of stockinet.
Separate single individuals are settled in every cell of the colony. They let out the pecten bearing ciliated tentacles called lophophore, that is used by bryozoa for catching organic particles suspended in the water. At the image, tentacles look like a white fuzz covering the settlement.