A local naturalist, in the comments to my previous post, suggested that the creatures we photographed may have been tunicates, possibly Ciona. Thanks, Hugh.
I have spent most of the evening looking at photos of tunicates of this area, and reading what I could find on their locations. Hugh could be right; Ciona looks possible.
There are five invasive species of tunicate in the area, Ciona savigny, Styela clava, Didemnum sp., Botrylloides violaceus, and Botryllus schlosseri; of these, only Ciona looks like it may match. The colour is right, the shape is almost right, and some of the groupings show circles that may be siphon mouths.
Two similar native species, Corella inflata and Corella willmeriana, are smaller and rounder. They don't match mine. Besides, Corella inflata dies within a few days if exposed to sunlight.
Many tunicates eat anenomes, but Ciona savigny is a filter feeder, eating bits of waste. There are obviously no anenomes on this kelp.
Most of the tunicates live at greater depths, out of the sunlight, but a few are found under docks and floats. Most of them, including Ciona, fasten to firmer ground, though; pilings, rocks, even mussels. These were on kelp.
A couple of the things look definitely like Melibe leonina, which is transparent and usually found on eelgrass. I found one mention of it on kelp.
Several of the other shapes could be Melibe, as well, either singly or in groups. Do Melibe hang out together in flocks? Or could this be a mixed bag, Melibe and Ciona? Do they mix?
And should I report these as invasive species? And to whom? The address I have is for across the border.
Every question leads to a list of questions, doesn't it?