Some of you might have noticed in the Comments section that Matt won the prize — he guessed correctly that these patches are dense concentrations of pelagic barnacle cyprids. Recall that cyprids are the final larval stage that settles out of the plankton. In this case, these are the cyprids of a pelagic gooseneck barnacle called Lepas sp.
Here's a close-up of the cyprids under a microscope:
After settling on a floating substrate, the cyprids will undergo metamorphosis into juvenile barnacles. A few of them had already done so:
I wanted to post these pictures on the blog because there have been amazing numbers of Lepas cyprids this year — more than any other year since I've been observing floating objects washing ashore in Bodega Bay. I've wondered if it could be related to the warm water temperatures last year, but we can't be certain.
What's perhaps even more fun, though, is that when I went to take these documentary pictures, I noticed a few other things among the cyprids!
At first I thought this was just a blue tentacle (perhaps from Velella)...but then it started moving...and then I noticed the eye spots at the anterior (front) end. A tiny blue ribbon worm! I'd never seen a blue ribbon worm before.
One time the ribbon worm left one patch of cyprids and crossed the great divide to another patch of cyprids. If anyone has thoughts about the identity of this ribbon worm, I'd love to hear more.
When I was scanning the cyprids, I also noticed quite a few small light brown spots. If you look very carefully, you'll see them in the lower left corner of the next photo, nestled among the cyprids:
When I zoomed in, I could see that these brown spots were moving, that they had dark eyespots, and that they might have some sort of paired structures forming on their heads (see small bumps in image below).
Although I'm uncertain, my best guess for these little brown blobs is that they could be very young pelagic nudibranchs (Fiona pinnata). I've written about Fiona before (see post on 19 October 2012), but I've never seen one this small, hence my uncertainty. What do you think? Do you have a different guess?
The Sea Palm and Lepas cyprids reminded us of a valuable lesson — it's always worth taking a closer look!