Anyone know what is happening in this pic?

[tmulrney]

The coralline on the rock is....receding? It used to cover the rock. What the heck?

 

[RtReef]

Could have something feeding off the algae and casuing it to recede??? I think those little 4 arm starfish eat coraline?

 

[tmulrney]

Could have something feeding off the algae and casuing it to recede??? I think those little 4 arm starfish eat coraline?

I don't thinks so because it is happening so uniformly. That light pink line the separates the algae from the bare rock is traveling down the rock.

 

[big-Ern]

I've had tons of those stars and they leave little spots where they sit and eat the algae, not a mass area like that. I've also had urchins chow through coraline, but again never all in one area like that. I had a emarld that loved to scrape the rocks and would take from one specific area, but you could really make out that it was more scratched than so uniformly removed.

 

[marke]

Could it be high alkalinity

 

[tmulrney]

Could it be high alkalinity

Alk is 10.8

 

[tmulrney]

Calcium normally is 450-460 but went down to 327. It's corrected now. Weird thing is, the erosion is happening only on that one rock. The rest of the rocks are covered in coralline.

 

[reef cuber]

I know this is an old post, but I found my largest emerald crab breaking the coralline off my coral/rocks, and was shoving it in his mouth. He was either hungry or deficient in something I'll wager. Thought I would share what I saw.