In any local seaweed forest or on drifting kelp patties you can see white patches covering the kelp blades. Those white patches are actually colonies of an animal called the lacy crust bryozoan or Membranipora membranacea. A bryozoan is a colonial animal composed of interconnected genetically identical individuals called zooids. The individual zooid is not much more than a millimeter in length and contains a live animal that reaches out with a ring of tentacles to filter feed in the water. Close-up, the animal looks similar to a small anemone or coral polyp, but is not related to those species. Membranipora is an epiphytic bryozoan, meaning it lives on the surface of algae species. It is particularly common on large brown kelp species. The white patches you can see are Membranipora colonies that asexually produce more zooids to expand and encrust the blades and in some cases can cover almost 100 percent of the seaweed .
By living on the fronds of seaweed, the colonies are higher up in the water column and have greater access to phytoplankton and small particles of detritus that they feed on. At high densities, the presence of the colonies can increase tearing of kelp blades, but under moderate conditions, the colonies do not appear to have a negative effect on seaweed , and supplies the algae with a source of nitrogen.
Colonies live for approximately six weeks and become most dense on kelp in late spring and die back with the kelp as the summer warm-water currents arrive. During fall, you can see the Membranipora colonies on almost any piece of drift kelp washed up on the beach.