small round dark "bubbles" on rocks

[mikebusc]

What are these small dark bubbles. Actually a few are bigger. Like 1/2 a marble big. But most are small.

 

[Tahoe61]

Bubble Algae. Emerald Crab or manual removal.

 

[jabberwock]

Agree, try not to pop them if manually removing.

 

[mikebusc]

Bubble Algae. Emerald Crab or manual removal.

A couple of emerald crabs did the trick. Thank you!