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The Lorax for the Kelp Forest
Scuba Legend
Reaction score
Santa Catalina Island, CA
# of dives
2500 - 4999

Many dwellers of the terrestrial portion of Planet Ocean are not well-versed in the critters of the 70% of our planet covered by water. Why else would the PC crowd have to rename starfish as sea stars, jellyfish to sea jellies, etc., etc? Anyone who passed basic high school biology should know the difference! Any why has the PC crowd not complained about fish called by other animal names... hopefully no one confuses a sheephead with a wool-bearing critter or a halfmoon with our celestial satellite!

Many divers are quite knowledgeable about the critters they encounter within recreational dive depths. I am often impressed with their knowledge about the sea. However, there are a few groups that many are relatively uninformed about. Here is where my professional training and 60 years on SCUBA have equipped me to "edumacate" fellow denizens of King Neptune's briny depths.

One such group is the bryozoa or moss animals. Perhaps it is simply because many of them are rather small and divers without prescription lenses may only see them as a fuzzy image. We're talking about large colonies of these critters being small... each colony is composed of very tiny individual;s known as zooids that are encased in a calcareous or chitinous chamber known as a zooecium. You need a microscope to see them (and fortunately I have five of those in my well-equipped lab... er living room).

Bryozoa are somewhat unique in that they are almost all sessile (bottom-dwelling) organisms that feed using a structure known as a lophophore composed of a crown of tiny tentacles. They lie in wait for unsuspecting bacteria, plant plankton and (yuck) detritus to pass by. Often some of the zooids have specialized functions such as reproduction, defense of the colony or attachment to the substrate.

This phylum utilizes two different reproduction strategies. New colonies form when larvae, created by sexual reproduction, disperse in the plankton to new locations. Once settled, the colony grows through asexual budding.

As for species identification, the non-specialist cannot rely strictly on the morphology of the colony... and, of course, I'm no "ex-spurt" on this group. There are over 300 species along the Pacific West Coast according to Jensen, et al., Beneath Pacific Tides (a highly recommended guide to our critters). Most require a microscope to ID properly, but I'll focus on a few that are fairly easy to determine.

One of the most commonly seen species of bryozoa can be easily spotted even by the vision-challenged. I'm referring to the jack frost bryozoan, Mermbranipora, that forms white patches on mature kelp blades. It was the very first genus of moss animal that I learned way back in my freshman marine biology seminar at Harvard. Therre are a number of different species in the genus but a common one here is M. villosa.

A favorite of mine is the lacy bryozoan, Phidolopora pacifica, which ranges from British Columbia to the Galapagos. Colonies are composed of fluted structures that have numerous holes in them. These structures can be relatively large for a bryozoan species, up to as much as 8" across.

A third one I commonly encounter is the southern staghorn bryozoan, Diaperoforma californica. No self-respecting deer would be threatened by the tiny "staghorns" on this moss animal. It, too, can reach easily detectable sizes of up to 12" across. This species is known from British Columbia to the Los Coronados Islands south of the border.

And last (but not least) is Bugula neritina. The reddish or purplish color is unique. This species is found from Monterey to Panama and the Galapagos. It can be extremely common in our waters, often completely overwhelming the blades of giant kelp causing them to sink. It may surprise many (including yours truly) to learn that this species is not native, but introduced!

© 2021 Dr. Bill Bushing. For the entire archived set of nearly 900 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page

Image caption: Membranipora on kelp blades and a close-up under my microscope; Phidolopora and Diaperoforma; and Bugula neritina on kelp blades.

DDDB 896 bryozoa sm.jpg

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