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Wednesday, April 15, 2015

Blue crate special

On 9 April 2015, we noticed a blue crate washed ashore covered with pelagic gooseneck barnacles (Lepas sp.):

We didn't have a lot of time, but we noticed that some of the barnacles had an unusual purple coloration between their plates:

For the record, here's a close-up (see below).  We're not sure if the purple had actually been incorporated into the plates, or if there was an internal structure with that color that was strong enough to show through the plates.  Do you have ideas about what could cause this coloration?

I don't know if they have responded to the warmer water during the past year, but there have been impressive numbers of pelagic gooseneck barnacles on objects washing ashore during the past month.


John W. Wall said...

What's all that honeycomb stuff? I see something like that on intertidal zone rocks and have been wondering. I didn't used to notice so much of it and wondered what's going on and whether it's related to the absence of sea star predation.

Jackie Sones said...

Hi, John!

The "honeycomb stuff" is a bryozoan colony. You can see similar patches up close in a couple of previous posts:



If you are seeing more bryozoans, it's a little hard to know for sure why would that would be. Have they had "good years" for reproduction? Could that be related to food? Temperature? Water currents? Has something opened up more substrate for them? (And note bryozoans on rocks are generally more visible when algae is in its early growth stages, in the winter and early spring, for example.) If it's related to predation, which predator? When it comes to bryozoans, seastars aren't the first predators I think of...but maybe something like a nudibranch? If there was less seastar predation at a site, that might result in more mussels, which could reduce the rock surface available for bryozoans (although I often think of bryozoans growing at lower tide levels than mussels). Lots of things to consider, and it's interesting to keep track at local sites and to explore ideas!

John W. Wall said...

Wow, I've got to take a closer look next time I see that.