What's this stuff that looks like white chainmail armor growing on giant kelp? I found some giant kelp coated with a material that is white, smooth, and forms a chain-mail pattern with small black oblong lumps in between the links. It feels pretty hard but not stiff (the kelp still flexes), and can't be easily removed from the kelp skin. The leaves under the coating appear to be stunted and malformed. This was found in the Pacific in Southern California in the late summer. ![Giant kelp with an unusual bumpy coating]( I took a photo with a low-quality microscope. ![Microscope photo of kelp with bumpy coating]( Is it a parasite?

That looks like it could be the lacy crust bryozoan ( _Membranipora membranacea_ ). That bryozoan is an epiphytic animal whose native range includes the Pacific coast; it does not feed on the kelp, but can weaken and damage it when abundant 1. Whether you should call this a parasite seems somewhat definitional and is something I'll leave to an ecologist to answer.

For comparison see the following public domain image from the USGS: ![bryozoan \(Membranipora membranacea\) encrusting kelp — USGS,

Apparently photographed by: Eugene van der Pijll

In addition to the wikipedia article, you may also find this page from the Texas Invasive Species Institute to be of interest.

#### References:

1. North, W. J. (1976). Underwater California (No. 39). University of California Press.