This Membranipora serrilamella
or Kelp-encrusting Bryozoan is growing on kelp this time of year. This piece of kelp, found during the minus tide growing on a huge rock, was about 5"" wide and probably 6' long or longer, and was covered with colonies of bryozoans. Apparently each colony begins in the center of each circle and grow outwards. The second photo shows detail with my macro lens.