Almost every year, patches of shiny black or blue-black juvenile Mytilus* appear among the acorn barnacles on exposed rocky shores. Unfortunately, the patches don’t last long. Their vulnerability to predatory snails may partially explain their failure to persist.
*In 2018, when I composed this post, I thought the patches of juveniles must be Mytilus trossulus, but I’ve learned there’s a good chance they are M. californianus.
Blending In – or Standing Out?
I updated this post on August 16, 2022, to reflect my uncertainty about the identity of the mussels.
theoutershores 
Oh, I love these – nice shot as well. The patches in themselves stand out, but also that brownish one.
So sorry I forgot to reply to your note about how the patches of black mussels stand out too. Such a good observation. I had a fleeting thought of it while preparing the post, but it slipped away. Thanks for bring it back for me!
You are welcome!
There always has to be at least one in every crowd! 😀
Ha! so true. At least one. Apologies I forgot to get back to you ’til now. Thanks!